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ERGONOMÍA OCUPACIONAL

INVESTIGACIONES Y APLICACIONES

VOL. 3

SOCIEDAD DE ERGONOMISTAS DE MÉXICO A.C. (SEMAC)

2010

ERGONOMÍA OCUPACIONAL

INVESTIGACIONES Y APLICACIONES

VOL. 3

EDITADO POR:

CARLOS ESPEJO GUASCO Presidente Fundador SEMAC ENRIQUE DE LA VEGA BUSTILLOS

Presidente SEMAC 2002-2004

VICTORIO MARTINEZ CASTRO

Presidente SEMAC 2008-2010

2010 Sociedad de Ergonomistas de México A.C. (SEMAC) ISBN 978-0-578-05757-6

Prefacio

La Sociedad de Ergonomistas de México A.C. (SEMAC), como parte relevante de su actividad e interés en la difusión, promoción y apoyo a la ergonomía, ha organizado desde 1999 y de forma anual, su Congreso Internacional de Ergonomía. En Mayo de 2010, el XII Congreso Internacional de Ergonomía tiene lugar en CD. Juárez, Chih., con la participación de ergonomistas profesionales e interesados en esta área.

Aunque este último año ha sido, económicamente, muy difícil, eso no ha disminuido la calidad de los trabajos que se presentan este año. Se reúnen en este libro una selección de los trabajos, presentados en este congreso, más representativos de las diversas áreas que participan en la ergonomía, aportando diferentes investigaciones y soluciones a problemas específicos, con la finalidad de contribuir a la difusión, apoyo en la educación e investigación, de temas de interés para la ergonomía.

Los editores, árbitros y comité académico, a nombre de la Sociedad de Ergonomistas de México, A.C., agradecemos a los autores de los trabajos aquí presentados su esfuerzo, e interés por participar y compartir su trabajo y conocimientos en el XII Congreso Internacional de Ergonomía de SEMAC. También agradecemos a los participantes y asistentes, provenientes de muy diversos lugares y formaciones, así como a todo el equipo de organización de este congreso, su valiosa aportación que estamos seguros derivará en el avance de la ergonomía en las Instituciones de Educación Superior y en la planta productiva nacional y mundial.

Enrique de la Vega Bustillos

Presidente SEMAC 2002 – 2004

SOCIEDAD DE ERGONOMISTAS DE MÉXICO A.C.

“Trabajo para optimizar el trabajo”

Cd. Juárez, Chih. Mayo de 2010

Ergonomía Ocupacional. Investigaciones y aplicaciones:. Vol 3

1

CONTENT ANTHROPOMETRY Page ANTHROPOMETRIC DATA OF STUDENTS OF THE UNIVERSITY OF SONORA, SONORA, MEXICO Martina Elisa Platt Borbón, Amina Marín Martínez, María Magdalena Ayala, Rafael Castillo Ortega and Félix Montaño Valle

1

ANTHROPOMETRY AND FACILITIES DESIGN VERIFICATION OF NEW DEVELOPED PRESCHOOL LEVEL BUILDINGS IN THE EDUCATIONAL SECTOR OF HERMOSILLO, SONORA. Hiram Jesús Higuera Valenzuela, Manuel Sandoval Delgado DESIGN ANTHROPOMETRIC REFERENCED LETTERS TO THE LABOR POPULATION OF CABORCA CITY IN SONORA MEXICO. Joaquín Vásquez Quiroga, Jesús Rodolfo Guzmán Hernández, Enrique Javier de la Vega Bustillos.

14

20

BIOMECHANICAL BIOMECHANICAL MODEL TO ESTIMATE RECOVERY TIME ON HIGHLY REPETITIVE WORK IN MAQUILA OPERATIONS Fco. Octavio López Millán, Enrique Javier de la Vega Bustillos, Manuel Arnoldo Rodríguez Medina, Armando Ayala Corona VERIFICATION OF MAXIMUM ACCEPTABLE WEIGHT OF LIFT, TABULATED IN LIBERTY MUTUAL TABLES, IN WOMEN OF CABORCA Jesús Rodolfo Guzmán Hernández, Joaquín Vásquez Quiroga, Enrique Javier De La Vega Bustillos FORCE ANALYSIS IN HANDS ON HIGHLY REPETITIVE WORK IN MAQUILA OPERATIONS Fco. Octavio López Millán, Enrique Javier de la Vega Bustillos, MaríaJesúsTéllez Moroyoqui, LodevarPavlovichOviedo, Bertha Leticia Ortiz Navar

35

46

55

DESIGN AND WORK ANALYSIS ADVANTAGES OF THE ORTHOGONAL ARRANGEMENTS OF THE METHOD TAGUCHI IN THE DESIGN OF EXPERIMENTS IN ERGONOMIC Alois Fabiani-Bello, Humberto García-Castellanos, Rosa Maria Reyes Martinez

76


ERGONOMICS AND EDUCATION ACADEMIC ASSAYS FOR ERGONOMICS. Zoe Madai Cruz Purata, María del Sagrario Medina Rodríguez, Julio Gerardo Lorenzo Palomera

86

OCCUPATIONAL ERGONICS ANALYSIS OF CORRELATION BETWEEN THE VARIABLES OF TEMPERATURE, STRENGTH AND CYCLES PER MINUTE TO PERFORM HORIZONTAL REPETITIVE MOVEMENTS OF THE WRIST Camargo Wilson Claudia, Rivera Valerio Abril A., Rubio Martinez Jesus R., de la Vega Bustillos Enrique J., López Bonilla Oscar R., Olguín Tiznado Jesús E., Báez López Yolanda A.

98

TEMPERATURE ANALYSIS ON WRIST SURFACE DUE REPETITIVE MOVEMENT TASKS USING SENSORIAL THERMOGRAPHY TO FIND OUT A POSSIBLE PATHOLOGY FOR A CTD Ordorica Villalvazo Javier, Camargo Wilson Claudia, De la Vega Bustillos Enrique, Olguín Tiznado Jesús E., López Bonilla Oscar R., Limón Romero Jorge

114

VIBRATION STUDY TO IMPROVE STRIPPING OPERATION IN A LITOGRAPHICS COMPANY Mario Ramírez Barrera, Jorge Valenzuela Corral, Athenea Núñez Sifuentes

128

A DESCRIPTIVE STUDY ABOUT THE INTEGRATION OF ERGONOMIC ATTRIBUTES ON THE SELECTION OF ADVANCED MANUFACTURING TECHNOLOGY -AMT- Aidé Maldonado Macías, Arturo Reallyvázquez, Guadalupe Ramírez, Jorge Garcia-Alcaraz, Salvador Noriega

137

WORK EVALUATION REMOTE ERGONOMICS EVALUATIONS IN THE OFFICE Jeffrey E. Fernandez, Gabriel Ibarra-Mejia , and Brandy F. Ware

151

COMPARATIVE ANALYSIS BETWEEN AN ERGONOMIC EVALUATION AND THE USERS' SATISFACTION OF NEW EDUCATIONAL CENTERS Martín Daniel Del Sol Rangel, Manuel Sandoval Delgado

156

DESIGN AND IMPLEMENTATION OF MANUFACTURING CELL WITH ERGONOMIC SUPPORT ANALYSIS Rigoberto Zamora Alarcón, Manuel Enrique Alcaráz Ayala, Julio César Romero González

163


COMITÉ ACADÉMICO

ROSA MARIA REYES MARTINEZ Instituto Tecnologico de Cd. Juarez

MONICA AIDE BARRERA Delphi, Cd. Juarez

AIDE ARACELY MALDONADO MACIAS Universidad Autonoma de Cd. Juarez

ELISA CHACON MARINEZ Nchmarketing, Cd. Juarez

MA. ANTONIA BARRAZA Createc Cd. Juarez

CARLOS ESPEJO GUASCO Visteon, Cd. Juarez

JEAN PAUL BECKER Ergon, Guadalajara, Jal.

FRANCISCO OCTAVIO LOPEZ MILLAN Instituto Tecnologico de Hermosillo

GABRIEL IBARRA MEJIA Universidad Autonoma de Cd. Juarez

VICTORIO MARTINEZ CASTRO MABE

MIGUEL BALDERRAMA CHACON Valeo, Cd. Juarez

Ergonomía Ocupacional. Investigaciones y Aplicaciones. Vol 3 2010

Sociedad de Ergonomistas de México, A.C. 1

"ANTHROPOMETRIC DATA OF STUDENTS OF THE

UNIVERSITY OF SONORA, SONORA, MEXICO"

Martina Elisa Platt Borbón, Amina Marín Martínez, María Magdalena Ayala,

Rafael Castillo Ortega and Félix Montaño Valle

Industrial Engineering Department, Universidad de Sonora, Sonora, México

[email protected],[email protected],[email protected],4rcastillo@industrial.

uson.mx,[email protected]

RESUMEN Las cartas antropométricas dan la información acerca de las dimensiones de una población determinada y

son muy utilizadas por los diseñadores. Los expertos en diseño afirman que una ayuda física diseñada

para una población especifica, no es óptima para cualquier otra; ésto parece lógico, pero en nuestro país,

no es posible ratificar o rectificar esta afirmación debido a que desconocemos las Cartas Antropométricas

Mexicanas.

La antropometría es la determinante de las condiciones ergonómicas; por tanto, los estudios

antropométricos deben referirse a una población específica y de ahí nuestro interés por conocer las

medidas de los estudiantes de la Universidad de Sonora.

Se incluye un ejemplo de las tablas antropométricas por edad y por sexo de un estudio realizado a 227

estudiantes de la Universidad de Sonora, Unidad regional Centro y se describe la metodología utilizada.

ABSTRACT

Anthropometric data gives information about the dimensions of a certain population and it is used by

designers. Design experts affirm that physical equipment and facilities designed for a specific population,

are not good for any other one; this seems logical, but, in our country, it is not possible to ratify or to rectify

this statement because many of us ignore the Mexican Anthropometric data.



In order to design ergonomic living and working conditions, anthropometric principles must be applied;

therefore anthropometric studies should refer to a specific population and it is our interest to know the

dimensions and some physical features of the students of the University of Sonora.

This research contains data collected in a sample of 227 students of the University of Sonora, Sonora,

Mexico, from January to December, 2009; their body dimensions by age and sex, are depicted in figures 1

and 2, and the methodology used is also described.

INTRODUCTION

Nowadays, men have reached an unusual development. Tools, equipment, machines and all kind of

technology that are available aim for comfort and well-being in our daily life, as well as effectiveness,

adaptability, prevention and for safety at work. These advances always arrive of the hand with new models

of equipment, machines, tools or vehicles, which more dissimilar, force men to adapt themselves inside of

or outside of them, implying possible risks, mainly at work places (McCormick, 1982).

In all men’s activities, some or a lot of physical effort is needed, and they need and will continue needing

physical assistance to reduce fatigue, to improve manufactured items or to produce them more quickly;

some examples are: pincers or a hammer in a shop, a typewriter in an office, a pan in the kitchen or a

stairway and its handrails in a building, etc.

New scientific approaches and technological advances are key elements in designing to achieve higher

productivity with almost perfect equipment and machinery. These items should eliminate the sources of

risks and injuries. Designs should also take into account men’s physical characteristics, limitations and

capabilities who will use them; designs must adapt physical tools to users and should avoid unnecessary

efforts, tasks must be performed quickly, easily and safely, since individuals are more productive being

comfortable at work.



Adapting tools to users or workers should not only be bounded to the operator, but to all persons that will

work with them, such it is the case of the maintenance personnel. Any internal part of equipment or

machine should be accessible and be able to provide the necessary space to make any repair (Flores,

2001).

Mexican workers also have to adapt themselves to working tools and conditions, mainly for three

circumstances: there is a great quantity of equipment and machinery that were bought in foreign countries,

which were not designed to be operated by the Mexican population; Mexican manufacturers produce their

items erroneously, they design them as they were designed in other countries and the most dramatic

situation is that they don't know the physical characteristics (anthropometric data) of the Mexican

population, or perhaps they have not been published.

The Mexican anthropometric data found in the literature, up to now, have little information and they were

collected from certain regions.

a. The Yucatan population's anthropometric data is a research carried out by George Dee Williams in

1927 and published in 1931 by the Bureau of International Research of Harvard University and

Radcliffe College under the name of "Mayan-Spanish Crosses in Yucatan".

b. Anthropometric measurements of some selected world populations, were presented as a report by

Robert M. White during the International Symposium of Engineering of Human Factors in 1972. This

report presents the dimensions of the military Air Forces of eighteen (18) Latin American countries

on the whole, but the reference of the source of information is not shown.

c. Datos antropométricos de la población de Ciudad Juárez, is a study carried out in 1986 and 1987

by the Center of Graduates of the Technological Institute of Ciudad Juárez. This investigation

presents 50 anthropometric data of 987 adults, mainly from the maquiladora industry.

d. “Estudio de ergonomía estática en una empresa textil Mexicana” was published in the journal

Condiciones de Trabajo, in 1979.



e. Anthropometry of female maquila workers, is a research published in the International Journal of

Industrial Ergonomics in 1999 by Victor Liu, David Sanchez Monroy and Guillermo Parga. It

presents twelve body dimensions of women workers in the maquiladora industry.

f. Cartas antropométricas para la población laboral de la maquila de Ciudad Obregón, is a research

conducted by Claudia Elena Mungarro Ibarra, in 2009.

g. Cartas antropométricas de adultos con enanismo de 18 a 45 años de edad para el diseño de

mobiliario, this survey was carried out in Mexico City, by Rubén Baptista Balderas, an Industrial

Design graduate student at Centro Universitario UAEMéx Zumpango, who took body dimensions of

adults with dwarfism among 18 to 45 years old to design different furniture.

h. Cartas antropométricas de la población laboral del estado de Sonora, área serrana, this study

gathered body dimensions of workers in the northeastern region of the state of Sonora, Mexico and

it was performed by students of the Universidad de la Sierra in the state of Sonora in 2008.

i. Cartas antropométricas de la población laboral de la República Mexicana, a research published by

the Instituto Tecnológico of Hermosillo.

Some employers may perceive that since tasks are designed or redesigned, whatever the operator will

need may be, carefully, taken into account, but it may increase their investment, but in the long run,

investment will be recovered and the gains will be financially enlarged.

On the other hand, if an employee works comfortably when he/she is sitting down, he/she will not feel tired,

will not feel any pain, and will be able to work easily and relaxed, and his/hers items quality will increase,

as well as effectiveness and efficiency. In such scenario, health care costs will decrease and the

employee’s moral will improve.

Ergonomics principles can avoid injuries or painful illnesses that can handicap workers and make work

places more comfortably safe in productive environments (McCormick, 1982).

Anthropometric data`s main utilization is objects designed for human use, such as tools, furniture, work

stations, facilities, etc. which optimize working and living conditions.



As it can be seen, designing for human use is a wide objective, and to achieve good results it is necessary

to keep in mind that who is or will be a product’s customer. That is the main reason that anthropometric

data is necessary as another tool for work designers, and its gathering takes time and it is quite expensive.

OBJECTIVES

To gather anthropometric data of students of the University of Sonora, in Hermosillo, Sonora, México, for

different population strata, for:

a) Age range (3), and

b) Sex (2)

METHODOLOGY

A group of four trained people got the anthropometric data of 227 students. Three of the investigators (M.

E. P. B. and A. M. M.) trained this group; they covered techniques, devices to use; and the required

theoretical and practical knowledge to carry out the necessary activities.

The trained group carried out the project with students of the University of Sonora in Hermosillo, Sonora,

México. Students were asked to wear light clothing and to take off their shoes during the study.

An anthropometer, a graduated scale in kilograms, and a survey of anthropometric data to register

measurements were used.

Measurements were taken by the students’ right side posture, when they were standing straight up, and

also sitting down, in an erect position.

1. Standing straight up. The individual remains standing straight, seeing toward the front, with the

ankles together, the weight distributed equally in both feet and with his arms hanging naturally to his

sides.

2. Sitting down straight. The individual remains sitting down and straight, with his/her view toward the

front, the arms relaxed and hanging, forearms and hands extended forward, thighs were horizontal,

and his/her feet resting in an adjusted surface so that the knees were in an angle of 90 degrees.



Data were gathered and processed in Excel software, and percentiles were later determined.

Data were grouped by sex, age and geographical regions, in the following way:

a. for sex: women and men,

b. for age, from 17 to 20, from 21 to 23 and from 24 years old and up.

c. Birthplace, the Mexican Republic was divided by several areas:

North zone, for the States of Chihuahua, Coahuila, Durango, New León and Zacatecas.

Centered area that includes the States of Aguascalientes, Mexico, Guanajuato, Hidalgo, Morelos, Puebla,

Querétaro, San Luis Potosí', besides Mexico Federal District.

Northern Pacific area: The states of the Northwestern area such as Sonora, Baja California, Sinaloa and

Nayarit.

Center Pacific area, for the states of Jalisco, Michoacán and Colima.

South Pacific area: for the states of Guerrero, Oaxaca and Chiapas.

Gulf of Mexico area, includes the states of Tamaulipas and Veracruz.

The different areas were settled down, arbitrarily, following the approach of their geographical proximity.

In figures 1 and 2, are shown the codes used, their description and the individual's position. This code was

taken from a study carried out by the NASA.



UNIVERSIDAD DE SONORA. Carta Antropométrica

Edad: 15-20 21-30 31-40 41-50 51-60 Sexo: F M Lugar de Nacimiento (Estado): _______________________________________ Ocupación: ____________________________________ Lugar de Nacimiento (Estado): Padre: _____________________________ Madre: ______________________________________ Analista: _________________________________________________________ (Usar ropa ligera y ajustada al cuerpo)

920 Peso (Kg) 122 Ancho de hombros

805 Estatura 223 Ancho de pecho

328 Altura al ojo 457 Ancho de cadera (parado)

23 Altura al hombro 32 Largo de brazo

309 Altura al codo 67 Profundidad del pecho

949 Altura a la cintura (ombligo) 430 Circunferencia de la cabeza

398 Altura al glúteo 639 Circunferencia del cuello

973 Altura a la muñeca 230 Circunferencia del pecho

66 Altura a los nudillos 931 Circunferencia de la cintura

265 Altura al dedo medio 68 Circunferencia del brazo

797 Ancho de brazos extendidos lateralmente

178 Circunferencia de la cadera

798 Ancho de codos con las manos al centro del pecho

69 Circunferencia de la pantorrilla

80 Distancia de la pared al dedo medio 144 Distancia de oído a oído sobre la cabeza



Elaboró: GF y SM Figure 1. Codes used, their description, and the individual's position.

427 Ancho de la cabeza 912 Altura del asiento a los nudillos con los brazos extendidos hacia arriba

595 Altura de la barbilla a la parte superior de la cabeza

200 Longitud desde el respaldo del asiento a la parte posterior de la rodilla

441 Longitud de la cabeza 194 Longitud desde el respaldo del asiento al frente de la rodilla

420 Longitud de la mano 2fgm Altura desde el suelo a la cabeza (sentado)

656 Longitud de la palma de la mano 4fgm Altura desde el suelo al asiento

411 Ancho de la palma de la mano 529 Altura desde el suelo a la rodilla (sentado)

859 Ancho de muslos con las rodillas juntas (sentado)

678 Altura desde el suelo a la parte posterior de la rodilla (sentado)

758 Altura del asiento a la cabeza 70 Longitud desde el codo al dedo medio

330 Altura del asiento al ojo 507 Ancho de la espalda con los brazos extendidos hacia el frente

25 Altura del asiento al hombro 459 Ancho de la cadera (sentado)

752 Distancia de la pared al nudillo 165 Ancho de la cara a la altura de las patillas



312 Altura del asiento al codo a 90° 775 Longitud del pie

856 Altura al muslo 776 Alto del pie

914 Altura del asiento al dedo medio con brazos extendidos hacia arriba

777 Ancho del pie

Elaboró: GF y SM Figure 2. Codes used, their description, and the individual's position.



RESULTS

Six anthropometric data were obtained from a sample of 227 students, for women and men, for three group

of ages from 17 to 20, from 21 to 23 and from 24 to 54 years old.

Hereby are presented two anthropometric surveys where body dimensions are described, measurements are

in centimeters and weight is shown in kilograms for 5th, 50th and 95th percentiles of a women’s sample

(figure 3) and for a masculine sample (figure 4), both, from 17 to 20 years old. In figure 5 data shows a

sample size of 227 masculine and feminine students by age range and sex.

Measurement’s Desription 5% 50% 95% Measurement’s Description 5% 50% 95%

Weight 37.17 66.6 96.02 Length of head 17.042 19.241 21.441 Stature 151.77 165.54 179.3 Length of hand 15.828 17.594 19.36

Length of palm of hand 7.831 9.8366 11.842 Height standing Width of palm of hand 4.5519 7.8598 11.168 Eye 139.97 153.73 167.5 Diameter of grabs (interior) 36.064 45.146 54.228 Shoulder 123.24 136.02 148.8Elbow 86.196 107.4 128.6 Heights sitting Waist 91.871 101.94 112 Height to head from seat 71.443 85.524 99.605 Buttock 65.34 74.432 83.52 Height to eye from seat 67.182 75.012 82.842

Wrist 53.194 82.124 111.1Height to shoulder from seat 50.45 59.456 68.462

Middle finger 54.842 63.695 72.55Height to elbow from seat, 90 degrees 20.364 24.951 29.538

Width of extended arms 151.27 166.63 182 Height to thigh from seat 10.891 14.046 17.202 Width of elbows to the center of chest 70.412 85.588 100.8

Height to Middle finger from seat, arms up 117.5 129.26 141.01

Length of arm extended from the wall 64.072 81.687 99.3

Height to center of fist, arms up 100.41 122.3 144.2

Length to the center of the fist from the wall 51.492 73.712 95.93

Height to head from floor sitting 121.12 131.11 141.1

Width of shoulders standing 34.828 42.038 49.25Hight to seat from floor sitting 23.215 49.154 75.092

Width of chest standing 24.719 30.34 35.96 Popliteal to buttocks 39.537 47.641 55.746

Width of hips standing 26.245 33.701 41.16Length from knees to buttocks 48.308 59.027 69.745

Circumferencia of neck standing 23.618 35.539 47.46 Height from floor to popliteal 35.818 43.388 50.958 Circumferencia fo chest standing 73.352 90.66 108 Height from floor to knee 40.054 52.266 64.477 Circumferencia of waist standing 55.12 79.619 104.1

Length from elbow to middle finger 40.634 44.907 49.18

Circumference of hips standing 81.893 99.361 116.8

Width of back with arms extended forward –forward reach 34.85 40.587 46.323

Circumference of head 46.695 54.395 62.1 Width of hips, sitting 32.447 38.468 44.489 Distance from ear to ear over head 26.672 34.971 43.27

Width of thighs with knees meeting 30.701 37.212 43.723

Width of face to the height of sideburns 11.977 13.563 15.15 Length of foot 21.381 24.137 26.892 Width of head 13.645 14.973 16.3 Width of foot 6.4972 8.4366 10.376 Height of chin to superior part of head 18.517 22.146 25.78 Height of instep 4.3354 6.2829 8.2305

Figure 3. Body dimensions for a femenine sample from 17 to 20 years old.



Measurement’s description 5% 50% 95% Measurement’s description 5% 50% 95%

Weight 42.488 71.49375 100.49 Length of head 16.075 19.574 23.073Stature 159.93 171.5791 183.23 Length of hand 15.673 18.054 20.435

Length of palm of hand 8.6763 10.373 12.07Height standing Width of palm of hand 6.6558 8.1094 9.5629Eye 146.22 158.5875 170.955 Diameter of grabs (interior) 41.309 47.465 53.621Shoulder 130.06 141.2395 152.41Elbow 92.509 109.3958 126.28 Heights sitting Waist 95.292 105.0958 114.9 Height to head from seat 68.123 86.91 105.7Buttock 54.349 79.39791 104.44 Height to eye from seat 67.85 77.194 86.538Wrist 59.077 85.08333 111.08 Height to shoulder from seat 51.535 61.767 71.998

Middle finger 57.349 65.675 74.000Height to elbow from seat, 90 degrees 20.315 25.654 30.993

Width of extended arms 160.06 173.7833 187.50 Height to thigh from seat 11.199 14.198 17.196Width of elbows to the center of chest 80.408 88.92812 97.448

Height to Middle finger from seat, arms up 123.05 135.74 148.43

Length of arm extended from the wall 74.883 84.65416 94.425

Height to center of fist, arms up 113.39 126.16 138.93

Length to the center of the fist from the wall 65.872 74.74166 83.6111

Height to head from floor sitting 122.9 132.74 142.57

Width of shoulders standing 35.141 44.8 54.458Hight to seat from floor sitting 25.36 49.129 72.899

Width of chest standing 26.262 31.33333 36.4043 Popliteal to buttocks 41.01 48.425 55.84

Width of hips standing 29.324 35.1 40.876Length from knees to buttocks 51.866 59.494 67.121

Circumferencia of neck standing 18.107 38.59791 59.088 Height from floor to popliteal 37.174 43.798 50.422Circumferencia fo chest standing 75.157 92.11041 109.06 Height from floor to knee 45.236 52.631 60.026Circumferencia of waist standing 62.925 84.41458 105.90

Length from elbow to middle finger 40.184 46.278 52.372

Circumference of hips standing 81.922 97.05833 112.19

Width of back with arms extended forward –forward reach 38.252 43.581 48.911

Circumference of head 46.276 56.28666 66.297 Width of hips, sitting 31.955 38.346 44.737Distance from ear to ear over head 25.215 35.57708 45.939

Width of thighs with knees meeting 29.586 36.777 43.969

Width of face to the height of sideburns 12.364 14.04375 15.723 Length of foot 22.467 25.502 28.537Width of head 13.581 15.52604 17.471 Width of foot 6.2461 8.6625 11.079Height of chin to superior part of head 19.43 22.74375 26.057 Height of instep 4.812 6.5781 8.3443

Figure 4. Body dimensions of a masculine sample from 17 to 20 years old.



Estratum by age

Masculine

Feminine

17-20

48

41

21-23

85

47

24-54

3

3

TOTALS

136

91

Figure 5. Sample size, grouped by age and sex of students of the Universidad de Sonora.

CONCLUSIONS AND SUGGESTIONS

Ergonomics emerged exclusively to increase worker's productivity, with time, it has become into a

multidiscipline, it looks forward to make tools more functional and spaces habitable, to improve aspects like

the men’s safe, comfort and health.

At present times, muscular – skeletal problems are often found in workers, "in such situations applied

Ergonomics is useful because it improves adaptability of physical persons’ limitations to environmental

conditions and to work tools, avoiding the development of pathologies like tendinitis, cervical and lumbar

injuries, among others."

Products, tools, machines, work places and furniture should be designed thinking of the activity or activities

that people will carry out on them. A work place can have more than one worker and its design should be

adjustable, that is why sometimes, it is necessary to build products of several sizes in such a way that

someone would have the possibility to choose the one that better adapts to the user's necessities, the other

one, would be to create products that are adjustable in a certain range of body dimensions, making necessary

to know the benefits and costs in such a way that decisions that are taken are the correct ones.



As it can be seen, everything that is manufactured, elaborated to interrelate with man should use their

dimensions, it is necessary to know human anthropometry.

The anthropometric data gathered in this research is one more effort added to those that were made

previously in Mexico. Body dimensions of students of the University of Sonora, in Hermosillo, Sonora,

Mexico includes male and female from 17 to 20, 21 and from 23 to 24 years old and older students; natives

and non natives from Hermosillo. These sample is build of 60.87% men and 39.83% women, 100% belong

to the North Pacific area and 93.52% were born in the state of Sonora.

Suggestions that can be made are: to invite researchers, education institutions and companies to develop

anthropometric data of Mexican populations, aiming to design production systems that will fulfill their main

goals: to increase productivity and to produce high product quality, optimizing workers’ safe and comfort at

the same time, so that they would allow them to compete in today’s global business.

REFERENCES

1. McCormick, Ernest and Sanders, Mark. (1982). Human Factors in Engineering and Design. United States of America. McGraw-Hill Book Company.

2. Neufert, Ernest. (1977). The Art of Projecting in Architecture. Barcelona, Spain. Editorial Gustavo Gil, S. A.

3. Instituto Mexicano del Seguro Social (1982). Lecturas en materia de seguridad social. Ergonomía. México.

4. Flores, Cecilia. (2001). Ergonomía para el diseño. Designio.

5. Mondelo, Gregori, de Pedro Gómez. (2002). Ergonomía 4. El trabajo en oficinas. Editotial Alfaomega.

6. Murrell, K. F. H. (1979). Ergonomics. London, England. Chapman & Hall.

7. Konz, Stephan. (2004) Work Design. Columbus, Unites States. Grid Publishing.

8. Unites States of America. NASA. (1987). Anthropometric Source Book, Vol 2: A Handbook of Anthropometric Dates.



ANTHROPOMETRY AND FACILITIES DESIGN VERIFICATION OF NEW DEVELOPED PRESCHOOL LEVEL BUILDINGS IN THE EDUCATIONAL SECTOR OF HERMOSILLO, SONORA.

Hiram Jesús Higuera Valenzuela1, Manuel Sandoval Delgado1

1Departamento de Investigación y Posgrado

Instituto Tecnológico de Hermosillo Ave. Tecnológico S/N Colonia Sahuaro

Hermosillo, Sonora 83170

Corresponding author’s e-mail: [email protected], [email protected] Resumen: Esta investigación nace de la problemática de la no existencia de tablas antropométricas de la población infantil principalmente en la edad de preescolar en México, las utilizadas por el Instituto Nacional de la Infraestructura Física Nacional no incluyen datos pertenecientes a infantes en edad de preescolar, las cuales se utilizan para la elaboración de mobiliario y dimensionamiento en el diseño de las instalaciones educativas (INIFED). Antropometría infantil. Abstract: This research comes from the lack of anthropometric charts for Mexican children in pre-school level, the charts used by the Instituto Nacional de la Infraestructura Física Nacional (National Institute for Educational Facilities) do not include data from pre-school level children; those charts are used to build furnishing and to determine the right size of the facilities (INIFED). Children’s Anthropometry

1. INTRODUCTION

Current situation in developing countries and economic growth, lack of in-house technologies and economic and technological dependence favor the use of models designed by other cultures (Oborne, 2007).

2. OBJETIVES

Check if design is within measurements found in the anthropometry charts in new pre-school level buildings in Hermosillo, Sonora during 2007 and 2008, since previously built schools show a lot of mistakes regarding the facilities’ size and the furnishing causing a lot of discontents and troubles in teachers and family parents in pre-school level buildings.

3. METHODOLOGY



3.1 Programming stage

a) The aim of this anthropometric research must be very clear, specifying if data collected will be used for a new design, redesign or to create a general purpose database.

b) It is necessary to define the kind of anthropometric technique that will be applied, which can be “Static Anthropometry” or “Dynamic Anthropometry”. (Flores G., 1997).

Static anthropometry measures the body still. It measures the skeleton between specific anatomic points. Dynamic or functional anthropometry it’s the one which measures the body in motion, acknowledging that the actual reach of a person’s arm it’s not equal to the length of the arm itself, but it takes into consideration the additional reach provided by the movement of the shoulder and torso when a person is working (Ergocupacional).

c) Once that the kind of anthropometric technique has been chosen, all the measures that will be used need to be specified and for this we need to keep in mind our final goal. In order to choose the measures we need to take, we must refer to the general anthropometric set (static or dynamic), taking into account the name and standard reference points in order to keep the techniques systematization.

d) Once that the measures to be taken have been defined, the anthropometric chart to be used needs to be designed. A copy of the chart for each subject needs to be built.

e) Besides the good quality and accuracy of the measuring equipment, portability it’s important, since most of the time it will be necessary to go where people who will be measured is. The most basic equipment must include anthropometric chart, portable anthropometer, flexometer, and tape measure. (Flores G., 1997).

Figure 1. Anthropometric chart and portable anthropometer.

3.2 Sampling

In this stage it’s when individuals in new facilities start to be measured in order to collect raw data; this is 32 measures by each individual.

3.3 Statistics Analysis

Once that the data is collected, it is analyzed and an anthropometric chart is built; percentiles 95, 50, 5 come from this chart, those are used to build facilities and furnishing.



The impossibility to make a design for the whole population forces us to pick a segment which includes the data in between. Thus, highest and lowest values are left out and focus on the 90% of the population. As a norm, the practical totality of anthropometric data is expressed in percentiles. In order to make this research more effective, population is broken into percentages categories, sorted from lowest to highest according to a specific body measure. For example, the first height percentile indicates that 99% of the individuals measured would be above this dimension. In the same way, a percentile of 95% in height would state that only 5% of the individuals measured would be over it, since the remaining 95% would be just as tall or shorter. (Panero, 1993).

3.4 Steps to get percentiles

1. Summation of raw data is calculated In a spreadsheet (total of measures), mean or average is calculated using the following formula:

(1)

� = Data mean or average ΣX = Summation of the values of all the measures. n = Number of elements of the sample. 2. Standard deviation it’s calculated, which defines the individual deviation of each

measure regarding to the mean. 2 3

s2 = Variation of the sample. s = Standard variation of the sample. x = Value of the measures. � = Mean of the sample. n - 1 = Number of measures of the sample -1 3. Standard deviation of the unit it’s calculated, which is called “z”, where z equals to:

(4)

x = Random variable value � = Average distribution of the random variable. s = Standard variation of this distribution. z = Number of standard deviations of x regarding the mean of this distribution. (Navidi, 2006).



4. Percentiles are calculated 5 6 7

(8)

(DINBelg)

4. RESULTS

Since this is an ongoing research, some of the necessary measures are still missing in order to conduct a full test of the facilities and furnishing, however, there is an anthropometric chart with the data collected so far and it is possible to get preliminary results in order to get the dimensions for facilities and furnishing.

In this example the dimensions of the sink and classroom chairs will be used. In order to calculate height and width for the sink measures 949 (height to the waist) and 752 (distance from the wall to the center of the fist) Results for 949 X = 61.55 S = 4.88 5 % = 61.55 – (4.88 x 1.65) = 53.498 cm (9) Results for 752 X = 46.26 S = 3.66 5 % = 46.26 – (3.66 x 1.65) = 40.221 cm (10)



Figure 2. Sink dimensions

In order for most of the children to be able to use the sink without any problems percentile 5 from mean 949 and 752 was used.

Measures 200 (length from the back of the knee to the back of the chair), 678 (height from the ground to the back side of the knee), 459 (width of hips, sitting down), 25 (height from the seat to the shoulder) are used in order to get the dimensions of the chair. Results for 200 X = 28.82 S = 2.13 5 % = 28.82 – (2.13 x 1.65) = 25.3055 cm (11) Results for 678 X = 28.98 S = 2.38 5 % = 28.98 – (2.38 x 1.65) = 25.053 cm (12) Results for 459 X = 22.09 S = 1.95 5 % = 22.09 + (1.95 x 1.65) = 25.3075 cm (13) Results for 25 X = 37.56 S = 2.54 5 % = 37.56 – (2.54 x 1.65) = 33.369 cm (14)



Figure 3. Chair dimensions

5. CONCLUSIONS

This research is extremely important since there are no anthropometric charts for pre-school level children in Mexico. These charts are used to build furnishing and determine the size of new schools buildings. This project aims to get the necessary information in order to build these charts.

6. REFERENCES

Flores G., Cecilia (1997) Antropometría Aplicada, Primer Encuentro Internacional de Ergonomía, Instituto Tecnológico de Mérida, Mérida Yucatán.

Oborne, David J. (1990 reimpresión 2001), Ergonomía en acción la adaptación del medio de trabajo al hombre. – 2ª edición – México: Trillas.

INIFED (Instituto Nacional de la Infraestructura Física Educativa 2008), Normas y Especificaciones para Estudios, Proyectos, Construcción e Instalaciones, Volumen 3 Habitabilidad y Funcionamiento, Tomo III Diseño de Mobiliario. http://www.inifed.gob.mx/templates/normas%20t%C3%A9cnicas.asp (Visited on May 15, 2009).

ERGOCUPACIONAL Uso de tablas antropométricas en ergonomía, http://www.ergocupacional.com/4910/35922.html (Visited on March 8, 2010).

Panero Julios (1993) Las dimensiones humanas en los espacios interiores. Ed. G. Gili, S.A. México, D.F.

Navidi William (2006) Estadística para ingenieros y científicos. McGraw-Hill Interamericana. México, D.F.

DINBelg Body dimensions of the Belgian population Formulas, http://www.dinbelg.be/formulas.htm (Visited on March 8, 2010).



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DESIGN ANTHROPOMETRIC REFERENCED LETTERS TO THE LABOR POPULATION OF CABORCA CITY IN SONORA MEXICO.

M.C. Joaquín Vásquez Quiroga1, M.C. Jesús Rodolfo Guzmán Hernández2, Dr. Enrique Javier de

la Vega Bustillos3.

Program Coordinator and Professor, Department of Physics, Mathematics and Engineering, Universidad de Sonora, Caborca Sonora, México.

[email protected]

Professor and Researcher at the Instituto Tecnológico de Hermosillo, Mexico [email protected]

Professor, Department of Physics, Mathematics and Engineering

Universidad de Sonora, Caborca, Sonora, México. [email protected]

RESUMEN Esta investigación es el resultado de las mediciones de 50 variables antropométricas de 200 personas en edad laboral de la Ciudad de Caborca Sonoro México, con el objetivo de poder hacer una aportación importante a la creación de cartas antropométricas para la población mexicana. En la actualidad son pocos los datos que se tienen de las medidas antropométricas de la población mexicana, haciéndose necesario utilizar las medidas de otros países en donde las condiciones y complexión física son diferentes. Las cartas antropométricas que aquí se obtuvieron están distribuidas por grupos de edad, sexo y lugar de origen. Este trabajo puede ser el inicio de investigaciones similares en otras poblaciones de México y llegar a tener un registro antropométrico del total de la población mexicana, para poder desarrollar estaciones o espacios de trabajo que se adapten a la población, herramientas, ropa, equipo de protección personal como cascos y guantes, calzado, lo mismo que lugares de descanso. Palabras claves: Cartas Antropométricas, Antropometría y Ergonomía. ABSTRACT This research is the result of 50 anthropometric measurements of 200 people of working age of Caborca Sonora Mexico City, in order to be able to make a significant contribution to creating cards for the Mexican population anthropometric. At present there are few data have anthropometric measurements of the Mexican population, making it necessary to use measures other countries where conditions and physique are different. The anthropometric letters were obtained here are divided by age, sex and place of origin. This work may be the beginning of similar investigations in other populations of Mexico and get to have a record of all anthropometric Mexican population, to develop stations or workspaces that are tailored to the people, tools, clothing, protective equipment personal as helmets and gloves, footwear, as well as resting places. Keywords: Anthropometric Letters, Anthropometry and Ergonomics.



1. INTRODUCTION It is now of vital importance to take into account the design and the anatomic structure of individuals to understand and develop all those areas in which performance involves human beings, this is not new and has been studied before in different countries and not with measures aimed at the Mexicans. The purpose of a study of this type is able to physically help the worker in all areas where it is involved, such as designing work spaces suitable for each person, the design of tools, safety equipment and personal protection clothing, and have references dimensional population. With all the technological advances that have occurred, you can have a better life, as studies have been developed in several areas, one of them is the anthropometry, with which they determine the dimensions of the human body, in this area there are some studies in developed countries, but very few of the Mexican population. Hence the interest start recording anthropometric data, thinking about making a contribution to the creation of anthropometric cards to this population. The creation of these cards is essential to have a population register, in order to make designs of stations, the design of tools and equipment, etc.., Always trying the user is comfortable and without risk of injury by position not normal. This is important to understand their measurement and to determine the field of development or dimensional capabilities that people have. For this reason the study will focus to working anthropometric cards of population of H. Caborca, Sonora, and this is an important input to record anthropometric measurements of the Mexican population. Throughout history, many investigations that have been developed in the area of anthropometry. In more current times these investigations have risen to be an important support for ergonomics, this is the case: Annis (1996) did an analysis of anthropometric changes the size and body shapes as they get older people, to see the implications of these changes in the dimensions of workspaces. Gosseens (1998) studied the dimensions of the seats of five different types of civil aircraft. The results were compared with existing standards and biomechanical criteria. It was evident that these seats failed to meet requirements of depth, slope, height of lumbar support and armrests. Therefore, none of these seats allow the pilot was in a comfortable sitting posture. In comparison with aviation standards, the anthropometric dimensions were not satisfactory.

Panagiotopoulou (2003) developed a study for the purpose of comparing the size of primary school students, with the dimensions of the desks, to determine if the dimensions of the furniture is well designed and see if they promote good posture sitting considering the dimensions of children.

Jung (2005) developed a prototype of an adjustable chair for educational institutions, where they assess their suitability according to international standards. His research began with simple mechanisms for adjusting the height of chair legs and backrest height and seat depth.

In Mexico, these investigations have increased due to the recommendations made in the Federal Regulation on Safety, Hygiene and Environment Working in Article 102 and as SEMAC associations (Society of ergonomic Mexicana AC), which organizes conferences in presented research papers such as:

Ergonomic design for computer work stations, presented by Martinez (2000). Implementation of an ergonomic process for the industry for control musculoskeletal

injuries, presented by Sánchez (2002). Research and Ergonomics in Mexico, presented by de la Vega (2004).



In developing this work is clearly important that represents the human resources within an organization, since this depends on the effectiveness of the production process. Therefore, the objective of the development of this research is the creation of letters of the anthropometric measurements of the working population of the City of Caborca, by age group, sex and place of origin.

Obtaining anthropometric cards may be made designs for the population, helping businesses and people in general. Currently there are very few reliable records of the anthropometric dimensions of these people, so it is taken as the measures of other countries where physique is different and the conditions too.

When designing industrial products is important to provide who are the users to succeed in the product, taking into account different body sizes, safety and human comfort, it is here that involves anthropometry (Reeder 2003).

Hence the great importance of anthropometric data to researchers from the human factor, for practical use with these, such as would be the design of clothing, tools, to provide statistical guidelines for product design and build models biomechanical. (Park, Kim 1997).

According Cavassa (2004) there are two types of anthropometrics: anthropometry static or structural, which refers to the dimensions in which the body is in static state, for example, height, weight, etc.

The other type is the dynamic anthropometry: it refers to taking action where the body is operating, for example stretching one arm to reach something.

At the time of wanting to design, there are some factors that influence the anatomical structure of the human body are: age (until maturity), sex (male, female), race, occupation, clothing (especially in cold weather ) and even the time of day (in the morning the people are measuring 6 mm more, because the spinal discs are not compressed (Konz 1999).

When will develop designs for a group of people is important to take into account some principles such as: 1. Design principle to extremes: this design takes the maximum and minimum value of the characteristics of user populations. 2. Adjustable design principle: it is used for facilities and equipment that can be adapted to various individuals. 3. Design principle for the average: this approach is less expensive but less used, since it is difficult to get the design that fits 50% of the population (Niebel 2001)

The anthropometric cards is to develop a record of human body stockings for people to have a higher confidence level to develop a design such as a workstation, machinery, equipment, clothing, etc. such is the case study by Mohammad (2005) which record some measures of hand. There are an infinite number of steps you can take the human body as recommended by the manual of procedures (Secretariat 2002). For the case study of this work, selected 50 of them, according to the definitions used in similar anthropometric examinations conducted by the National Aeronautics and Space Administration (NASA 1978).

2. MATERIALS AND METHODS

For the development of the research team used the following:

• three anthropometer model 01140, 01290 and 01291 marks Lafayette. • One stadimeter marks Seca. • One analog scale marks Seca.



• Two measuring tape marks Powerlock Stanley. • Two flexible tapes. • Two calibrators marks Chicago Brand. • Two chairs designed with a height adjustment system. • One calibrated cone diameter grip. • One computer for recording information. The methodology for taking the measures was as follows: It had a special area for training and standardization process of the four assistants in order to

achieve uniformity in the way of measuring. The measurements were conducted in a private room and quiet, being present only the

individual, the analyst and an assistant. People who were measured were treated with respect and care, trying to earn their trust. Before the measurement was given a brief explanation of the steps, procedures and

requirements for measurement. Was prepared and calibrated all equipment necessary to make anthropometric measurements,

ensuring that all necessary materials are available. To begin with the taking of measures, the person must wear few clothes, nothing in the head

or feet, the surface of the floor, seat or platform must be flat, horizontal and non-compressible, measure the right side of the person. At the time of the measures breathing should be light.

The 50 measures that were recorded for each person are:

Code Name of the measure N920 Weight N805 Stature N328 Standing eye height to N23 Standing shoulder height N309 The standing elbow height N949 Standing waist height N398 Height standing gluteus N973 Standing tall on the wrist N265 Standing height to the middle finger N797 Width arms outstretched N798 Width at center chest elbows N80 Arm length from the wall N752 Distance from wall to the center of the fistN122 Standing shoulder width N223 Standing chest width N457 Standing Hip Width N639 Standing neck circumference N230 Standing chest circumference N931 Waist circumference stands N178 Standing hip circumference N430 Head circumference N144 Distance from ear to ear on the head N165 Face width to the height of the pins N427 Head width N595 Height of the chin to the top of head N441 Head length N420 Length of hand



N656 Length of the palm N411 Width of palm N402 Grip diameter N758 Seat height sitting at the head N330 Seat height sitting in the eye N25 Seat height sitting shoulder N312 Seat height to seated elbow to 90 N856 Sitting thigh-high N914 Seat height to the middle finger sitting N912 Height to the center of the cuff arms up N2FGM Height of sitting down N4FGM Seat height from floor to sit N200 Back of the knee to the back of chair N194 Length from knee to back of chair N678 Height from floor to knee back N529 Height from floor to knee N381 Length from elbow to middle finger N507 Back Width arms outstretched in front N459 Seated hip width N859 Width thighs with knees together N775 Leg length N777 Foot width N776 High instep

Was measured at 200 and will be an analysis of data from the 200 people using the

spreadsheet Excel, the result will reflect the percentiles 5%, 50% and 95%, the maximum and minimum of each measurements.

3. ANALYSIS OF RESULTS

The results of research carried out in each of the measurements are shown in the tables or charts anthropometric working population of Caborca, Sonora, as follows:

Table 1 shows the total data by age group and sex in years, in tables 2, 3, 4, 5, 6, 7 and 8 shows the results of the analysis of the 50 measures anthropometric research by age, sex and place of origin.

The tables show the calculation of the percentiles 5, 50 and 95%, and the maximum and minimum measurements. The calculations were analyzed in the Excel spreadsheet. The weight calculation is given in kilograms, the other measures are in centimeters.

Table 1 Distribution of data by age group and sex.

AGE

SEX TOTALSMEN WOMEN

18-20 69 24 93 21-23 49 26 75 24-27 24 8 32

TOTALS 142 58 200



Table 2 Results of analysis of measures for the age ranges of 18-20 years. Percentile

Code Name of the measure 5% 50% 95% MIN MAX N920 Weight 48.6 68 93.4 40 105N805 Stature 156.8 170.5 183.4 151.1 194N328 Standing eye height to 145.3 160.2 173.6 140.5 182.4N23 Standing shoulder height 130.6 142.8 153.3 126 167.5N309 The standing elbow height 98.8 108.2 117.3 95.6 129.2N949 Standing waist height 93.6 102.5 110.4 92 121.7N398 Height standing gluteus 68.1 74 86.1 62 96.4N973 Standing tall on the wrist 75.4 83.6 90.3 71 105N265 Standing height to the middle finger 59.1 64.9 71.1 56 78.1N797 Width arms outstretched 156.6 175.1 187.2 150.7 200.7N798 Width at center chest elbows 79.3 91.5 97.2 68.3 99.4N80 Arm length from the wall 76.9 89.3 115 68.5 118N752 Distance from wall to the center of the fist 66.5 75.7 106.5 64.8 111N122 Standing shoulder width 37 43.3 48.1 34.5 54N223 Standing chest width 26.4 30.4 35 24.3 38.4N457 Standing Hip Width 31 35.4 39.8 30.3 46.7N639 Standing neck circumference 31.3 37 41.6 29.7 44N230 Standing chest circumference 81 94.5 110.2 77 117N931 Waist circumference stands 67.1 85 105.2 64.5 115.2N178 Standing hip circumference 90.3 102 117.9 84.7 127N430 Head circumference 54 57 60.5 52.5 98.4N144 Distance from ear to ear on the head 34.5 37 39.8 32.3 55N165 Face width to the height of the pins 12.9 14.4 15.7 11.7 15.9N427 Head width 14.5 15.5 16.9 12 17.9N595 Height of the chin to the top of head 20 23 25.2 18.5 25.7N441 Head length 17.5 19 20.3 16.4 20.9N420 Length of hand 16.4 18.5 19.8 16.1 21.2N656 Length of the palm 9.4 10.6 11.4 9.2 12.3N411 Width of palm 7.3 8.4 9.3 6.9 9.8N402 Grip diameter 4.2 4.8 5.6 3.5 6.5N758 Seat height sitting at the head 82 88.8 95.5 79 100.5N330 Seat height sitting in the eye 71.5 78 84.2 64.6 90.2N25 Seat height sitting shoulder 57 61.5 66.6 54.3 68.5N312 Seat height to seated elbow to 90 22 26 29 19.4 38N856 Sitting thigh-high 13.5 16 18.8 12 21N914 Seat height to the middle finger sitting 119.5 132.3 145.7 114 148.5N912 Height to the center of the cuff arms up 110.2 121.3 133.7 104.2 136.3N2FGM Height of sitting down 121.9 130 139.2 115.5 143.4N4FGM Seat height from floor to sit 37.8 42 45.6 36 47.2N200 Back of the knee to the back of chair 41 45.4 51 39.1 56.7N194 Length from knee to back of chair 53.2 59.2 66.5 48.4 72.3N678 Height from floor to knee back 37 42.3 45.4 33.5 49N529 Height from floor to knee 48.4 54.3 58.9 30.4 64.2N381 Length from elbow to middle finger 42.3 48 51.5 41.1 53N507 Back Width arms outstretched in front 37.2 42 46.9 32.7 49.9N459 Seated hip width 35.5 39.1 46.2 32 49.3N859 Width thighs with knees together 29.8 33.3 40 26.1 49.8



N775 Leg length 22.8 26 28.5 21.6 30.4N777 Foot width 8.6 9.7 10.7 8 11.2N776 High instep 6.2 8.3 10 5 12.3


Code Name of the measure 5% 50% 95% MIN MAX N920 Weight 51.7 68 106.3 47 132N805 Stature 153.5 168 181.3 148 184N328 Standing eye height to 142.2 157.5 169.8 138 174.2N23 Standing shoulder height 128 140.6 152 126 185.5N309 The standing elbow height 97 106.3 116.2 90.8 123.8N949 Standing waist height 93 100 111.3 91 116N398 Height standing gluteus 64.4 74 82.7 59 106.8N973 Standing tall on the wrist 73.6 82 92.2 69 95.3N265 Standing height to the middle finger 56.9 65 72.4 55 75.8N797 Width arms outstretched 153.7 172 186.3 152 189.6N798 Width at center chest elbows 77.9 89.2 95.6 64 98.2N80 Arm length from the wall 77.5 98 115.7 73.3 128.7N752 Distance from wall to the center of the fist 68 92 105.4 61.7 112N122 Standing shoulder width 37.4 42.8 48.3 35.5 51.1N223 Standing chest width 27.1 30.2 35.9 25.5 40N457 Standing Hip Width 32.4 35.7 43.2 30.5 45.2N639 Standing neck circumference 31 36.9 41.7 29.5 46N230 Standing chest circumference 85.9 96 118.2 83 124.5N931 Waist circumference stands 70 85 115.3 56 125.4N178 Standing hip circumference 93.9 104 125.7 91 135.5N430 Head circumference 54 56.8 59.2 53.5 61N144 Distance from ear to ear on the head 34 37 39.6 33.5 41N165 Face width to the height of the pins 12.9 14 15.8 12 16.7N427 Head width 14.1 15.5 16.5 12 16.8N595 Height of the chin to the top of head 19.5 22.2 24.8 19 25.8N441 Head length 17.4 18.9 20.5 17 24.6N420 Length of hand 16.4 18.1 19.7 15.6 20.5N656 Length of the palm 9.1 10.4 11.4 7.8 19.2N411 Width of palm 7.2 8.4 9.3 6.5 9.5N402 Grip diameter 4 4.7 5.4 3.4 5.6N758 Seat height sitting at the head 80.6 88 93.8 79 95N330 Seat height sitting in the eye 70.9 77.2 82.4 66.7 84N25 Seat height sitting shoulder 56 60.9 70.3 53.5 83N312 Seat height to seated elbow to 90 22 26 30.7 19.2 39N856 Sitting thigh-high 13.1 16 19.9 12 21.5N914 Seat height to the middle finger sitting 118.3 132.2 141 113.4 145N912 Height to the center of the cuff arms up 110 122.4 129.8 103.3 140.5N2FGM Height of sitting down 119 130 137 115.4 140N4FGM Seat height from floor to sit 37.3 41 45 36 46.5N200 Back of the knee to the back of chair 40.1 46 50.1 39.7 55N194 Length from knee to back of chair 52.7 59 64.4 51 70.5N678 Height from floor to knee back 36.6 42 46 35.5 50.9



N529 Height from floor to knee 47.3 54 58.6 43.4 65.5N381 Length from elbow to middle finger 40.9 46.6 51 40 54N507 Back Width arms outstretched in front 36.7 41.6 46.1 34 47.7N459 Seated hip width 35.5 39 46 29 54.7N859 Width thighs with knees together 30 33.5 40.2 28.4 46.8N775 Leg length 22.7 25.5 27.8 22 28.6N777 Foot width 8.4 9.8 11 8 12N776 High instep 5.9 8 9.2 5 10.5


Code Name of the measure 5% 50% 95% MIN MAX N920 Weight 57.6 74.5 108.4 50 138N805 Stature 158.9 171 183.3 156 187N328 Standing eye height to 147.3 161 169.7 132 177.6N23 Standing shoulder height 132 142.5 153.8 131 159.3N309 The standing elbow height 102.3 107.5 117.5 100.5 119N949 Standing waist height 91.3 101 109 85 113N398 Height standing gluteus 65 73 80.7 62 89N973 Standing tall on the wrist 76.1 81 92.2 68.5 92.8N265 Standing height to the middle finger 59.8 65.1 72.9 58.5 74N797 Width arms outstretched 160 174 188.2 155 193N798 Width at center chest elbows 85 91 96.3 83 99N80 Arm length from the wall 81.3 95.2 116.3 77 122.5N752 Distance from wall to the center of the fist 62.8 87.2 106.7 60 107N122 Standing shoulder width 38 44.7 49.5 36.2 52.9N223 Standing chest width 27.6 32 37.3 26.2 41.4N457 Standing Hip Width 31.6 36 44.2 31.5 76.5N639 Standing neck circumference 32.6 38 44 31 44.8N230 Standing chest circumference 86.6 98.4 117.5 85.5 150N931 Waist circumference stands 74.8 90 120 70 151.8N178 Standing hip circumference 94.6 107.2 122.9 93 149.5N430 Head circumference 54.8 57.5 60 54 60N144 Distance from ear to ear on the head 34.6 36.8 40 34 40N165 Face width to the height of the pins 12.5 14.1 16.1 11.4 16.2N427 Head width 14.4 15.3 16.7 12.4 17N595 Height of the chin to the top of head 20.9 23 27.1 20 29N441 Head length 17 19 20.2 16 20.6N420 Length of hand 17 18.6 20 17 20.1N656 Length of the palm 9.6 10.7 11.3 9.5 22N411 Width of palm 7.3 8.7 9.1 7 9.3N402 Grip diameter 4 4.9 5.6 3.8 5.8N758 Seat height sitting at the head 84.3 88.2 93.2 83 98N330 Seat height sitting in the eye 72.9 77.1 83 70 84.5N25 Seat height sitting shoulder 58 61 68.1 57 83N312 Seat height to seated elbow to 90 21.8 27.2 29.8 21 32N856 Sitting thigh-high 13.7 16.3 18.9 13 20N914 Seat height to the middle finger sitting 122.4 131.8 140.8 117.4 150N912 Height to the center of the cuff arms up 111.7 122 129.7 109.4 138



N2FGM Height of sitting down 123.6 130 137.8 121.5 139N4FGM Seat height from floor to sit 37.6 41.8 46.2 37 47N200 Back of the knee to the back of chair 41.4 45.3 49.1 40 53.5N194 Length from knee to back of chair 55.4 58.2 65 53 67.2N678 Height from floor to knee back 37.8 42.7 46.3 36 48.5N529 Height from floor to knee 50.4 55.3 61 49.5 63.2N381 Length from elbow to middle finger 43.6 47 49.5 41 50.3N507 Back Width arms outstretched in front 37.2 43 47.8 35 49.7N459 Seated hip width 36.3 39.5 48.4 36 56.4N859 Width thighs with knees together 29.3 34.6 43.8 27.5 52.6N775 Leg length 23.1 26 28.3 23 30N777 Foot width 9 9.7 11 8.7 11N776 High instep 6.1 8 10 6 10

Table 5 Results of analysis of measures for female. Percentile

Code Name of the measure 5% 50% 95% MIN MAX N920 Weight 46.9 57.5 95 40 138N805 Stature 151 160 172 148 172.8N328 Standing eye height to 140.9 149.4 159.7 138 161.6N23 Standing shoulder height 126.9 133 142.4 126 147N309 The standing elbow height 96.8 102.9 109.9 94 114N949 Standing waist height 92.6 98.5 106.5 85 109N398 Height standing gluteus 66.3 72.4 80.1 61.5 82.7N973 Standing tall on the wrist 73 79.4 85.8 71 87N265 Standing height to the middle finger 56.4 62.1 68.1 56 69.9N797 Width arms outstretched 152.4 160.4 176.5 150.7 177N798 Width at center chest elbows 73.9 83.5 89.6 64 93.7N80 Arm length from the wall 75.5 81.8 106.5 73.3 114N752 Distance from wall to the center of the fist 64.7 71.7 98.9 61.7 104.5N122 Standing shoulder width 35.5 39.6 46.6 34.5 52.9N223 Standing chest width 26 29 35.4 24.3 41.4N457 Standing Hip Width 32.6 35.6 45 30.3 46.7N639 Standing neck circumference 30 33 38.2 29.5 44.8N230 Standing chest circumference 82.8 92.5 118.5 79.8 150N931 Waist circumference stands 66 77.5 112.2 64.5 151.8N178 Standing hip circumference 92.7 99.2 127.2 84.7 149.5N430 Head circumference 53.5 56 58.2 53 98.4N144 Distance from ear to ear on the head 33.9 36 38.7 33 39N165 Face width to the height of the pins 12.3 13.5 15.1 11.4 15.8N427 Head width 14.2 15.1 16.2 12 17.9N595 Height of the chin to the top of head 19 22 24.2 18.5 29N441 Head length 17.1 18.5 20 16.4 20.3N420 Length of hand 16.1 17.5 18.9 15.6 19.4N656 Length of the palm 9 9.7 11.2 7.8 19.2N411 Width of palm 7 7.5 8.5 6.5 9.3N402 Grip diameter 3.9 4.5 5 3.5 5.6N758 Seat height sitting at the head 79.5 85 89.4 79 93N330 Seat height sitting in the eye 69.8 74.1 78.3 66.3 81.7



N25 Seat height sitting shoulder 55.8 59 63.5 53.5 69N312 Seat height to seated elbow to 90 22 26.6 29.6 20.5 39N856 Sitting thigh-high 12.6 15.2 18.7 12 21.5N914 Seat height to the middle finger sitting 114.9 123.7 133.1 113.4 135N912 Height to the center of the cuff arms up 108 115 122.5 103.3 127.7N2FGM Height of sitting down 117 124.8 131.1 115.4 134.1N4FGM Seat height from floor to sit 37 39.2 44 36 45.1N200 Back of the knee to the back of chair 40 44 49 39.1 49.2N194 Length from knee to back of chair 51 56.9 61.4 48.4 65.4N678 Height from floor to knee back 36 38.9 43.1 35.5 44N529 Height from floor to knee 46.6 51.1 55.3 30.4 56N381 Length from elbow to middle finger 40.7 44 47 40 49.1N507 Back Width arms outstretched in front 35.5 39.9 43.6 33 48.6N459 Seated hip width 35.1 39 49.2 32.7 56.4N859 Width thighs with knees together 30 33.7 42.8 28.5 52.6N775 Leg length 22 23.8 25.1 21.6 27.2N777 Foot width 8.1 9 10 8 10.3N776 High instep 6 7.7 9 5 9.7

Table 6 Results of analysis of measures for male.

Percentile

Code Name of the measure 5% 50% 95% MIN MAX N920 Weight 57.1 73 100.9 49 132N805 Stature 163 172 183.8 156.7 194N328 Standing eye height to 151 161.5 174 132 182.4N23 Standing shoulder height 135.2 144.2 153.5 132 185.5N309 The standing elbow height 102 109.7 118 90.8 129.2N949 Standing waist height 94.1 103 111.4 91 121.7N398 Height standing gluteus 65 74.7 88.6 59 106.8N973 Standing tall on the wrist 76 84 92.5 68.5 105N265 Standing height to the middle finger 59 66 73.4 55 78.1N797 Width arms outstretched 166 177.4 189.2 160.5 200.7N798 Width at center chest elbows 86.3 92.1 97.5 68.3 99.4N80 Arm length from the wall 84.2 93 116.6 68.5 128.7N752 Distance from wall to the center of the fist 72 79.8 107 60 112N122 Standing shoulder width 41 44.6 49.3 36.6 54N223 Standing chest width 28 31 36.4 25.7 40N457 Standing Hip Width 31.5 35.6 39.2 30.3 76.5N639 Standing neck circumference 34 37.9 42.5 32.8 46N230 Standing chest circumference 85.1 96.5 116.3 77 124.4N931 Waist circumference stands 73.1 87 111.4 56 126N178 Standing hip circumference 94 104 117.8 87 135.5N430 Head circumference 54 57 60 52.5 86.5N144 Distance from ear to ear on the head 34.5 37 40 32.3 55N165 Face width to the height of the pins 13 14.5 16 12.5 16.7N427 Head width 14.5 15.6 16.6 12.4 17.7N595 Height of the chin to the top of head 20.5 23 25.4 18.9 28.8N441 Head length 17.5 19 20.6 16 24.6N420 Length of hand 17.4 18.8 20 17 21.2N656 Length of the palm 10 10.7 11.4 9.5 22



N411 Width of palm 7.9 8.7 9.3 7.5 9.8N402 Grip diameter 4.1 4.9 5.6 3.4 6.5N758 Seat height sitting at the head 84 89.6 95.1 81 100.5N330 Seat height sitting in the eye 73 79 84 64.6 90.2N25 Seat height sitting shoulder 58 62 67.5 56 83N312 Seat height to seated elbow to 90 22 26 29.5 19.2 32N856 Sitting thigh-high 14 16.4 19.4 12.4 21N914 Seat height to the middle finger sitting 127.2 134.3 145 119 150N912 Height to the center of the cuff arms up 117 124 134 111.5 140.5N2FGM Height of sitting down 123.6 131.5 139 120.4 143.4N4FGM Seat height from floor to sit 38.5 42.3 46 36.5 47.2N200 Back of the knee to the back of chair 42 46 51.2 40 56.7N194 Length from knee to back of chair 55.7 60 66 52 72.3N678 Height from floor to knee back 39.2 43 46.7 33.5 50.9N529 Height from floor to knee 52.4 55.5 60.2 50.4 65.5N381 Length from elbow to middle finger 45 48 51.5 41.6 54N507 Back Width arms outstretched in front 38.4 43 47.2 32.7 49.9N459 Seated hip width 35.7 39.2 46 29 54.7N859 Width thighs with knees together 29.7 33.6 41.5 26.1 49.8N775 Leg length 24.7 26.4 28.6 24 30.4N777 Foot width 9 10 11 8.5 12N776 High instep 6 8.3 10 5 12.3

Table 7 Results of analysis of measures for Caborca people Percentile

Code Name of the measure 5% 50% 95% MIN MAX N920 Weight 50 69 100.9 40 138N805 Stature 155.1 169.1 183 148 194N328 Standing eye height to 143.3 158.4 173.2 132 182.4N23 Standing shoulder height 130.1 141.6 152.9 126 185.5N309 The standing elbow height 98 107.1 117.4 90.8 129.2N949 Standing waist height 93 101.5 110.5 85 121.7N398 Height standing gluteus 65.1 74 85.5 59 106.8N973 Standing tall on the wrist 75 82.5 92 68.5 105N265 Standing height to the middle finger 58 64.9 72.6 55 78.1N797 Width arms outstretched 155.1 174 187.6 150.7 200.7N798 Width at center chest elbows 79 90.2 97.3 64 99.4N80 Arm length from the wall 77.3 91.3 115.2 68.5 128.7N752 Distance from wall to the center of the fist 66.2 78.9 106.7 60 112N122 Standing shoulder width 37 43.2 48.5 34.5 54N223 Standing chest width 26.8 30.7 36.8 24.3 41.4N457 Standing Hip Width 31.6 35.6 42.5 30.3 76.5N639 Standing neck circumference 31 37 42 29.5 46N230 Standing chest circumference 84 95.9 117 77 150N931 Waist circumference stands 68.1 85.2 112 56 151.8N178 Standing hip circumference 93 103.3 121 84.7 149.5N430 Head circumference 54 57 60 52.5 98.4N144 Distance from ear to ear on the head 34 37 40 32.3 55N165 Face width to the height of the pins 12.9 14.2 15.9 11.4 16.7N427 Head width 14.5 15.4 16.6 12 17.9N595 Height of the chin to the top of head 19.6 22.8 25.4 18.5 29



N441 Head length 17.3 19 20.4 16 24.6N420 Length of hand 16.5 18.4 19.8 15.6 21.2N656 Length of the palm 9.3 10.5 11.4 7.8 22N411 Width of palm 7.2 8.5 9.3 6.5 9.8N402 Grip diameter 4 4.7 5.5 3.4 6.5N758 Seat height sitting at the head 82 88.3 95 79 100.5N330 Seat height sitting in the eye 71 77.4 83.7 64.6 90.2N25 Seat height sitting shoulder 56.8 61 67.3 54.3 83N312 Seat height to seated elbow to 90 22 26.3 29.5 19.2 39N856 Sitting thigh-high 13.1 16 19.4 12 21.5N914 Seat height to the middle finger sitting 119 132 142.4 113.4 150N912 Height to the center of the cuff arms up 110 121.8 131.9 103.3 140.5N2FGM Height of sitting down 121 130 138.9 115.4 143.4N4FGM Seat height from floor to sit 37.6 41.6 46 36 47.2N200 Back of the knee to the back of chair 40.5 45.3 51 39.1 56.7N194 Length from knee to back of chair 53 59 65.5 48.4 72.3N678 Height from floor to knee back 36.7 42.1 46 33.5 50.9N529 Height from floor to knee 48.5 54.5 59.9 30.4 65.5N381 Length from elbow to middle finger 42 47 51.4 40 54N507 Back Width arms outstretched in front 37 42 47.1 32.7 49.9N459 Seated hip width 35.5 39.1 46.5 29 56.4N859 Width thighs with knees together 29.8 33.6 42.1 26.1 52.6N775 Leg length 22.9 25.9 28.4 21.6 30.4N777 Foot width 8.5 9.8 11 8 12N776 High instep 6 8 10 5 12.3

Table 8 Results of analysis of measures for Caborca not native people. Percentile

Code Name of the measure 5% 50% 95% MIN MAX N920 Weight 50.3 68.0 89.7 46.0 105.0N805 Stature 154.2 171.7 180.2 150.6 184.2N328 Standing eye height to 144.3 161.0 170.8 143.0 175.0N23 Standing shoulder height 128.6 144.2 152.5 128.1 155.0N309 The standing elbow height 97.3 111.5 114.5 97.0 117.0N949 Standing waist height 92.6 101.8 111.5 92.4 114.0N398 Height standing gluteus 66.9 73.1 83.2 61.5 84.0N973 Standing tall on the wrist 75.0 84.7 89.2 73.0 90.0N265 Standing height to the middle finger 58.1 65.4 70.6 58.0 71.0N797 Width arms outstretched 153.7 174.3 186.2 152.0 187.0N798 Width at center chest elbows 77.0 91.3 94.7 74.3 95.0N80 Arm length from the wall 76.0 92.7 116.2 73.3 117.0N752 Distance from wall to the center of the fist 66.2 78.3 105.3 63.1 107.0N122 Standing shoulder width 37.5 43.8 48.3 35.7 49.8N223 Standing chest width 27.0 29.9 35.2 26.6 36.4N457 Standing Hip Width 31.8 35.6 37.2 30.5 38.1N639 Standing neck circumference 31.9 36.5 39.8 31.0 44.0N230 Standing chest circumference 86.6 95.0 113.6 84.0 117.0N931 Waist circumference stands 73.8 85.2 109.1 70.0 115.2N178 Standing hip circumference 94.4 101.8 112.9 91.0 117.8



N430 Head circumference 53.9 56.0 57.7 53.5 59.0N144 Distance from ear to ear on the head 33.9 36.0 39.2 33.5 40.0N165 Face width to the height of the pins 12.4 14.3 15.2 12.3 15.9N427 Head width 14.2 15.7 16.6 14.0 17.3N595 Height of the chin to the top of head 19.9 23.0 25.0 19.4 25.3N441 Head length 17.3 18.2 19.1 17.0 19.2N420 Length of hand 16.5 18.1 20.0 16.3 20.1N656 Length of the palm 9.4 10.5 12.7 9.4 19.2N411 Width of palm 7.4 8.5 9.3 7.3 9.3N402 Grip diameter 4.1 4.9 5.6 3.9 6.4N758 Seat height sitting at the head 82.0 89.0 92.7 79.0 95.2N330 Seat height sitting in the eye 72.7 78.5 82.1 69.0 82.6N25 Seat height sitting shoulder 57.3 61.7 68.6 53.5 83.0N312 Seat height to seated elbow to 90 22.2 25.5 28.7 22.0 29.6N856 Sitting thigh-high 14.2 16.2 18.3 13.7 19.8N914 Seat height to the middle finger sitting 119.5 132.6 141.0 116.6 146.5N912 Height to the center of the cuff arms up 112.9 122.8 130.1 107.8 136.3N2FGM Height of sitting down 120.5 130.0 137.7 117.5 141.4N4FGM Seat height from floor to sit 37.1 41.0 45.3 36.5 45.3N200 Back of the knee to the back of chair 41.9 46.1 49.0 41.0 49.2N194 Length from knee to back of chair 54.3 60.9 63.2 52.5 64.0N678 Height from floor to knee back 36.9 41.9 45.0 36.6 45.0N529 Height from floor to knee 47.3 54.2 58.2 47.0 58.5N381 Length from elbow to middle finger 41.5 46.5 49.7 40.7 50.6N507 Back Width arms outstretched in front 36.9 42.9 45.1 36.1 45.3N459 Seated hip width 36.9 38.2 45.2 36.6 46.2N859 Width thighs with knees together 30.9 33.6 37.9 30.0 42.8N775 Leg length 22.5 25.7 28.0 21.8 28.3N777 Foot width 8.4 9.8 10.7 8.3 11.0N776 High instep 6.9 8.1 9.4 6.3 9.9

4. CONCLUSIONS AND RECOMMENDATIONS

Working conditions are an important issue, so it should be taken into account when designing a workspace, thereby, the worker will feel more comfortable and secure and will result in higher productivity, lower absenteeism, fewer accidents, lower turnover, etc. To achieve this it is necessary to design each station or place of work according to the needs of the population that will occupy this space, this implies knowing the dimensions of the population, if not known, it can hardly meet the target, however when known, can have an assurance that the highest percentage of people who use the work area, will have no problems in terms of size and awkward postures.

By creating a product would be recommended to be used without problem by the largest number of users. The reality is that many products do not have the ability to adapt to 100% of users. For this you can follow two paths, the first would make products of various sizes in such a way that takes the opportunity to choose the one that best suits the needs of the user, the other would be to create products that are adjustable over a range measures, making it necessary to know the cost-benefits so that decision making is correct. The selection of some of the alternatives mentioned above would be facilitated if known anthropometric dimensions of the population that is expected to address. From the above highlights the importance of the results of this research.



From this research were obtained anthropometric records or letters of the working population of the city of Caborca, Sonora, Mexico, in the age ranges from 18 to 20, 21 to 23 and 24 to 27 years, and the letter Anthropometric women and men, those from Caborca and not originating in Caborca. These letters reflect the measures of the population having an age range from 18 to 27 years, within which 71% are men and 29% are women, 91% are from Caborca and 9% do not originate in Caborca.

It is hoped that this research is another step towards the creation of anthropometric letters of the Mexican population, as currently there are very few records are.

At the end of the investigation we can see the importance of the study of ergonomics and especially one of its branches which is the anthropometry, which is responsible for examining each of the different measures that make up the human body. Knowing these measures can be designed with a higher degree of reliability workstations, tools and equipment, safety equipment, clothing, etc. so we can give each user a more convenient and comfortable life. The recommendations can be made once this investigation is that it would be very interesting and important to continue to obtain anthropometric records of the total Mexican population, in order to develop equipment, workstations, tools and equipment as well as everything that needs dimensions of people, especially for the Mexican people and not have to take the actions of other countries and make adjustments later.

5. BIBLIOGRAPHY Annis 1996 James F. Annis. Aging effects on anthropometric dimensions important to workplace design. Annis Consulting, 503 Xenia Avenue, Yellow Springs, OH 45387, USA. International Journal of Industrial Ergonomics 18 (1996) 381 – 388. Baustista 2006 Ruben Bautista Balderas. Tablas antropométricas de adultos con enanismo de entre 18 a 45 años de edad para el diseño de mobiliario. Encuentro Universitario de Ergonomía. México, D.F., México 10 y 11 de Noviembre de 2006. Consultado en Diciembre del 2006. http://www.semac.org.mx/congreso/Encuentro5-4.pdf. Cavassa 2004 César Ramírez Cavassa. Ergonomía y Productividad. Editorial LIMUSA. ISBN 968-18-3797-5. Mexico, D.F. 2004. De la Vega 2004 Enrique de la Vega. La investigación de la Ergonomia en Mexico. VI CONGRESO INTERNACIONAL DE ERGONOMÍA. Guanajuato, Guanajuato, México 26 al 29 de Mayo de 2004. Consultado en Diciembre del 2006 http://www.semac.org.mx/congreso/6-6.pdf. Gosseens 1998 R.H.M. Goossens, C.J. Snijders, y T. Fransen. Biomechanical analysis of the dimensions of pilot seats in civil aircraft. Department of Product and Systems Ergonomics, Faculty of Industrial Design Engineering, Delft University of Technology, Jawalaan 9, 2628 BX Delft, The Netherlands. Department of Biomedical Physics and Technology, Faculty of Medicine and Allied Health Sciences, Erasmus University Rotterdam, The Netherlands. Applied Ergonomics 31 (2000) 9-14. 1998. Jung 2005 Hwa S.Jung. A prototype of an adjustable table and an adjustable chair for schools. Department of Industrial Engineering, Dongshin University, 252 Daehodong, Naju, Chonnam 520-714, Republic of Korea. International Journal of Industrial Ergonomics 35 (2005) 955–969. Konz 1999: Stephan Konz. Diseño de sistemas de trabajo. Editorial Limusa. 1999. ISBN 968-18-1653-6. Maldonado 2003 Araceli Maldonado, Gilberto Mota, Juan Carlos Cano, Humberto Ponce y Sergio Chávez. Rediseño de estaciones de trabajo “secado de arcilla”. V CONGRESO INTERNACIONAL DE ERGONOMÍA. Ciudad



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Biomechanical model to estimate recovery time on highly repetitive work in maquila operations

Fco. Octavio López Millán1, Enrique Javier de la Vega Bustillos1, Manuel Arnoldo Rodríguez Medina2, Armando Ayala Corona3

1Departamento de Ingeniería Industrial. Instituto Tecnológico de Hermosillo. Ave. Tecnológico S.N.

Hermosillo, Sonora, Mx. 83170 Author’s e-mail: [email protected]

2Departamento de Ingeniería Industrial. Instituto Tecnológico de Cd. Juárez. Ave. Tecnológico 1340

Cd. JuárezChih, Sonora, Mx. 32500 3Departamento de Ingeniería Industrial y de Sistemas

Universidad del Valle de México. Blvd. Enrique Mazón No. 617. Hermosillo, Sonora, Mx. 83165

Resumen: El propósito de este trabajo es desarrollar un modelo biomecánico que permita hacer

estimaciones de los tiempos de recuperación, basado en un número importante de variables

obtenidas de condiciones de trabajo reales, donde, el mismo grupo de músculos está expuestoal

trabajo repetitivo y a bajos esfuerzos. Las variables independientes están relacionadas con las

características de los trabajadores y del trabajo. Las variables de respuesta son el tiempo de

recuperación y la fatiga percibida. Los datos se obtuvieron de industrias maquiladoras del

noroeste de México.

Palabras clave: Modelo biomecánico, trabajo repetitivo, maquiladora

Abstract: The purpose of this research is development a biomechanical model allowing

estimating the recovery time based on an important number of variables, obtained from real work

conditions, where the same muscle group is exposed to repetitive work and low efforts.

Independent variables are related to personal characteristics and work characteristics. Response

variable are recovery time and perceived fatigue. Data were obtained from workers and work

stations from Maquila industries in northwest Mexico. The research is based on considerations

about anthropometrics from a Mexican population, genre and hour of work. Keywords: Biomechanical modeling, repetitive work, cumulative effect of force, maquila

1. Introduction.

Assessment of human work has been a fundamental element on the ergonomics evolution,

actually there is a wide variety of methods for the ergonomics assessment of work stations,

however, at the moment that the ergonomist needs a tool, sometimes there is the constraint which



results usually shows the most risky condition, in terms of a work muscle skeletal disorder, it

means that shows a value qualifying a single moment of work, while the work remains continuous

along the journey.

The work doing by the hands has been a very important factor on manufacturing industries,

especially on development countries, but the human being and its physical characteristics at

service of material transformation trough industrial process it is not an endless power supply,

while time pass away, physical performance could be affected and modified.

As a result of frequent exposure to work there is a risk of musculoskeletal injuries, Bernard et al

(1997) refers that it´s “were recognized as having occupational etiologic factors as early as the

beginning of the 18th century. However, it was not until the 1970s that occupational factors were

examined using epidemiologic methods, and the work-relatedness of these conditions began

appearing regularly in the international scientific literature. Since then the literature has increased

dramatically; more than six thousand scientific articles addressing ergonomics in the workplace

have been published. Yet, the relationship between MSDs and work-related factors remains the

subject of considerable debate.”

Continuous and repetitive tasks could lead to disorders on the soft tissues on joints. The tissues

that frequently get injured as a result of exposure to occupational biomechanical hazards are

ligaments, tendons and muscles. Other structures affected less frequently are cartilage and

bones. All biological tissues are visco-elastic; hence, their mechanical properties are time- and

strain rate-dependent. The tissue visco-elastic property determines the duration required for

complete mechanical recovery, Kumar (2001).

Disorders on the soft tissues are well known as cumulative trauma disorders (CTD´s), it´s

basically a combination of factors or occupational activities that leads to these injuries, Keyserling

et al (1993) includes repetitive motions, forceful exertions, and awkward postures. Bernard et al

(1997) presents an evaluation and summary of the epidemiologic evidence focuses on disorders

affecting the neck and the upper extremity; including tension neck syndrome, shoulder tendinitis,

epicondylitis, carpal tunnel syndrome, and hand-arm vibration syndrome, which have been the

most extensivelystudied in the epidemiologic literature. Combination of these risk factors on the

same activities increases the possibility of injuries in wrist and shoulder while neck disorders are

related to awkward posture, for instance.



CTD´s cost days and money so there are relevant, the BLS (2005) reports 1,234,700 workdays

lost in USA. In the same year there were 270,890 reported injuries in low back. Bernard et al

(1997) reports 32% of injuries were due to excessive efforts or repetitive tasks. In specific, 65% of

cases were caused by effort to lifts objects or materials, affecting low back, 52% were caused by

pushing or pulling. But it´s not only low back injuries, the report includes 47,681 shoulder injuries

and 92,576 injuries associated to repetitive movements, 55% of that affected wrist.

Muggleton et al (1999) refers to injuries related to work as typical injuries on XX century and

consider it´s as the bigger of problems on occupational wealth. On United Kingdom, upper limb

musculoskeletal disorders are the most frequent just below low back pain injuries. CTD external

causes says, are related with the pressure on industry business for increasing productivity. In

consequence, costs for; medical attention, incapacities days, lost workdays, employs rotation,

absenteeism costs, have been increased too.

Viikari-Juntura (1997), notes the need of programs and strategies to prevent occupational

injurieswhile lost days increases on industrial countries, as well as development countries. The

European Union is working on rules and laws about occupational injuries, focusing in harmonizing

it´s legislation.

In México, according to the IMSS (Mexican Institute for the Social Safety) in 2006 were reported

138,700 work injuries in hand-wrist and low back area. The Mexican legislation and rules doesn´t

make any difference between accident and occupational injuries.

In northern México, in Border States the data are the follows:

Table 1. Work related injuries in Nothern Mexico..

State Injuries Hand-wrist Low back

Nuevo León 29054 10425 3264

Baja California 16308 6025 2041

Sonora 12074 3678 2127

Tamaulipas 11823 3691 1734

Chihuahua 1762 453 239

Coahuila 1425 358 149



1.1 Occupational injuries. The risk factors are related with injuries in joints and soft tissues.

There are several terms to name it, Grieco et al (1998) defines as “Work Musculoskeletal

Disorders; WMSD”, but frequently is used as a synonymous “Cumulative Trauma Disorders

(CTD´s)” or “Repetitive Strain Injuries (RSI)”. Grieco et al (1998) associate as characteristics of

these injuries the follows: Its origin is due to several factors (occupational and personal), it take

long time to develop the disorder, recovery are used to be slow and probably never at 100%,

frequently involves groups of tendons and muscles and that one’s caused by nerves pressed are

de lesser frequents but the painful and costly.

1.2 Ergonomic Risk Factors. To understand the musculoskeletal disorders problem, is required

to identify the risk factors associated to these kinds of injuries. There is a wide literature about it

and its don´t surprise, the problem has been studied for years and many point of views and results

of research converge on the causes or risk factors, Colombini (1998) recognize mainly four risk

factors; repetitive movements (frequency), force applied to the task, awkward postures and lack of

enough recovery time on each work cycle. Muggleton (1999) includes vibration as a risk factor for

the hand-wrist. McAtamney y Corlet (1973) refers to the risk factors as external factors, including

a consideration for static work load on muscles. Furthermore, highly repetitive work may directly

damage tendons through repeated stretching and elongation, as well as increase the likelihood of

fatigue and decrease the opportunity for tissues to recover Keyserlin et al (1993).

The focus of this project is on the repetitive effect on recovery time based on manufacturing

activities at high level of repetition which is the most of the tasks that operators perform on

maquila industries in basically all Northern of México.

Is well known the wide ergonomics assessment techniques available in present, Liand Buckle

(1999) mentioned that exposure to risks for potential work-related musculoskeletal injuries has

been assessed using a variety of methods, including pen and paper based observation methods,

videotaping and computer-aided analysis, direct or instrumental techniques, and various

approaches to self-report assessment.



The purpose of this research is develop a model to describe the effect of repetitive task and

predict the recovery time for continuous task and includes subjective factors as perceived fatigue,

this last factor in order to explain the presence of tape on finger tips or wrist protections.

2. Method. It is very relevant to the success of this project obtain the data from real conditions, that means

going to the assembly production lines on maquilas and get the data. The first step consists

tochoose the work stations, video recorder it, get data: anthropometric and operational and

perceived fatigue.

We appreciate the support from the maquila, they let Us to see the process, mostly of it is

confidential, for the first step 23 workstations were analyzed, the variables included are; height,

weight, angle on shoulder (RH) to perform a sustained effort and the time on that posture.

Additionally, a perceived fatigue questionnaire was ask to answer for, it qualifies from 0 to 3

presences of any symptoms like numbness, pain or stiffness, were 0 means no symptom at the

end of the work shift, 1 means seldom times remember any symptom, 2 is related to occasionally

feels any symptom and 3 are related to frequent symptoms. For each workstation were

considered two activities involving shoulder posture.

On second step data were analyzed using 3D SSPP© and Rohmert formula to estimate

recuperation time for each operator. The third step involves the linear regression analysis and the

Bayesian approach to optimize the time recuperation model. WinBUGS is the tool for Bayesian.

3. Results All collected data are at the end, summarizing, 46 data were analyzed for the 23 operators; it’s

due to the use of two different exertion times. On each job the angle on shoulder was measured

and every workstation was modeled using the 3D SSPP© software to obtain the moment on the

shoulder. Moment and sustained effort time on seconds were used to introduce as data to

Rohmert formula, the result is the recovery time for the shoulder, expressed on seconds on

different posture, for every 60 seconds of work.

3.1 Statistical analysis. The analysis was made using SPSS© software. In the beginning, the

moment on shoulder was considered as a variable, it’s give an excellent correlation r = .918 with



an adjust r = .819 which means a high explanation to the variability of the data, but moment on the

practice is not an easy data to calculate, that´s why we optioned a less efficient model but easy to

use and understand.

Subtracting the moment the model summary is:

The linear regression model obtained is shown as follows: Coefficientsa

Model

UnstandardizedCoefficients

StandardizedCo

efficients

t Sig. B Std. Error Beta

1 (Constant) -28.025 29.563 -.948 .348

Estatura .220 19.919 .001 .011 .991

Peso -.115 .079 -.133 -1.454 .153

Angulo .466 .082 .436 5.684 .000

FatPer 1.068 1.097 .077 .974 .335

TESF 1.208 .128 .716 9.451 .000

a. Dependent Variable: TREC

Expressed on the mathematical form, the model is:

Recovery Time= -28.025 + .22*Height - .115*Weight + .466*Angle + 1.068*Perceived Fatigue

+ 1.208*Sustained effort time

3.2 Bayesian Analysis.The Bayesian analysis is included in order to optimize the linear

regression model coefficients, on this approach; coefficients leave the parameter condition in the

model becoming a variable on the model. WinBUGS is a tool developed to perform Bayesian,

based on Markov Chain and Monte Carlo methods the software allows simulate a great number of

repetitions.



There are some additional considerations to made; variables fit a normal distribution. On every

variable the software run more than 10,000 iterations.

The linear regression model has change as follows:

Recovery Time= -44.13+ 5.22*Height -0.1227*Weight + 0.5464*Angle -0.02*Perceived Fatigue

+ 1.534*Sustained effort time

The resulting model is based on the original linear regression model but coefficients become

variables with its own statistical distribution.

Bayesian analysis is a very useful tool when experiments are limited and especially when the data

come from human characteristics and a cross functional approach are used on the research.

4. Discussion The linear regression model optimized can now be used to estimate recovery times on repetitive

operations but is necessary draw some limitations; to verify the accuracy of the model it was run

with different exertion times, the model result on negative values for recovery time when the

exertion timeis below 10 seconds and for exertion times higher than 30 seconds results are

considerably greater that could made efficient on process get on low values, so it has and impact

on costs.

In test stage, when exertion times are below 10 seconds, recovery time calculated by Rohmert

formula result on values around 2 seconds or lower, that could be interpreted like low risk

operations due to repetitiveness and classifieds on green codes. On the other hand exertion time

over 30 seconds results on high repetition rates having an effect on sustain effort and

consequently on a high risk for an occurrence of occupational injuries.

The application of the model is not complicated, the input variables are the predictors variables;

the height is expressed on meters, the weight is in kilograms, the angle on the shoulder can be

measured using a goniometer, perceived fatigue could be get asking to the operators for the

presence of any symptom described before and exertion time can be measured by a chronometer

or analyzing the video time counter. Once the data are collected, introduce it in the formula and

the results are expressed on how many seconds per every 60 seconds cycle are needed to

recover a group of muscles from fatigue due to the job.

The application of the model could be extensive on a future to other groups of muscles, for

instance low back muscles or wrist articulation, increasing the focus of the research, increasing



the analysis of different jobs when those are repetitive. At the end the final purpose is bringing a

little more on safety on daily performance allowing to people return home with a little bit more

energy to share with the family.

References Bernard, B. (1997). “Musculoskeletal Disorders and Workplace Factors; A Critical Review of

Epidemiologic Evidence for Work-Related Musculoskeletal Disorders of the Neck, Upper

Extremity, and Low Back”.Centers for Disease Control and Prevention, National Institute for

Occupational Safety and Health (NIOSH).

Bureau of Labor Statistics (2007).“Injuries, Illnesses, and Fatalities (IIF) program”.www.bls.gov.

Colombini, D. (1998) 'An observational method for classifying exposure to repetitive movements

of the upper limbs', Ergonomics, 41:9, 1261 – 1289.

Grieco, A. (1998). “Application of the concise exposure index (OCRA) to tasks involving repetitive

movements of the upper limbs in a variety of manufacturing industries: preliminary validations”,

Ergonomics, 41:9, 1347 - 1356

Instituto Mexicano del Seguro Social, (2006). “Información estadística en salud; accidentes de

trabajo (1). www.imss.gob.mx

Keyserling, W. M., Stetson, D. S., Silverstein, B. A. and Brouwer, M. L. (1993) “A checklist for

evaluating ergonomic risk factors associated with upper extremity cumulative trauma disorders”,

Ergonomics, 36:7, 807 – 831.

Kumar, Shrawan (2001) 'Theories of musculoskeletal injury causation', Ergonomics, 44:1, 17 –

47

Li G., Buckle P. (1999).“ Current techniques for assessing physical exposure to work-related

musculoskeletal risks, with emphasis on posture-based methods”. Ergonomics, 42; 5, 674 – 695.

McAtamney, L. Corlet, N., (1973).“RULA; A survey method for the investigation of work-related

upper limb disorders”. Applied Ergonomics; 24(2), 91-99.

Muggleton, J. M., Allen, R. and Chappell, P. H.,(1999.) “Hand and arm injuries associated with

repetitive manual work in industry: a review of disorders, risk factors and preventive measures”,

Ergonomics, 42:5, 714 – 739.

Rohmert Walter (1973). “Problems in determining rest allowances”. Applied Ergonomics, 4.2 91-

95.



Viikari-Juntura, Eira R. A. (1997) 'The scientific basis for making guidelines and standards to

prevent work-related musculoskeletal disorders', Ergonomics, 40:10, 1097 – 1117

DATA

Height Weight Shoulder Angle

Perceived Fatigue

T exer T rec

1.62 64 60 3 15 9.84

1.61 59 45 2 14 5.23

1.53 61 45 0 12 3.39

1.56 60 40 1 18 7.72

1.61 55 40 2 17 6.53

1.61 65 45 3 10 2.73

1.58 61 40 3 15 5.3

1.54 58 35 2 20 7.19

1.60 66 55 3 15 9.51

1.65 58 35 3 19 8.35

1.64 67 65 2 13 8.39

1.56 57 55 3 16 8.01

1.58 56 60 3 21 17.25

1.62 65 40 2 18 9.99



1.61 67 46 2 15 1.33

1.72 86 40 2 16 2.54

1.62 74 40 2 14 0.91

1.58 81 55 3 19 12.41

1.58 54 30 3 21 6.82

1.63 56 50 2 25 24.98

1.62 64 60 3 21 22.05

1.61 59 45 2 26 23.11

1.53 61 45 0 24 17.88

1.56 60 40 1 29 24.27

1.61 55 40 2 27 19.82

1.56 52 30 2 26 9.62

1.61 65 45 3 24 35.11

1.58 61 40 3 26 19.83

1.54 58 35 2 29 17.54

1.60 66 55 3 23 26.52

1.60 53 35 2 22 9.04

1.55 50 40 2 23 9.95

1.65 58 35 3 27 19.4



1.64 67 65 2 21 26.51

1.56 57 55 3 29 33.39

1.58 56 60 3 25 26.22

1.62 65 40 2 28 28.84

1.68 102 45 3 22 14.33

1.67 77 30 3 24 2.05

1.72 86 40 2 28 9.75

1.52 75 39 3 22 0.86

1.62 74 40 2 21 2.42

1.58 81 55 3 30 37.15



VERIFICATION OF MAXIMUM ACCEPTABLE WEIGHT OF LIFT, TABULATED IN LIBERTY MUTUAL TABLES, IN WOMEN OF CABORCA

Jesús Rodolfo Guzmán Hernández1, Joaquín Vásquez Quiroga1,

Enrique Javier De La Vega Bustillos2

1 Grupo disciplinar de Ergonomía, Programa de Ingeniería Industrial, Universidad de Sonora Unidad Regional Norte, campus Caborca.

Caborca, Sonora, México, [email protected], [email protected]

2Maestría en Sistemas Industriales Instituto Tecnológico de Hermosillo

Hermosillo, Sonora, México [email protected]

RESUMEN: Esta investigación se realizo con la intención de verificar la aplicación de los datos,

de peso máximo de levantamiento (MLW), tabulados en las Tablas Liberty mutual, en la

población laboral femenina de Caborca, Sonora, México. El experimento se limito a tareas de

levantamiento vertical, frecuencia de uno por minuto, cajas de 34 cm de ancho (distancia desde el

cuerpo), distancia de movimiento 51 cm, en tres niveles de levantamiento, bajo, que corresponde

a levantamientos entre el suelo y la altura de nudillos, medio, de altura de nudillos a altura de

hombros y alto, de altura de hombros a brazo extendido. Ésta fue realizada con alumnas

estudiantes del programa de Ingeniería Industrial y de Sistemas adoptando el supuesto de que

ellas pudieran estar formando parte de la fuerza laboral de las empresas establecidas en la

región. Como resultado de este experimento se observo que los peso máximos tabulados en la

Tabla Liberty Mutual para tareas similares a las de este experimento, son cuantitativamente

mayores y existe evidencia estadística suficiente para rechazar que se pueden aplicar a la

población laboral bajo estudio.

Palabra clave: levantamiento de carga mujeres, tareas de levantamiento mujeres, máxima peso aceptable ABSTACT: The intention of this investigation was verify the application of maximum lifting weight

data tabulated in the Liberty Mutual Tables (MLW), on the female labor population of Caborca,

Sonora, Mexico. The experiment was limited to vertical lifting tasks, frequency of one per minute,

boxes of 34 cm of wide (distance since the body), distance of movement 51 cm, in three levels of



lifting, low, that corresponds to lifting among the floor and the height of knuckles, medium, of

height of knuckles to height of shoulders and high, of height of shoulders to arm extended. This

investigation was done with 14 students, female gender, of the program Industrial and Systems

Engineering, with the assumption that they could be part of the workforce of firms established in

the region. As a result of this experiment was observed that the information of maximum

acceptable weight tabulated in liberty mutual tables for similar tasks this experiment are

quantitatively greater and there is sufficient statistical evidence to reject that we can apply it to

working population under study.

Keyword: women lifting weight, women lifting tasks, maximum acceptable weight

1. INTRODUCTION Webster et al (1994) suggest that low back pain, associated with manual handling of loads,

has been recognized as a major problem worldwide is the most costly injury in the industrial world.

De la Vega (2006), citing The National Institute for Occupational Safety and Health (NIOSH) 1991,

indicates the factors that directly influence the risk of lower back injuries are the weight and

dimensions of the object, the distance is raised, lowered, pulled or pushed, and the repetition rate,

as well as indirect factors such as age and physical condition of the worker. The consequences of

ignoring the weight limit on the repetitive handling of loads can result in decreased performance at

work and presents a risk of back pain that can become a cumulative trauma disorder (CTD) Putz-

Anderson (1994). There are some studies about amount of weight that an individual is capable of

lifting and about task design of the handling manual of loads with minimal risk of injury considering

their characteristics and physical abilities. The reports of these studies represent guides to the

industry which requires manually moving loads repeatedly. Among the most widely used guides

include the NIOSH equation and the Liberty Mutual tables. The first is a tool through which,

considering 7 factors involved in a lifting task, calculate the recommended weight limit (LPR) and,

once known, is calculated the Lifting index that he is the ratio between the load weight and the

recommended weight limit. The values that can take this index may fall into three risk zones,

namely: limited risk (lifting index <1) where the majority of workers performing these tasks should

have no problems, moderate increase in risk (1 < lifting index <3) situation in which some workers

could suffer illness or injury when performing these tasks same should to be redesigned or

assigned a selected workers on which shall be strictly control; sharp increase in risk (lifting index>



3), this type of task is unacceptable from an ergonomic standpoint and should be changed.

Moreover, the Liberty Mutual Company has developed the Liberty Mutual tables or tables of

Snook which are a collection of tables which sets the maximum acceptable weight for help to

control the risk of injury in the lower back in activities of manual handling of loads. In particular for

lifting load, use the frequency of the task, the distance of movement of the load, the height at

which the movement is placed, the size of the object and its grips and the horizontal distance

(distance from the body) like parameters. With these parameters, the maximum acceptable weight

it is tabulated in 10, 25, 50, 75 and 90 percentiles for male and female peoples. These studies

and the respective conclusions were generated from the experimental data obtained of developed

workers populations countries and the findings and their recommendations they are apply in

Mexico without considering that data were obtained without including the characteristics and

physical abilities of the Mexican population.

In the Mexican Republic from 1992 to 2002 the Mexican Social Security Institute reported

cases of 191.639 spine injuries, including back pain, accounting for 4.7% of total workplace

injuries. Likewise, there is 42.422 dorsopatias with total disability in the period reported, including

low back pain associated with lifting loads, representing 18.98% of total disability (Review IMSS

2004), which indicates the relevance of the lesions of the spine. From the above, born the need to

conduct this study which seeks to identify injury risks in applying the criteria of acceptable loads in

the female population in Caborca, Sonora, Mexico, on grounds that it may be a cause for lower

back pain that result of the manual materials handling, a problem that is occurring more often in

companies. This raises the question "The maximum acceptable weight, reported by the Liberty

Mutual tables for women, applies to women workers of Caborca? About this question the present

investigation was made and it focuses only on tasks of vertical lift in frequency of one per minute,

boxes width 34 cm, (distance from the body), movements 51 cm distance and three levels lifting:

low , corresponding to uprisings between the ground and knuckle height, medium level, from

height to knuckle to shoulder height and from shoulder height to arm's length.

2. OBJETIVE

The objective of this study is to identify risks in applying the criteria of maximum acceptable

charges Liberty Mutual tabulated in Tables in the female working population Caborca, Sonora,



Mexico, because it can be one of the causes of lower back pain , resulting from manual material

handling, is a problem that is occurring more often in business. This led to pose the question "The

maximum acceptable weight women, the tables set by Liberty Mutual, is applicable to workers in

Caborca?

3. MATERIALS AND METHODS

Details of the experiment, from where the Liberty Mutual Tables were made, it is found in the

publications of Ciriello et al 1983, 1990 and 1991. The experiment was conducted using

psychophysical approach. This approach requires that the subject is motivated by an incentive,

and He,based on the perceived sensations, select the maximum load that it considers may sustain

for a working day of 8 hr. According to Shoaf (1997), the major hypothesis of the psychophysical

approach is that: at a given time, adjusted to 40 minutes, a person is able to predict the maximum

weight or force that could be manipulated during a period of 8 hr; Mital (1983) states, people can

estimate the amount of weight that can lift comfortably in 8 hr, based on experiencing fatigue in 25

min and, hopefully, the weight selected by the subject is the same whether the person continues

lifting it for 8 hr; Additionally, he states: there is no literature evidence to validate this claim.

Under these criteria, basically, the subject is given control of the weight of the load, the participant

monitors their own sensations of fatigue and adjusts the weight which he believes could bear. All

other variables such as task frequency, load weight, distance of movement, etc.. are controlled by

the experimenter. The participants in this experiment were 14 young female between 19 and 22

years, they were university-level students they could be part of the workforce in the Caborca

region. All signed in writing that they were free of lower back injury and had no cardiovascular

disease. They used casual clothing and tennis shoes, jeans and loose shirts.

To all participant in the experiment and for verify that the heights and distances of

movement of loads in lifting tasks was be according to the experiment of Snook, were taken the

anthropometric measures of weight, height, knuckle height, acromial height and extended arm

height. Given the limited experience of the participants in manual handling of loads were given a

belt to help keep your lower back straight. The participants were given training equal to the

training done it in Ciriello et al (1983) experiment, to familiarize them with the activities to

performed and gain experience in adjusting the load, increase or decrease according to their own



perceptions, they doing efforts themselves but without reaching a state of extreme tiredness,

weakness, overheating or running out of breath, this, doing movements of vertically lifting , at a

distance of 51 cm, with bending the knees and keeping your back straight, no turns or twists,

without pull or push the load. For four consecutive days of tasks were performed lifting low (floor

knuckle hight), increasing gradually the time. During first and second day were made a task for 10

min with light load and heavy load respectively, the third day two tasks of 10 minutes each with

light and heavy load respectively, without resting, the fourth day two tasks of 15 minutes with light

load and heavy load respectively, without resting. The fifth, sixth and seventh days were for do the

data collection. The daily tasks were made with duration of 40 minutes divided into two periods of

20 minutes each one, without rest between periods, in the first period it gave them a heavy load

and in the second light load, all randomly selected.

Each day were made only the task for each level indicated for in the lifting Liberty Mutual

tables, namely between floor level and knuckle height ( lifting low), between knuckle height and

acromial height (lifting medium) and between airmail height and arm extended length (lifting

height). For the experiment were used rigid polypropylene boxes with length of 55 cm (distance

between hands), 34 cm wide (distance from the body) and 17 cm in height. The handgrips were

located at half of the distance from the body and 15 cm from the floor of the box. The box

contained a false bottom in which was placed a burden whose weight was randomly selected as in

the experiment of Ciriello and Snook (1990). This hidden weight was not known by the participant

in an attempt to minimize the visual effect. The load management was welding rods and it was

used a balance T31P Ohaus, a decimal minute chronometer, a bell and shelves height-adjustable.

For each level of uprising were select, at random, 14 heavy load values, between 32 and 45 kg,

then was decreased in 3 kg each, which corresponds to the box weight, and the lid of the double

bottom, the resulting value were divides random, to place the burden in the hidden compartment

and the visible, subsequently the same procedure was performed for 14 light loads between 2 and

18 kg, Snook (1990). These two procedures were repeated for each of the three levels of lifting

the experiment. In the collection of field data were given in the first period a heavy load and the

second period a light load., Participants adjusted the load in each period, they decreased or

increased it according to their own perceptions until it represented the maximum they could lift in 8

hr of task, if the load of the second period was between 15% of the first, the average of the two



loads is registered as the maximum acceptable load of the participant, otherwise the information is

removed and a new test was performed.

4. RESULTS AND DISCUSSION According to the working hypothesis raised in this investigation, if the maximum acceptable weight

(MAW) of Table Liberty Mutual is applicable to the female population of the Caborca region, then

the percentile distribution of the maximum load obtained from the participants, must statistically to

exist a matching with the distribution of the liberty mutual table percentiles. Under this approach

was performed the analysis for low level lifting. The results of the analysis are show in Table No 1

Table 1 Analysis of field data, low level

From the above table it is seen that for the 10th percentile there is not sufficient evidence to

reject the null hypothesis. For 75, 50 and 25 percentile the significance levels of the test statistic

permit reject the null hypothesis. The 10th percentile, has significance level to accept Ho but, is

not feasible to accept the hypothesis that it applies the maximum load in the female working

population Caborca because there is no real data to the percentiles 25 and 10, for what there is

certainty to make the decision that both hypotheses may be rejected.

For mid level lifting was performed an analysis similar to the previous data, the obtained

information shown in Table No 2

MAW(Kg)

90 11 P0 = 0.90 p= 0.79 0.08 -1.38 0.10 No rechazar Ho75 14 P0 = 0.75 p= 0.36 0.12 -3.25 0.00 Rechazar Ho50 16 P0 = 0.50 p= 0.21 0.13 -2.23 0.02 Rechazar Ho25 19 P0 = 0.25 p= 0.00 0.12 -2.08 0.03 Rechazar Ho10 22 P0 = 0.10 p= 0.00 0.08 -1.25 0.12 No rechazar Ho

liberty mutual tabla data Hypotesis test

percentileNull hypothesis statistical test

standard desviation t α decisión



Table 2 Analysis of field data, medium level

In the analysis can be seen that, for the 90, 75, 50 and 25 percentiles, the levels of significance of

the test statistic are able to reject the null hypothesis. The 10th percentile has a high significance

level to not accept H0 but there is not feasible to accept it because, there is not real evidence.

For high lifting, was performed the analysis data that it is show in table3.

Table 3 Analysis of field data, hight level

In this last analysis presents a situation similar to the results for lifting low, one can see that

for the 90th percentile there is no sufficient evidence to reject that, at this level, we can apply the

maximum weight indicated by the table, for the percentiles 75, 50 and 25 the level of significance

of the test statistic is at able to reject the null hypothesis. For the 10th and 25th percentiles, same

MAW(Kg)

90 10 P0 = 0.90 p= 0.64 0.08 -3.25 0.00 Rechazar Ho75 12 P0 = 0.75 p= 0.50 0.12 -2.08 0.03 Rechazar Ho50 14 P0 = 0.50 p= 0.07 0.13 -3.31 0.00 Rechazar Ho25 16 P0 = 0.25 p=0.00 0.12 -2.08 0.03 Rechazar Ho10 18 P0 = 0.10 p= 0.0 0.08 -1.25 0.12 No rechazar Ho

liberty mutual tabladata Hypotesis test



MAW(Kg)

90 9 P0 = 0.90 p= 0.77 0.08 -1.63 0.06 No rechazar Ho75 11 P0 = 0.75 p= 0.31 0.12 -3.67 0.00 rechazar Ho50 12 P0 = 0.50 p= 0.08 0.14 -3.00 0.01 rechazar Ho25 14 P0 = 0.25 p= 0.00 0.12 -2.08 0.03 rechazar Ho10 15 P0 = 0.10 p= 0.00 0.08 -1.25 0.12 No rechazar Ho

datos correspondientes a 13 participantes



liberty mutual tabla Hypotesis test



that in previous analysis is not feasible to accept the hypothesis Ho because there is no real

evidence.

5. CONCLUSIONS

With the results and analysis of the data above we can accept that, in general, there is not

sufficient evidence to accept that the maximum weight recommended in Liberty Mutual Table for

lifting in women, in vertical lifting for frequency of one per minute, boxes of 34 cm wide (distance

from the body), movement distance of 51 cm, at the three levels of survey, can be applied to the

female workforce of the Caborca region without running the risk of injury. Given this information

we can conclude that, it is not appropriate to apply the recommendations in Table Liberty Mutual

in the female working population in the Caborca region since it is possible that this population has

a lower lifting capacity or possibly with a less dispersion in capacity lifting. As a result of this

research we recommend that define the acceptable maximum weights in lifting burdens on women

in different regions of our country since there are no recommendations in this regard and are a

cause of interest public health

6.REFERENCES Ciriello, VM and Snook, SH 1990., Ergonomy 1990, vol 33, no.3 ,187-200, "The effects of

container size, frequency and extended horizontal reach on maximum acceptable weights of lifting

for female industrial workers."

Ciriello, VM and Snook, SH 1991, Ergonomy 1991, Vol 34, No 9,1194-1213, "The design of

manual handing tasks: revised tables of maximum acceptable weights and forces".

De La Vega Bustillos, Enrique 2005, "checklists, methods and mathematical models for ergonomic

evaluation of work environments", Technological Institute of Hermosillo

http://www.estrucplan.com.ar/articulos/verarticulo.asp?IDArticulo=982 visited in June 2009

Mital, Anil (1983), Human Factors, 1983, 25 (5), 488-49, The Psychophysical approach in manual

lifting, a verification study.

National Institute for Occupational and healt (NIOSH), 1991, "Scientific support documentation for

revised 1991 NIOSH lifting equation".

Putz Anderson, V (1994) "Cumulative Trauma Disorders. A Manual for Musculoskeletal Diseases

of the Upper Limbs. Taylor & Francis, London.



Snook, SH and Ciriello, VM 1983, Human Factors, 1983.25 (5), 473-483, "A study of size,

distance, Height and Frequency Effects of manual handling tasks



Force analysis in hands on highly repetitive work in maquila operations

Fco. Octavio López Millán1, Enrique Javier de la Vega Bustillos2, MaríaJesúsTéllez Moroyoqui1, LodevarPavlovichOviedo2 , Bertha Leticia Ortiz Navar3

1Departamento de Ingeniería Industrial.

Instituto Tecnológico de Hermosillo. Ave. Tecnológico S.N. Hermosillo, Sonora, Mx. 83170

Author’s e-mail: [email protected] 2División de Estudios de Posgrado e Investigación.

Instituto Tecnológico de Hermosillo. Ave. Tecnológico S.N. Hermosillo, Sonora, Mx. 83170

3Departamento de Ingeniería Industrial. Instituto Tecnológico de Nogales. Ave. Instituto Tecnológico #911.

Nogales, Sonora, Mx. 84065

Resumen: Esta investigación se enfoca a analizar la fuerza como una función de tiempo en datos

obtenidos en condiciones reales, considerando trabajo altamente repetitivo, donde las manos y

dedos están expuestos a trabajo repetitivo y bajos esfuerzos. Se utilizo el diseño genera de

medidas repetidas para analizar el comportamiento de la fuerza para ambas manos y pulgares.

La hora, el turno y el día de trabajo fueron considerados como factores. La fuerza fue medida de

la sexta a la octava hora en un intervalo de una hora, mientras que la semana empezó el lunes;

el monitoreo fue de una semana. Los datos fueron obtenidos de plantas maquiladoras de las

ciudades de Hermosillo y Nogales Sonora.

Palabras Calve: Fuerza en manos, fuerza en pulgares, trabajo repetitivo, efecto acumulado de la fuerza, maquila. Abstract: The focus of this research is analyze how force is going as a function of time in data

obtained from real work conditions, considering highly repetitive work, where the hands and

fingers are exposed to repetitive work and low efforts. The repetitive measurement general design

was used to analyze force behavior for both hands and both thumbs. The hour on the shift and the

day week are the factors. Force was measured from the sixth hour to the eight hour on one hour

interval, while the week day starts on Monday; the monitor is for a week. Data were obtained on

maquila plants in Hermosillo and Nogales Sonora.

Keywords: Hands force, thumbs force, repetitive work, cumulative effect of force, maquila.



1. Introduction The work doing by the hands has been a very important factor on manufacturing industries,

especially on development countries, but the human being and its physical characteristics at

service of material transformation on industrial process it is not an endless power supply, while

time passthrough the day, physical performance could be affected and modified.

As a result of frequent exposure to work there is a risk of musculoskeletal injuries, Bernard et al

(1997) refers that it´s “were recognized as having occupational etiologic factors as early as the

beginning of the 18th century,however, it was not until the 1970s that occupational factors were

examined using epidemiologic methods, and the work-relatedness of these conditions began

appearing regularly in the international scientific literature. Since then the literature has increased

dramatically; more than six thousand scientific articles addressing ergonomics in the workplace

have been published. Yet, the relationship between MSDs and work-related factors remains the

subject of considerable debate.”

To understand the musculoskeletal disorders problem, is required to identify the risk factors

associated to these kinds of injuries. There is a wide literature about it and its don´t surprise, the

problem has been studied for years and many point of views and results of research converge on

the causes or risk factors, Colombini (1998) recognize mainly four risk factors; repetitive

movements (frequency), force applied to the task, awkward postures and lack of enough recovery

time on each work cycle. Muggleton (1999) includes vibration as a risk factor for the hand-wrist.

McAtamney y Corlet (1973) refers to the risk factors as external factors, including a consideration

for static work load on muscles. Furthermore, highly repetitive work may directly damage tendons

through repeated stretching and elongation, as well as increase the likelihood of fatigue and

decrease the opportunity for tissues to recover Keyserlin et al (1993).

This work is focused in finding the relationship between frequency and the force that people can

exert as a function of time and some anthropometric characteristics, the approach is; on the latest

hours of the shift work, force become to decrease significant, at least statistically and there is a

relationship between force and anthropometrics.

2. Method

One objective was collect data in working conditions, so the “experiment” was planned as follows:



• Find a process with highly repetitive operations; it is more than 300 units per hour.

• The job involves extensive use of the hands and the fingers.

• The anthropometrics measurements are for the hands and some generals:

o Length of the hand.

o Width of the hand.

o Height of the hand.

o Width of the wrist

o Height of the wrist

o Height of the thumb

o Width of the thumb

o Height of the middle finger

o Width of the middle finger

• The force on handgrip and thumb grip is measure with a Jamar© hand dynamometer and

finger dynamometer. Every day 3 measurements are made every half hour from the sixth

hour for the handgrip and finger grip for each side of the hands.

• All data is collected and analyzed on statistical software (SPSS©)

• Multiple linear regression is the tool to analyze the relationship between force and

anthropometrics.

• The repetitive measurements general model is used to analyze the force within hours and

within days.

• The data are from maquilas on Hermosillo and Nogales, Sonora, Mex.

3. Results Is relevant to mention, again, how important get data from working conditions is, there was about

50 operators who they were asked for to participate with the measurements for anthropometrics

and force exertions, we appreciate that very much as well the maquila support to achieve the

purpose of the research. Once data were collected and organized on worksheets next step is

proceed to statistical analysis.

The first part is finding the relationship between anthropometrics and force for each side on the

hands, before the linear regression analysis, principal components was run to discriminate and



group variables, the next tables show it:The first iteration includes all variables resulting on seven

groups and .717 acceptable KMO value, results are:

Table 1. Total variance explained

. The first rotated component matrix shows how variables are grouped in the seven groups: Table 2 Rotated Component Matrix



After several iterations, the target is find two groups; this final rotated matrix is next: Table 3 Final Rotated Component Matrix

As values are shown on the table 4.3 the groups are formed with the higher coefficients; a first

group is for; gender, height, weight and hand force. The second group are formed with; hand

length, hand width, thumb width, thumb length and wrist width.

Once groups are formed the next is linear regression analysis, the purpose here is just to found

some kind of statistical relationship between variables or personal and force, next table shows the

better relationship:

Table 4 Linear Regression Model Predictor variables were; height, weight, thumb width, wrist width and hand length. Response

variable is hand force.

Linear regression shows a relationship between variables and force, that in general conditions, so

next step is the analysis of force as a function of time.



Force behavior was tested using repetitive measurements general model for each hand.

Additionally some extra test was run in order to probe variances and differences between hours

and days. Results are in next tables. The first test is for right hand and the hour of the shift, table 5

shows descriptive and table 6 shows Mauchy´s sphericity test.

Table 5.Descriptive statistics for right hand and hour .

Table 6.Mauchy´ssphericity test . Significance on Mauchy´s test is 0.00 that means differences between variances are not equals,

so is necessary run the Bonferronistest for multiple comparisons, this test shows in what hour are

a difference in average exerted force on right hand, table 7 shows it.

Same proceed is for the left hand and next tables shows results for descriptive statistics,

significance on Mauchy´s test is 0.00 that means differences between variances are not equals,

so is necessary again run the Bonferronis test for multiple comparisons, this test shows in what

hour are a difference in average exerted force on left hand.

All statistical tests are for a 95% confidence level.



Table 7.Bonferroni´s pair comparisons for right hand

. Table 8.Descriptive for left hand

. Table 9.Mauchy´s test for left hand.



Table 10.Bonferroni´s pair comparison for left hand.

Same proceed is for both hands but the analysis is now within week days. Next tables shows

results for descriptive statistics, significance on Mauchy´s test is 0.00 that means differences

between variances are not equals, so is necessary again run the Bonferronis test for multiple

comparisons, this test shows in what day are a difference in average exerted force the hand. Table 11.Mauchy´s test for day and right hand

. Right hand force descriptive are:



Table 12.Descriptive statistics for right hand and day.

Table 13.Bonferroni´s comparison pair test

.



Table 14.Mauchy´s test for day and left hand

Table 15. Descriptive statistics for left hand and day

Table 15.Bonferroni´s comparison pair test for left hand and day.



4. Discussion In an implicit form the purpose of this research was to show how force depend on anthropometric

characteristics and how force is related with fatigue with a clear decrease pattern on force

behavior trough hours and days.

The first part tested by principal components and linear regression is positive; a statistical

relationship does exist between hand and finger anthropometrics and force, in detail table 3 shows

that, all values on above .600 on second group are related with the explanation of variance.

In the second part the expected was that the greater values for hand forces were on the early hour

and Monday, but results are not in that direction, for right hand force within hours, table 7 shows a

difference only between the first hour of the test and 2.5 hours later. For left hand there is not

statistical evidence that shows how force decrease in function of time.

For hand force behavior related to day week, due to more than 90% of people are right-handed,

the expected force behavior is that on Monday are the greater averages while on Friday should be

the smaller averages. Table 12 shows that there is not any significative difference on right hand

force average. For left hand force average, respect to Monday is valid a decreasing force behavior

but statistically is valid only to Friday, on Tuesday the difference on average is only respect to

Friday. The other days remain the same.

As a final conclusion on this research the findings is that force has not a decreasing behavior due

to hours or days, it makes necessary to increase the number of measurements and run a test for

the thumb force.

This fact, no decreasing force behavior should be not assumed as a fatigue free operations, while

data were collected people says how at the end of the day they are with symptoms of pain and

numbness on fingers, wrist, shoulder, neck and low back. Highly repetitive operations may have

not an effect on force but that does not means that is an easy job.

In maquilas, there is a lot of situations that should be improved, beyond manufacturing and quality

is the human being, it is not only manpower, they are people and deserve a good place to

workon.

References Bernard, B. (1997). “Musculoskeletal Disorders and Workplace Factors; A Critical Review of Epidemiologic Evidence for Work-Related Musculoskeletal Disorders of the Neck, Upper Extremity, and Low Back”.Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health (NIOSH).



Colombini, D. (1998) 'An observational method for classifying exposure to repetitive movements of the upper limbs', Ergonomics, 41:9, 1261 – 1289. McAtamney, L. Corlet, N., (1973).“RULA; A survey method for the investigation of work-related upper limb disorders”. Applied Ergonomics; 24(2), 91-99. Muggleton, J. M., Allen, R. and Chappell, P. H.,(1999.) “Hand and arm injuries associated with repetitive manual work in industry: a review of disorders, risk factors and preventive measures”, Ergonomics, 42:5, 714 – 739. Keyserling, W. M., Stetson, D. S., Silverstein, B. A. and Brouwer, M. L. (1993) “A checklist for evaluating ergonomic risk factors associated with upper extremity cumulative trauma disorders”, Ergonomics, 36:7, 807 – 831.



ENVIRONMENTAL CONDITIONS VERIFICATION IN FACILITIES DESIGNED FOR NEW DEVELOPED PRE-SCHOOL LEVEL BUILDINGS IN THE

EDUCATIONAL SECTOR IN HERMOSILLO, SONORA DURING 2007-2008.

Francis María Quintero Díaz1, Manuel Sandoval Delgado1

1Departamento de Investigación y Posgrado Instituto Tecnológico de Hermosillo.

Ave. Tecnológico y Periférico Poniente S/N Colonia Sahuaro. Hermosillo, Sonora 83170

Corresponding author’s e-mail: [email protected], [email protected]

RESUMEN: Alrededor de todo el mundo, en el seno de toda clase de comunidades, con

independencia de condiciones económicas, u otras características físicas, existen escuelas en

condiciones precarias que se constituyen en barreras, a veces infranqueables, para que tanto los

estudiantes, como profesores y personal técnico y administrativo desarrollen sus actividades

normales dentro de los planteles con éxito. Tales condiciones pueden ser los niveles de ruido,

iluminación, temperatura y ventilación a los que están expuestos diariamente, es por eso que

hace dos años en la ciudad de Hermosillo sonora se empezaron a construir escuelas de nivel

preescolar diseñadas para que estas condiciones no afecten las actividades de las personas que

laboran en ellas.

El propósito de esta investigación es realizar un estudio comparativo entre la normatividad

correspondiente que rige el diseño y construcción del salón de clases donde laboran los niños y

el personal de las instalaciones de los edificios de nueva creación del nivel preescolar en el

sector educativo, en cuanto a medio ambiente se refiere; tales como ruido, iluminación y

temperatura, con los parámetros realmente encontrados en dichas instalaciones.

ABSTRACT: Around the world, within all kind of communities, regardless of the economic

condition or any other physical characteristic there are schools in such poor conditions that create,

sometimes insurmountable, barriers for students, teachers, as well as technical and administrative

staff to successfully develop their diary activities within school. Such conditions are related with:

noise level, lighting, temperature and ventilation which users are daily exposed to. As a response

to this situation, the pre-school level facilities that were designed so that the environmental



conditions could not affect the daily activities of their users, started to be constructed two years

ago in Hermosillo Sonora.

The aim of this research is compare the corresponding regulations ruling the design and

construction of classroom where children work and the personnel of pre-school level new facilities

in the educational sector in terms of environment such as: noise, light and temperature with

parameters actually found in these facilities.

1. INTRODUCTION

From the very moment of our birth we find ourselves immerse in a physical environment essential

for life; however, if that environment degrades, it might become an enemy of our health that would

chase us until the end (González, 1990).

According to the Instituto de Infraestructura Física Educativa (INIFED) (Institute of Educational

Physical Infrastructure), the classroom is where children and young people can reach through

knowledge a great number of better opportunities; therefore, it is necessary that all Mexican

students have access to quality education and schools that inspire and motivate the learning

(INIFED, 2008).

2. OBJECTIVE

Decide if the design of facilities for new developed pre-school level buildings in the educational

sector meets criteria established by the official standards regarding the design of the working

environment (noise, lighting, temperature and ventilation).

3. METHODOLOGY

The methodology carried out in this research is accordance with the Official Standards ruling the

design of working environment, such as:

3.1 Federal Regulation of Security, Hygiene, and Working Environment.



This regulation establishes the necessary measures to prevent accidents and illness of work,

trying to get the work done under safe, health and appropriate environmental conditions for

workers, in accordance with the Federal Labor Law and the International Trade held and ratified

by the United Mexican States related to these matters (Federal Regulation of Security, Hygiene,

and Working Environment), (1997)

3.2 Mexican Official Standards.

3.2.1 Mexican Official Standard NOM-011-STPS-2001, security and health conditions in

workplaces where noise is produced.

Data collected in Appendix B evaluation of the level of exposure to noise tells the following:

To evaluate noise in a permanent workplace the previous rule recommends that measuring spot

must be located in the place the worker usually takes (in this particular case, the child) otherwise,

as close as possible to it without hinder his/her work. In the same way, when a person works

seated, the microphone has to be placed at the workers head average level. Measurements were

taken as recommended.

Measurements were taken to the following conditions:

Children singing.

Children performing current activities (NOM-011-STPS-2001), (1994).

3.2.2 Mexican Official Standard NOM-015-STPS-1994, regarding to the labor exposure of high or

low thermal conditions in workplaces.

This rule makes some recommendations to take measurements, among them:

The position of the measuring spots depends on needs and characteristic of each area

and/or workplace. In this case, measurements were taken in the classroom central spot.

The height of the measurement equipment was set in accordance with the height of the

children’s work area (table): 60 cm.



The evaluation must be made at least three times during the 8 hour working day. Since

children work day lasts 3 hours, it was decided to take measurements every hour, starting

from the time they get in until the time they get of (NOM-015-STPS-1994), (1994).

3.2.3 The Mexican Official Standard NOM-025-STPS-1999, lighting conditions in workplaces.

The following activities were carried out according to law recommendations mentioned before:

Workplace reconnaissance.

Since sunlight and electric light are used, both conditions’ measurements were taken. For

the electric light, lamps were turned on 20 minutes before.

Measurement spots were set in accordance with the working area by the following formula:

Where:

Working area index/rate.

Working area dimensions (length and width) in meters.

Lamps height regarding the working surface, in meters.

In this case:

The number above is placed in the following table:

Table 1. Proportion between the working area index and the number of measurement areas

Index of area

Minimum number of areas to be evaluated

Number of areas to be considered by the limitation

4 6 9 12



16 20 25 30

Therefore, 9 areas were evaluated. Once the measurements were obtained, the % of Reflection

Factor was calculated (to compare information later on) by the following method:

Measurement spots must be the same as those set in the previous item.

Calculation of the surface’s reflection factor:

1. A first measurement (E1) is taken, with the luxmeter’s photocell facing the surface, at 10

cm ± 2 cm distance, until the reading remains constant;

2. In order to measure the incident light, the second measurement (E2) is taken with the

photocell on the surface facing the opposite direction;

3. The surface Reflection Factor (Kf ) is calculated with the following equation:

(NOM-025-STPS-1999), (1999).

3.3 Instituto Nacional de la Infraestructura Física Educativa (INIFED). (Institute of Educational

Physical Infrastructure) The INIFED (2009) is the organization of the Federal Public Administration

responsible for the construction, restoration, maintenance and equipment of the national

educational physical infrastructure. It is important to mention that this institution does not say how

to take measurements, it only provides parameters that must be met regarding the working

environment; in addition to that it is based on the Mexican Official Standards.

4. RESULTS

Results shown below were collected in three classrooms during summer time.

4.1 Noise:

(2)



Table 2. Results of the Noise Factor’s (Lux) measurements. 1 2 3 Max Min Max Min Max Min

Children singing 89 47.5 85 51.3 86.4 45.6

Current activity 87.5 43.8 75.6 42.6 8 43.8 4.2 Temperature.

Table 3. Result of the Temperature Factor’s (Lux) measurements.

09:30 a.m.

1 2 3 Min 24.5 22.8 24.7Average 25.9 24.8 26.6Max 27.3 26.7 28.4

10:30 a.m.Min 28.9 28.4 29.8Average 29.5 29 29.7Max 30.2 29.7 29.7

11:30 a.m.Min 33.3 32.4 34.2Average 33.7 33.2 34.7Max 34.1 34 35.2

4.3 Lighting.

Table 4. Results of the Lighting Factor’s measurements, classroom 1.

LIGHTING (Lux) % REFLECTION FACTOR

Natural Lighting Electric Lighting Natural Lighting

Electric Lighting

Max Min Max Min Max Min Max Min Classroom Measurement #1 264.7 233.3 640 590 40.0075 30.7758 28.5762 27.5937Measurement #2 534 486 748 716 26.7790 27.8600 29.2647 28.3798Measurement #3 547 478 947 756 27.7879 30.9205 29.2647 28.8359Measurement #4 912 892 1285 1234 24.4517 24.0022 25.0405 24.7081Measurement #5 1113 1070 1389 1373 29.3800 22.6168 26.3570 24.4136Measurement #6 1181 1139 1439 1434 22.5402 22.8709 23.3009 21.9456Measurement #7 494 398 918 891 30.6072 26.4070 27.1132 23.1986Measurement # 8 632 483 980 726 30.8723 26.2456 25.5478 21.6591






Electric Lighting

Max Min Max Min Max Min Max Min Classroom Measurement #1 318 299 525 506 32.7044 33.7792 36.1904 36.5612Measurement #2 347 323 614 607 39.7694 41.7956 32.8990 32.1252Measurement #3 735 712 651 636 27.4829 26.1235 37.6344 27.9874Measurement #4 668 654 812 803 38.4730 36.5443 36.8226 33.7484Measurement #5 597 557 955 814 38.3584 39.1382 42.1989 39.9262Measurement #6 606 591 787 761 40.4290 32.4873 39.7712 40.3416Measurement #7 395 347 758 682 40.5063 44.6685 37.2031 39.8826Measurement # 8 465 446 872 832 38.9247 39.4618 37.2706 30.8894




Electric Lighting

Max Min Max Min Max Min Max Min Classroom Measurement #1 290 276 535 518 35.5172 36.5942 35.3271 35.9073Measurement #2 325 305 624 607 39.3846 43.9344 32.0512 32.1252Measurement #3 680 677 635 628 29.5588 28.0649 36.2204 27.0700Measurement #4 670 655 821 807 29.5522 28.5496 35.3227 31.7224Measurement #5 620 598 859 851 28.8709 26.7558 46.5657 38.0728Measurement #6 586 580 789 771 29.0102 28.2758 39.5437 39.6887Measurement #7 405 398 759 682 35.3086 35.4271 36.8906 39.8826Measurement # 8 486 476 921 897 26.3374 25.8403 35.1791 28.6510



4.4 Ventilation.

Figure 1. Windows view.

5. CONCLUSIONS.

The Mexican Official Standard number 011 concerning to noise indicates that a hazardous situation occurs when dBs number surpasses 90. In this case the noise did not exceed the limit, at least not when children were there. The INIFED states that the advisable environmental conditions for working in a comfortable area, in the case of classrooms, are 18 to 25 Celsius, noticing that this condition is not fulfilled since most measurement exceeded 25 Celsius. According to the prevoiusly analized NOM 025, the lowest lighting level must be 300 (lux) for older people. As is noticed in the prevoius measurements, this parameter is not met, so that we can infer that light is not well distributed. The reflection on the furniture where kids work was another important issue that was evaluated and according to INIFED standards, the reflection highest value should be 50%, and as it is noticed in the previous measurements, does not exceed such level.



6. REFERENCES.

González Gallego Santiago (1990). La ergonomía y el ordenador. Primera edición, Editorial Marcombo, S. A. Barcelona España. Instituto Nacional de la Infraestructura Física Educativa (INIFED), (2008). http://www.inifed.gob.mx/templates/objetivos.asp. Página visitada el 13 de agosto de 2009. INIFED, (2009). Volumen 3. Habitabilidad y funcionamiento. Tomo I. Diseño Arquitectónico. http://www.inifed.gob.mx/templates/normas%20t%C3%A9cnicas.asp. Página visitada el 12 de marzo de 2009. (NOM-011-STPS-2001), (1994). Publicada en el Diario Oficial de la Federación el 06 de julio de 1994. México, D.F. http://www.stps.gob.mx/DGSST/normatividad/noms/Nom-011.pdf. Recopilada en la página el 6 de mayo de 2009. (NOM-015-STPS-1994), (1994). Publicada en el Diario Oficial de la Federación el 19 de julio de 1993. México D.F. http://www.stps.gob.mx/DGSST/normatividad/noms/NOM-015.pdf. Recopilada en pagina el 6 de mayo de 2009. (NOM-025-STPS-1999), (1999). Publicada en el Diario Oficial de la Federación el 27 de septiembre de 2005, México, D.F. http://www.stps.gob.mx/DGSST/normatividad/noms/Nom-025.pdf. Recopilada en la página el 6 de mayo de 2009. (Reglamento Federal de seguridad, higiene y medio ambiente de trabajo), (1997). Publicado en el Diario Oficial de la Federación el 21 de enero de 1997. México, D.F. http://www.stps.gob.mx/marcojuridico/vinculos_juridico/reglamentos_marco/r_seguridad.pdf. Recopilada en la página el 6 de mayo de 2009.



ADVANTAGES OF THE ORTHOGONAL ARRANGEMENTS OF THE METHOD TAGUCHI IN THE DESIGN OF EXPERIMENTS IN ERGONOMIC

Alois Fabiani-Bello1, Humberto García-Castellanos2, and Rosa M. Reyes2

1Programa de Doctorado en Ciencias de la Ingeniería (DOCI) Universidad Autónoma de Ciudad Juárez

Ave. Del Charro 450N, C.P. 32190 Cd. Juárez, Chihuahua, México.

e-mail: [email protected]

2Departamento de Ingeniería Industrial Instituto Tecnológico de Ciudad Juárez

Av. Tecnológico Nro. 1340 Cd. Juárez, Chihuahua, México.

Resumen: Los métodos estadísticos basados en la función Chi-Cuadrada son frecuentemente

utilizados por los ergónomos y estas técnicas por su naturaleza no paramétrica usualmente

requieren de una gran cantidad de datos experimentales con el correspondiente uso de recursos

y contienen una importante dosis de subjetividad basada en la experiencia del experimentador.

Las metodologías de experimentación podrían ser más rápidas y más económicas para tomar

decisiones con la mejor información estadística posible utilizando técnicas apropiadas del Diseño

de Experimentos. El autor Fabiani-Bello et.al. (Conergo, 2008) expone un método conceptual

basado en simulación Monte Carlo y experimentos sin réplicas que fueron utilizados para planear

la experimentación en ergonomía al categorizar la fatiga visual o astenopia. En base a la misma

línea de trabajo Reyes-Martínez et.al. (Conergo, 2009) muestra los primeros resultados del

método caracterizando la fatiga visual según publicaciones recientes dando a lugar la

identificación clara de los factores que influyen en la astenopia y pone a prueba los métodos

estadísticos tradicionales. Después de dos años de investigar las ventajas y limitaciones del

método Taguchi en varias aplicaciones experimentales se propone en este artículo el método

validado del diseño experimental basado en arreglos ortogonales del Método Taguchi que podría

ser usado en los experimentos de la ergonomía donde, según el ajuste de niveles factoriales de

diseño, es posible medir el impacto de estos arreglos en alguna variable de interés retomando las

conclusiones obtenidas hasta la fecha sobre el tema.

Palabras Clave: Metodo Taguchi, Arreglos Ortogonales, Diseño de Experimentos



Abstract: The statistical methods based on the Chi-square of test (2χ ) are much used by the

ergonomics and these need from a significant and big size of the sample with the corresponding

use of resources and it contains an important dose of the subjectivity. Due to the cost of

opportunity the methodologies must be more rapid in the treatment of the information, must be

more economic and to take decisions with the best statistical information. Fabiani (2008) proposes

a conceptual method based on simulation Monte Carlo that was used to plan the experimentation

in ergonomics to the categorizer the visual fatigue. Based on the same line of work Reyes-

Martínez et.al. (2009) it shows the first results of the method characterizing the visual fatigue as

recent publications. The authoress identifies in a clear way the factors that influence the astenopia

and it puts to test the statistical traditional methods. After two years of investigating the

advantages and limitations of the method Taguchi in several experimental applications there is

proposed in this article the validated method of the experimental design based on orthogonal

arrangements of the Method Taguchi. The method that might be used in the experiments of the

ergonomics where according to the level adjustment factorials of design it is possible to measure

the impact of these arrangements in some variable of interest recapturing the conclusions

obtained up to the date on the topic.

.

Key words: Taguchi Methods, Orthogonal Array, Experimental Design.

1. INTRODUCTION

The visual system is one of the principal organs of the human being since 80% of the emotions

are perceived across the sight. The sciences that study the system of the sight begin to be

interested in the labor matters at the end of the XIXth century turning into a more and more

specializing professional activity and into a world more industrialized (Reyes-Martinez et.al, 2005).

The new places and forms of work, the beginning of the automation and the systems of industrial

production based on the competition for the quality (De la Vara, 2002) give place to a symptom

that starts attracting attention of some specialists and especially of the companies because they

realize that sometimes his workpeople can suffer a serious damage: The most common

complaint, as for visual inconveniences, is vaguely described as " tired sight ". Other symptoms



indicate blurry sight or the difficulty to focus objects closely or of far, the unsteady vision and the

double image. The headache is the most common general symptom, but not always it must be

related to the visual weariness. Specifically, the symptoms of weariness or visual fatigue can be

aggravated by diverse factors. On the other hand, the sight deteriorates gradually in the adults

and this decrease is marked especially between 30 and 50 years (Reyes-Martinez et.al. 2005).

The system of vision of the human being perceives the reality across the eyes, by means of these

the brain perceives the signs and processes them; these signs are received in an environment

with lighting, the color, the moisture between others they generate changeability in the system of

vision. With the time, the visual system deteriorates for the rhythm of industrial repetitive work.

The signs of Visual Fatigue as the frequency of blinking might be abstracted as exits of the effort

of the system to face his fatigue (Okada, 2002).

The relation between the Engineering of Quality and the Ergonomics is real because both want to

improve the yield of a system, in the first case the experimentation has an important role in new

products design, in developing manufacturing processes and in the improvement of processes

and in the second case the characterization of factors so that the health is not damaged in the

persons. With regard to the experimentation one of the most used methodologies and recognized

for its efficiency is the one proposed by Dr. Genichi Taguchi. In Quality Engineering, it is

mandatory to select the operative levels of the control factors that affect to critical characteristic of

quality, and then abstracting the Visual Fatigue as a "characteristic of quality" it is necessary to

minimize it.

2. METHODOLOGY FOR SELECTING THE PARAMETERS

To understand and to talk about the interaction between the persons and his environment implies

respecting many methodological, statistical restrictions and even of anthropology; the experience

says to us that these models that to the moment can be only theoretical, help to understand the

behavior of the system more they do not allow to manipulate it. Our methodology is designed only

for knowledge of relations cause - effect between the factors and the variable of exit of the



system. In this sense the method Taguchi for the prophecy of the output variable in the process is

most adapted for our case; the process can be divided into five stages summarized in Table 1.

Table 1. Stages for the experimental design

No.

Stage Activity Content

1 Preparation

1.1 Determine the experimental objective and target-

characteristic values.

1.2 Determine whether it is worthwhile to carry out the

experiment under the current conditions.

2. Determination of

factors and levels

2.1 List all factors that relate to the objective (more

than 50) with a Focus Group

2.2 Select and determine factors and levels to be

tested.

3. Assignment 3.1 Assign factors and levels to the orthogonal array.

4. Experiment

4.1 Eliminate the obstacles hindering the experiment.

4.2 To continued the process of randomized

experimentation generating only an experimental reply.

4.3 With the simulation Monte Carlo all the possible

outputs will be obtained

5. Data analysis

5.1 To construct the correlogram and to interpret the

coefficient of Pearson to characterize the incidental

factors.

5.3 Determine the optimum condition and to confirm

them with the existing norms in the legal environment

of Occupational Health.

The sequence of the methodology and the recommendations of his application are based on the

interpretation that the Dr. Teuro Mori does to the method Taguchi in his work titled originally "

Taguchi Mesoddo or tsukatta yasashii shinjikken keikakuho nyumon " (1946).



2.1. Experimental Design Application: First and Second Stage – Preparation and Determination of factors y levels.

The target of the experimentation applied to the ergonomics will have to maximize or minimize an

effect and it is clear that to maximize a variable sometimes implies minimizing his complement.

The clear identification of the variable of exit of the interaction between the man and the system is

important. The scope of the experiment is to know the factors that they affect in the awaited result

and to arrange them according to his contribution to the changeability of the system.

At first more than 50 potential factors must be put in a list and to obtain this number it is necessary

to ask medical specialists that have worked with the topic, it is key to confirm points of view of the

participants and to assume a position based on the nature of the industry at which one is

employed. The information will be better if it is investigated in the arbitrated publications,

catalogues and tests previous.

Another key of the ergonomic experimental process is to classify the factors and to define the

levels of the experimentation, for this activity it is necessary to identify clearly the class of factor

(Mori, 1946). As well as to classify to the factors in the function to his relation with the studied

effect and to avoid the strong interaction between them, this is important for the complexity of the

system in study. We cannot experiment with all the factors but the target here is to consider all the

important factors. In this stage of the experimentation the people can have different opinions, in

such a situation, we do not have to classify rigorously the factors and that's why we make use of

orthogonal series to confirm his effect.

After defining the factors, we determine his levels. The number of levels should be two, three, or

four. The use of three levels is recommended in particular (G.Taguchi, 1986). The works of the

theoretical investigation demonstrated that this type of level determination they generate

quadratic’s terms in the model (Fabiani-Bello, 2008).



2.2. Experimental Design Application: Third Stage – Assignment.

It is known that the most usual criterion to select the experimental design is the reduction of the

variance of the regression coefficients. The key element to select a design that diminishes the

variance is the orthogonality concept used by Taguchi in experimental designs. In fact, the

complete factorial designs of two levels and the fractions of resolution III are orthogonal.

In the ergonomic experimentation is possible to separate main effects and interactions using

either of the following methods: (1) assign the main effect to the points to the linear graph

assuming that interactions between three factors does not exist; (2) use a special orthogonal array

where interactions confound equally with every level of the main effects. The first method uses the

columns corresponding to the points on the linear graph en orthogonal arrays 932168 ,,, LLLL

and 27L . For the second method 1812 , LL and 36L orthogonal arrays are used which are of practical

use in the industry for their effectiveness and reduction of costs (Wu, 1992).

If we cannot anticipate possible interactions between factors, we can obtain quite a lot of

information from past experience. But, if we cannot anticipate interactions, we can take any of the

following approaches: (1) Assign the interaction between two factors. (2) Use orthogonal arrays

1812 , LL or 36L that does not generate interaction information. (3)Ignore interactions when you

assign factors.

For experiments in ergonomics it is of interest principally to know the principal effects of factors,

from what the second option is most recommended since it uses three levels and does not need

to stop in the study of interactions that might be subjective in this stage of the process although

the ability to anticipate is a part of technological know-how (G.Taguchi, 1986). For this reason the

Taguchi methods for the case of study have been programmed in spreadsheets because these

allow flexibility of programming for this type of algorithms. In fact, it contains statistical tools.



2.3. Experimental Design Application: Fourth Stage – Experimentation. In the industry the resources are in general limited it is very probable that the number of

experiments is limited to the available budget, in this case a design factorial finished and with only

one experimental response can be used, nevertheless the principal effects can contain an error

generated by the external noise (Montgomery, 2006). The principal disability of this method

consists of the fact that is known that to certain number of factors this process is expensive.

The methodology Taguchi usually guarantees less experimental tests and makes use of the big

advantage of the orthogonal arrangements then to construct a reliable model to know the value of

the average of the process with the following equation:

)(...)()(ˆ yNyByAyy srk −++−+−+= (1)

Where:

y = theoretical average of the process.

y = real average of the process.

NBA ,..., Are the experimental factors.

srk ,..., Are the levels of the experimental factors.

In this way, the Monte Carlo method is used to simulate all possible iterations in a predictive

model of values of the average. This means that in our methodology there will be randomized the

order of the capture of information to only one reply and later to obtain the theoretical model of the

average based on the contribution of the principal effects, with the equation (1) there will be

generated all the possible values of the average making use of the Simulation Monte Carlo. In

studies realized with regard to the MAPE of the theoretical model his value is usually 4 %

(Fabiani, 2008).

With regard to the person chosen for the experiment, the International Organization of the Work

tells that the "average" worker does not exist in the reality, but based on the requests of the



industrial work for which is experienced it is known that the profile of the person who executes the

task and the Ergonomist jointly with the Engineer can suggest the conditions of an operator

qualified for the position, this is that person who has necessary fitness, with required intelligence

and instruction and who has acquired the workmanship and necessary knowledge to carry out the

current work as norms of quality, quantity, health and safety (OIT, 1986).

2.4 Application of experimental Design: Fifth Stage – Analysis of the information.

Changing the levels of the factors, it is possible to know the interrelation between variables of

entry and variables of exit to the system, the distributions of frequency for every variable and to

the simulation of the experiment. Finally, the simulated population is validated comparing the

levels of interrelation between variables and the percentage of obtained contribution of the

ANOVA.

The method allows to obtain a graphic report of different iterations to select the best combination

of parameters. The relationship between the response variable and the independent variables is

obtained based on the experience in previous investigations, which has found a narrow relation

between coefficient of Pearson with the ANOVA (García-Castellanos and Fabiani-Bello, 2007).

The following step is to verify the law with regard to the important factors in the response of the

model and if norms do not exist on this matter it is necessary to choose the most appropriate

levels of operation that maximize or minimize the response.

3. CONCLUSIONS

It has been demonstrated that Taguchi methods are an important tool. Due to its simplicity, the

use of these methods has become frequent in different areas and different productive processes.

After the statistical experimentation, the Taguchi methodology allows to predict the performance of

a process by means. The implementation of this methodology is simple and practical and it does

not require of advanced statistical knowledge. Also, the validation of the method presented here

could be by means of a case of study.



4. REFERENCES

Ross, Phillip J. (1996). Taguchi Techniques for Quality Engineering. McGraw-Hill Co., United

States of America.

Wu, Yuin, and Wu Alan (1997) Diseño Robusto utilizando los métodos Taguchi. Díaz de Santos

S.A. Ed, Madrid, Spain.

Suart P. Glen (1993), Taguchi Methods: a hands-on approach Addison-Wesley Co, Inc., United

States of America.

American Supplier Institute, Inc. (1987) Introduction to Quality Engineering: Course Manual.

Center for Taguchi Methods, United States of America.

Terou Mori (1946). The New Experimental Design, ASI Press, United States of America.

Nelson Rodríguez (1999), Aplicación del Diseño de Experimentos para determinar el máximo

peso aceptable en el manejo manual de materiales, Departamento de Ingeniería

Industrial, Universidad de los Andes, Colombia.

Tames Gonzalez S, Mart'nez-Alcántara S., Use of personal computers and health damages in

newspaper industry workers. Salud Publica Mex 1993;35:177-185, Mexico.

Rosa María Reyes Martínez M.C et al. (2005), Ergoftalmología: Análisis de los Factores que

Inciden Astenopía de los Trabajadores de Inspección Visual Industria Electrónica de

Ciudad Juárez, Memorias del VII Congreso Internacional de Ergonomía, Nuevo León,

México, 3 al 5 de noviembre del 2005.

Akira Okada (2001), Medición de la "Fatiga Visual", Universidad de Osaka, Panasonic Services

(Central), Sancho de Ávila, 54, 1ª planta, Barcelona, Spain.

Guillermo Martínez de la Teja, Diseño ergonómico para estaciones de trabajo con

computadoras, Memorias del II Congreso Internacional de Ergonomía, Ciudad Juárez,

México, Mayo 2000.

Victor García-Castellanos, Alois C. Fabiani-Bello, and Humberto Hijar-Rivera (2007), A

Computing Approach Based On The Taguchi Methods To Optimize The Selection Of

Factors For The Nominal-The-Best Characteristics, Proceedings Of The 12th Annual,

International Conference On Industrial Engineering, Theory, Applications and Practice,

Cancun, Mexico, November 4-7, 2007.



Fabiani-Bello, Alois (2008), Aportación Metodológica al Diseño de Productos Robustos según la

filosofía de Genichi Taguchi, División de Estudios de Posgrado e Investigación, Instituto

Tecnológico de Ciudad Juárez, México.

Reyes-Martinez, Rosa (2009), Categorization of factors causing asthenopia en research

professors at the itcj by Reading wit vdt: a shared experience, SEMAC 2009, pp. 154-166



ACADEMIC ASSAYS FOR ERGONOMICS. LDI Zoe Madai Cruz Purata1, LDI María del Sagrario Medina Rodríguez2, Arq. Julio Gerardo

Lorenzo Palomera3

1Coordinadora de la Carrera de Diseño de Interiores. 2 3 Facultad de Arquitectura, Diseño y Urbanismo.

Universidad Autónoma de Tamaulipas. Campus Tampico – Madero.

[email protected] RESUMEN. Se presentan dos ensayos realizados en la Facultad de Arquitectura, Diseño y

Urbanismo (FADU). En el contexto interactivo de las carreras de Arquitectura y Diseño de

Interiores, se desarrolló un estudio básico del ambiente acústico que incide en el aula, por otro

lado se hace una aproximación de análisis antropométrico de nuevo mobiliario para los talleres de

diseño.

El estudio acústico tiene como finalidad que el alumno se sensibilice con la noción ergonómica y

se familiarice con herramientas elementales, como el decibelímetro, para diagnosticar y controlar

el ambiente sonoro, ahora a nivel escolar, pensando en su aplicación en entornos reales. Se

sigue un método de medición simple, en una secuencia predeterminada de espacios. Se

obtienen indicadores no del todo adecuados para un óptimo ambiente de aprendizaje.

El diagnóstico de mobiliario se aplica en un juego de restiradores “gemelos”, con dimensiones

establecidas por el fabricante. Se aplica una técnica de observación de postura relacionada con

el alcance y la holgura, de usuarios en interacción con el mueble, de una muestra de la población

estudiantil en la FADU. Los resultados llevan a la reflexión de cómo la aparente comodidad puede

ser realmente una lastimosa costumbre, a ser cultivada en los años de carrera universitaria.

Palabras clave: Interiorismo. Bienestar. Ergonomía. Acústica. Antropometría.

ABSTRACT. We present two tests conducted at the Faculty of Architecture, Design and Urbanism

(FADU). In the interactive context of careers in Architecture and Interior Design, it was developed



a basic study of acoustic environment impact in the classroom. Then it was applied an simple

anthropometric analysis on new design workshops furniture.

The acoustic study aim was to sensitize students about ergonomic notion and become familiar

with basic tools such as decibelímetro, diagnose and control the sound environment, now at

school, thinking about its application in real environments. It was followed a simple measurement

method, in a predetermined sequence of spaces. Obtained indicators were not entirely

appropriate for optimum learning environment.

The diagnosis of furniture applies drawing board in a game of "twins", with dimensions specified

by the manufacturer. It was applied an observational technique of scope and slack related

posture. User - furniture interaction was observed of a sample of the student population. The

results lead to the reflection of how the apparent comfort can be really a pitiful habit to be

cultivated in the years of college.

Keywords: Interiorism. Welfare. Ergonomics. Acoustics. Anthropometry.

PROLOGUE.

We present two academic assays conducted at the Faculty of Architecture, Design and Urbanism

(FADU)

In the interactive context of Architecture and Interior Design careers, it was developed a basic

study of acoustic environment impact in the classroom, besides an approximation of

anthropometric analysis of new furniture for the design workshops. Both exercises are strategies

to reduce the gap between design activities and ergonomics, as well as linking quality as a daily

practice.

Ergonomics as inherent quality factor should be fully present in the field of design. In practice it is

found that various educational trends, not necessarily provide consumers welfare in their models.



The environmental experience as part of the learning process is student-way reference in its

professional life. Hence the need to reorient educational objectives in design.

Exercise 1: Acoustic study of a learning environment.

1.1. INTRODUCTION. Conceptual Framework.

As part of the exercise was revised conceptual framework based on Mapfre Foundation

Ergonomics Handbook

Ergonomics deals with the study of any physical environment from three sources: the

measurable factors of the environment that are susceptible to modification, the physiological

effects produced by these factors and also how the employee feels that environment. The sound

from the physical point of view is a mechanical vibration transmitted through the air, capable of

being perceived by the auditory organ.

1.1.1. Sound effects in people.

The sound effects can occur in people from three aspects: perception, extra-auditory effects,

auditory effects.

Perception.

The inner ear acts as a transducer, transforming the physical signal (mechanical) in

physiological signal (nervous), which is transmitted through the auditory nerve to auditory cortex,

which produces the integration and interpretation of those signals.

Extra-auditory effects.

The fact that noise can cause physiological reactions of "stress" seems widely accepted, but has



not yet established that these reactions can produce pathological effects. However, an analysis of

more than one hundred relevant literature indicates that the most important are:

Modification of the cardiovascular system: blood and heart rate.

Influence on muscle tone.

Digestive disorders.

Visual function alterations.

Alterations on metabolism.

Auditory effects.

The auditory effects are: injury to the ear and difficulty in language comprehension. For the scope

of the study, was only considered the first. In an environment where understanding of the word

difficult, is very likely that there are difficulties that will lead to discomfort for the worker and work

impairment. The spoken word is a sonic element with high information content, so the process of

perception is determined by various acoustic phenomena and the special interpretation of the

message conveyed by the word.

1.1.2. Acoustic comfort.

The type of noise that bothers more in an office environment, is produced by the talks. Each

type of activity will be treated differently. Can be generalized in terms of noise levels, noise in

manual labor began to be troublesome from 80-90 dB, matching the levels from which they can

and assume the risk of deafness.

1.1.3. Effectiveness.

Noise can alter a person's efficiency decreased performance and increased errors and

accidents. Rates were determined for intellectual work discomfort, for example Beranek (1969)

and Wisner, setting graphic curves correlated noise level in decibels and octaves center

frequencies. The scope of this assay was limited to a simple sequence of measurement, but

checking on the charts for better understanding by students. (Mapfre Ergonomics Manual)



1.2. OBJECTIVES.

Sensitize Interior Design students on the need to adapt the environmental conditions for human

activity, in this case, learning. To learn the use of simple measuring sound tools, to diagnose and

monitor a sound environment.

1.3. METHOD.

It was simplified to an academic exercise, the procedure established in the Mexican Official Norm

for the security about noise sources. So, establishing six significant locations in the FADU

campus, the sound pressure was measured. It was used a type 1 sound level meter, with a range

of 50 to 120 dB, for capturing only the sound pressure.

The group of 15 students made measurements in the selected areas thus obtained 90

different indicators. For practical reasons the group was subdivided into two: seven people were

devoted to three sites, and 8 to the other three areas. It was registered measurements taken in

each area for a period of five minutes, for each student.

1.4. RESULTS.

The entire series averages were obtained, performing a table summarizing the average of the

measurements (see Table 1). The teacher previously presented in the classroom as an

introduction to the exercise and how to do it, including a concise explanation of the sound level

meter use.

Table 1. Sound Pressure measurementes.

Site. Sound Pressure. dB

Exterior environment (far away site) 40

Class room 67

Library. 64



Laboratories (under construction) 71

Patio. 66

Cafeteria. 73

We compare the results:

a) With the recommended values in the corresponding official Mexican standard, which is 68 dB

from 6:00 to 22:00 and 65 dB from 22:00 to 6:00.

b) With the levels recommended by the ILO (OIT).

c) It was showed the graph produced by Beranek. Although not conducted a detailed acoustic

study to develop positions on the curves plotted, the models allow students to view individual

cases.

It is noted that approximately 55-90 dB levels for intellectual labor, it is extremely painful,

depending on sound frequency.

Table 2. Sound Pressure levels. OIT (ILO).

Effect on humans Sound Level dB. Sound source.

Extremely harmful.

140 Jet engine unit.

130 Riveter.

120 Pain threshold. Propeller aircraft.

Harmful.

110

Rock drill.

Chainsaw.

Metalworking shop.

100 Truck.

90

dangerous. 80 Busy street (car traffic)

Prevents talk. 70 Passenger car.

60 Normal conversation.



Irritant. 50 Talk quietly.

40 Music played on radio at low

volume.

30 Whispers.

20 City quiet floor.

10 Whisper of leaves

(vegetation).

0 Hearing threshold.

1.5. CONCLUSIONS.

It was expressed by the group the distinction of sounds within the classroom and outside, the

habit of perceiving external sounds as part of the learning environment, like a sound

accompaniment. Especially noticed some discomfort because the dominant noise abroad, is to

talk out loud.

Regarding the Library, a combination of whispers, voices, noise from air conditioning

equipment, produce anxiety and stress in the interior. Inside the cafeteria, conversation is difficult

because of the noise.

It was found that the materials used in buildings are not insulated or sound-absorbing. They

are generally flat surfaces finished in painted cement, windows aluminum bearing. Also it was

noted the classrooms air conditioners, as sources of noise.

The exercise participants were sensitized on to consider ergonomics to achieve acoustic

comfort in the spaces.



2. ANALYSIS OF NEW DESIGN WORKSHOPS FUNITURE.

2.1. INTRODUCTION.

In Design learning, we consider the experience as a key factor. Since the products generated will

be used by users, which we seeks to satisfy. Considering as example the model of Kolb (1984),

the traditional tendency is to exercise the conceptualization phase mostly in institutions. Taking a

side step, we invited a group of students to think about their academic work. Leaving aside the

conceptualization only about ergonomics, was experienced and observed the use of furniture for

design: a drawing desk prototype.

2.2. OBJECTIVES.

The student through observation, conceptualization and experimentation known anthropometric

parameters.

2.3. METHOD.

Concepts were presented using anthropometry concepts and anthropometric tables, considering

the scope and parameters of clearance,



It was conducted a simple anthropometric prototype drawing board "Twins." Continued as a

methodology: analytical observation of the furniture in situ and photographs, analysis of simulated

activity in furniture-user interaction, considering heights from 1.65 to 1.83 meters, in both sexes.

The positions were static. It took anthropometric reference tables published by Prado-Ávila (2007).

Observations were made of the furniture itself and users interacting with the furniture. There were

registered users feelings about.

It was made a physical survey of the furniture. It consists of two drawing tables linked by a metal

structure made with angles of different caliber and length. Among these was placed additional

shelf. The seat is circular, wood, supported on a rotating structure, a wheel support flange at the

base, allows translation moves, subject to a pivot (see Figure 1). At first glance it seemed

interesting.

Figure 1. “Twins” Drawing Board Prototype

They were invited to use the furniture first requesting suit as they liked it. Later they went in static

postures leading to experience and visualize the scope and clearance parameters, comparing

dimensions between the object and the person.



2.4. RESULTS.

Discoveries:

The table surface measures 70 x 80 cm which is insufficient to work in a drawing paper sheet, in

addition, there is no support for the drawing tools on the table and they could slip. Other coating is

also recommended as this would prevent the tape off the ground especially because the climate

humidity.

It is needed an convenient adjustable board angle; it was fixed. Since the scope distances ratio

from the user's fingertips on the furniture, creates an awkward bend in the lower back and also

high tension in the shoulders and neck. Raise the height floor-edge of the table (0.91 mts.) would

help to correct posture, facilitating work with the spine erect. For 95th percentile person said he

felt comfortable until he was told to straighten the back (see Figure 2).

Figure 2. Working posture: "comfortable" and erect. Percentile 95.

It is suggested that in addition to the intermediate table support, useful for holding backpacks or

bags, adding a drawer along the front edge of the table in each module for drawing and painting

tools at hand. It is recommended to add a table with pen holders, whose support is articulated, at

least one of the vertical bars of the support desk, and free rotation adaptable to the scope of the

user. This little shelf complement the user's work when to laptop use is needed.



Regarding the seat, it was noted the absence of lumbar support (lower back), plus the hard, flat

surface is uncomfortable after a while of use, is proposed to be padded, in a broader measure

even for obese people, as default timber is still important to be configured curves of the buttocks

and knee. It would be advisable to consider a footrest support tube in the bank, and the swivel

seat is height adjustment screw. People in 5th percentile needed to rely on tip toes on the ground

(see Figure 3).

Figure 3. Sitting posture Percentile 5.

2.5. CONCLUSIONS.

Continuing the efforts to sensitize the academic population at the Faculty of Architecture, Design

and Urbanism of the UAT, to update the application of ergonomics, we believe these tests

successful. The training process needs to adapt to the dynamic professional. In the field of design,

experience is gained from learning in workshops and classrooms.

In the second exercise, underwent an apparent "comfort" in the use of furniture design from the

anthropometric point of view, and recognized awkward postures. The experience generated

improvement ideas.



5. REFERENCES.

Ávila Ch. R.- Prado L., L. – González M., L (2007). Dimensiones antropométricas. Población

Latinoamericana. Universidad de Guadalajara. Centro Universitario de Arte, Arquitectura y

Diseño. Centro de Investigaciones en Ergonomía. México.

Beranek, Leo L. (1969). Acústica. Editorial Hispanoamericana. Buenos Aires.

Fundación Mapfre (1997). Manual de Ergonomía. Editorial Mapfre. Madrd.

NORMA Oficial Mexicana NOM-081-ECOL-1994. Límites máximos permisibles de emisión de

ruido de las fuentes fijas y su método de medición.

http://www.sma.df.gob.mx/tsai/archivos/pdf/12nom-081-ecol-1994.pdf



ANALYSIS OF CORRELATION BETWEEN THE VARIABLES OF TEMPERATURE, STRENGTH AND CYCLES PER MINUTE TO

PERFORM HORIZONTAL REPETITIVE MOVEMENTS OF THE WRIST

Camargo Wilson Claudia1, 2, Rivera Valerio Abril A.1, Rubio Martinez Jesus R.1, de la Vega Bustillos Enrique J.3,

López Bonilla Oscar R.2, Olguín Tiznado Jesús E.1, 2, Báez López Yolanda A.1, 2

1 Department of Industrial Engineering - Engineering Faculty Ensenada.

Autonomous University of Baja California. Km. 103 Highway Tijuana-Ensenada S/N

Ensenada, Baja California. Zip code 22760 [email protected], [email protected], [email protected]

2 Division of Posgrade and Research MyDCI- Engineering Faculty Ensenada.

Autonomous University of Baja California. Km. 103 Highway Tijuana-Ensenada S/N Ensenada, Baja California. 22760

[email protected], [email protected], [email protected]

3 Division of Postgraduate Studies and Research Technological Institute of Hermosillo

Technological Avenue S/N Hermosillo, Sonora. 83170 [email protected]

RESUMEN. La necesidad de proteger a los trabajadores contra las causas que provocan tanto

enfermedades profesionales como accidentes de trabajo es una cuestión indudable. De ahí el

interés de analizar el comportamiento que tienen las variables de temperatura en el área de la

muñeca, la fuerza y los ciclos por minuto ello al llevar a cabo movimientos repetitivos horizontales

de la muñeca, los cuales son comúnmente encontrados en los lugares de trabajo. Objetivos:

Correlacionar las variables de temperatura, fuerza y cantidad de movimientos por minuto cuando

se trabaja con el movimiento repetitivo horizontal en el área de la muñeca. Delimitación del

problema: Se simuló la jornada laboral de ocho horas con dos operadores (hombre y mujer)

ejerciendo los movimientos horizontales, en las instalaciones de la Facultad de Ingeniería

Ensenada de la Universidad Autónoma de Baja California. Metodología: Se simuló la jornada

laboral con dos operadores ejerciendo los movimientos horizontales, para ello se realizó el

registro de la temperatura en el área de la muñeca derecha (termógrafo sensorial Sköll), la fuerza

del individuo (dinamómetro de torsión de muñeca Baseline) y los ciclos por minuto, los tres



registros mencionados anteriormente se realizaban cada diez minutos. Resultados: Los

resultados obtenidos fueron los siguientes: en el operador 1, se encontró correlación en los ciclos

por minuto contra temperatura y contra fuerza; además el máximo en: la temperatura fue

35.93°C, la fuerza 82 kg y los ciclos por minuto fue de 138 movimientos y el mínimo en: la

temperatura fue 28.11°C, la fuerza 36 kg y los ciclos por minuto fue de 93 movimientos; en el

operador 2 la correlación que se manifestó fue la de ciclos por minuto contra temperatura;

además el máximo en: la temperatura fue 34.87°C, la fuerza 63 kg y los ciclos por minuto fue de

140 movimientos; y el mínimo en: la temperatura fue 29.38°C, la fuerza 32 kg y los ciclos por

minuto fue de 100 movimientos. Conclusiones: En base a este estudio se concluye que: existe

correlación entre temperatura contra los ciclos por minuto y entre la fuerza contra ciclos por

minuto; asimismo que no existe correlación entre temperatura y fuerza.

Palabras clave: Temperatura, Fuerza, Ciclos por minuto.

ABSTRACT. The need to protect workers against the causes of occupational diseases and accidents

is a no doubt question. Hence the interest to analyze the behavior with variables in temperature in

the area of the wrist, strength and cycles per minute, that to perform horizontal repetitive

movements of the wrist, which are commonly found in workplaces. Objective: The objective was to

correlate the variables of temperature, strength and number of movements per minute when working

with horizontal repetitive movement of the right hand wrist area. Delimitation of the problem: It was

simulated a working day of 8 hours with 2 operators (man and women) exerting horizontal

movements, on the installations of the Faculty of Engineering Ensenada of the Autonomous

University of Baja California. Methodology: It was simulated a working day with two operators

exerting horizontal movements, and for this making the temperature recorder in the area of the

right hand wrist (sensorial thermograph Sköll), the strength of the operator (dynamometer wrist-

twisting Baseline) and cycles per minute, the three mentioned records were made every ten

minutes. Results: The obtained results were: in the operator 1 ,there was a correlation in cycles

per minute against temperature and against strength, besides the maximum in: temperature was

35.93°C, strength was 82 kg and cycles per minute was 138 movements and the minimum in:

temperature was 28.11°C, strength was 36 kg and cycles per minute was 93 movements; in the

operator 2: there was a correlation in cycles per minute, besides the maximum in: temperature



was 34.87°C, strength was 63 kg and cycles per minute was 140 movements and the minimum in:

temperature was 29.38°C, strength was 32 kg and cycles per minute was 100 movements.

Conclusion: On based on this study the conclusion was: correlation exists between temperature

against cycles per minute and strength against cycles per minute; and there is no correlation

between temperature and strength.

Keywords: Temperature, Strength, Cycles per minute.

1. INTRODUCTION

The need to protect workers against the causes of occupational diseases and accidents is a

question no doubt. All sources of work should carry out activities aimed at the prevention of

occupational hazards, with consequent advantages in production and productivity, achieving

greater social welfare, which is reflected in the economy of the company. The ergonomic

approach is to design products and work to adapt them to the people and not vice versa. The logic

that uses the ergonomics is based on the principle that people are more important than the

objects or production processes; and therefore, cases where it arises any conflict of interest

between people and things, should prevail people (Tortosa et al., 1999).

Ergonomic hazards have been an issue to consider, for injuries caused to workers in work areas.

For industry it is always important the health of the workers, because by avoiding the DTA's in it

reduces their costs for disabilities, absenteeism and more importantly for investors.

Musculoskeletal injuries are disorders characterized by an abnormal condition of muscle, tendons,

nerves, vessels, joints, bones or ligaments, which results in impairment of motor or sensory

function caused by exposure to risk factors: repetition, strength, inappropriate postures, contact

stress and vibration (Sinclair, 2001). For example, some of the injuries and illnesses common in

the wrist area causing repetitive or poorly designed work are:

• Tenosynovitis: is an inflammation of the synovial capsule, this is the sheath that covers

tendons. Tenosynovitis can occur in any tendon with a synovial sheath. However, most often



occurs in the hand, wrist or foot. Most cases of tenosynovitis are caused by injury, infection,

twisting, repetitive movement as: operate a computer, working on an assembly line, the cashier of

a bank, sewing, playing musical instruments like violin or guitar

(http://nlmnih.gov/medlineplus/ency/article/001242.htm)

• Ganglia: it is a cyst in a joint or tendon sheath, usually in the back of the hand or wrist.

(http://www.itcilo.it/actrav/osh_es/módulos/ergo/ergoa.htm)

• Epicondylitis: is an inflammation of muscle attachments at the epicondyle of the elbow, the

pain may appear in the muscles of the forearm and wrist. The causes that provoke are: Task force

loading and repeatability, often in stressful jobs such as carpentry, plastering or bricklaying.

(http://www.tiroriojano.com/lesiones/EPICONDILITIS.htm)

• Crimping finger: is an inflammation of the tendons and / or tendon sheaths of the fingers.

By use of air guns or staplers (International Labor Organization, 2004).

• Carpal Tunnel Syndrome: presented by the type of horizontal repetitive movement and the

disease that affects people. It is a Repetitive Strain Injury better documented, currently classified

as compensable occupational disease in many countries. This syndrome affects the median nerve

(one of the principal nerve in the wrist). Extreme cases can lead to permanent disability due to the

absolute inability to flex the wrist to perform tasks as simple as operating a computer or holding an

object in the hand. Affects workers who process meat or poultry, supermarket cashiers who use

electronic scanners, the use of vibrating hand tools.

In the United States with this syndrome each worker loses more than 30 working days, a figure

higher than absenteeism from amputations and fractures. It has been estimated annual cost of

these lesions in more than 100 million dollars (International Labor Organization, 2004).

These injuries and illnesses caused by workplace tools and poorly designed or inappropriate

usually develop slowly over months or years. However, a worker wills usually signs and symptoms

for a long time to indicate that something is wrong. For example, the worker will be uncomfortable

while doing their work or feel pain in muscles or joints once home after work. You can also have

small muscle twitches for some time. It is important to investigate the problems of this kind,

because what may begin with a mere inconvenience in some cases can end in injury or disease

that severely incapacitated workers.



Employees often have no choice and are forced to adapt to poorly designed work conditions that

can seriously injure the hands, wrists, joints, back or other body parts. In particular, injuries can

occur due to:

• The repeated use over time vibrating tools and equipment,

• Tools and tasks that require turning the hand movements of the joints, for example the work

performed by many mechanics;

• The application of strength in a forced position;

• The application of excessive pressure on parts of the hand, back, wrists or joints.

All of them will generate absenteeism and each day of absenteeism for health reasons is a cost. A

day lost disability implies a direct cost and indirect. (Beevis, 2003; Derango, 2002; Hendrick,

2003).

This study aims to correlate the variables of temperature, strength and cycles per minute all this

by repetitive horizontal movements, applied to a man and a woman which are commonly found in

workplaces.

The benefit of this study is that it will have social impact, economic and scientific:

• The social impact, achieving avoid injury to the worker and it will be productive in your work area

and have better social welfare.

• The economic impact, because if the DTA's are avoided in work areas will reduce annual costs

by the company.

• The scientific impact, because it is a sensorial thermography technique actually not used.

1.1 Related Articles Gold et. al., (2004) in the article entitled "Infrared Thermography for Examination of skin

temperature in the dorsal hand office workers", identified differences between skin temperatures

between 3 groups of office workers through dynamic thermography, we have the experiment when

writing computer keyboard for 9 minutes at a time. It highlights the temperature of testing room as

an important factor.



Ming, et. al., (2005) in the article entitled "Sympathetic pathology evidence by hand thermal

anomalies in carpal tunnel syndrome", the aim of this study was to classify the pathology

compassionate in carpal tunnel syndrome and the use of infrared thermography. Exercise was

conducted in which subjects were kept at room temperature between 22 and 25˚C for 15 minutes

at room temperature are highlighted in the testing room as an important factor.

Zontak, et. al., (1998) in the article entitled "Dynamic Thermography: Analysis of hand

temperature During exercise", the aim of this study was to characterize the effect of exercise and

responses in the skin temperatures due to controlled levels of exercise temperature conditions,

making a ergonomics bicycle.

Tchou, et. al., (1991) in the article entitled "Thermographic observations in unilateral carpal tunnel

syndrome: Report of 61 cases", its purpose was to characterize the effect of exercise and

responses in the skin temperatures, as an exercise the balance of hands for 15.

Kyeong-Seop, et. al., (2006) in the article entitled "Infrared Thermography in Human Hand"

estimated temperature conditions that could cause mental stress. Dipping both hands in a

container of water at a temperature of 3˚C.

Ferreira, et. al., (2007) in the article titled "Exercise-Associated Thermographic Changes in Young

and Elderly Subjects", determined thermographic temperature changes associated in elderly and

young people, doing knee bends with a weight of 1 kilogram added to the same for 3 minutes.

2. OBJECTIVE

This study presents the following objectives:

• To correlate the variables of temperature, strength and number of movements per minute when

working with horizontal repetitive movement of the right hand wrist area.

• To show the application of sensorial thermography.

• To develop preliminary test emulating a manufacturing industry repetitive operation.



3. METHODOLOGY

This study was performed at the facilities of the Autonomous University of Baja California from 5

to September 11, 2009. The study involved a man and a woman using the dominant hand (both

being right-handed), which are healthy people with age 24 being the average age of the

economically active population, students in undergraduate and in unskilled industrial manual

material handling.

To achieve the objective of this study, was simulated eight-hour workday to exercise horizontal

repetitive movements as shown in Figure 1.

Figure 1: Horizontal repetitive movement

The record was made to register the temperature in the area of the wrist with a sensorial

thermograph Sköll for each operator placed at the height of the wrist in the right hand figure 2, the

strength of the individual with a dynamometer wrist-twisting Baseline (Figure 3) and cycles per

minute.

Figure 2: Sensorial Thermograph Sköll



Figure 3: Dynamometer wrist-twisting Baseline It is noteworthy that the three records mentioned above were made with a timer (Figure 4) every

ten minutes.

Figure 4: Timer

4. RESULTS

The table 1 and 2 are shown in the data from the experiment with horizontal repetitive movement

of the operator 1 and the operator 2 within 7 days. In the second line of the both tables: 1 means

cycles per minute, 2 means strength and 3 means temperature.



Table 1. Data concentrate of the operator 1 in the 7 days.



Table 2. Data Concentrate of the operator 2 in the 7 days.



4.1 Analysis of correlation. In the figure 1 is shown the correlation between temperature and strength in the 7 days, where r is

0.041. As r is 0.041 and 0.119 which is lower than the critical value we conclude that H0 is not

rejected as there is insufficient evidence to conclude that there is a significant linear correlation.

Figure 1: Correlation between Temperature (°C) and Strength (Kg) of the operator 1 in the 7 days.

In the figure 2 is shown the correlation between cycles per minute and temperature in the 7

days, where r is 0.292. As r is 0.292 and 0.119 which is greater than the critical value we conclude

that there is a significant linear correlation, and H0 is rejected.

Figure 2: Correlation between cycles per minute and temperature (°C) of the operator 1 in the 7 days.



In the figure 3 is shown the correlation between cycles per minute and Power in the 7 days, with r

of 0.266. As r is 0.266 and 0.119 which is greater than the critical value we conclude that there is

a significant linear correlation, and H0 is rejected.

Figure 3: Correlation between cycles per minute and

strength (Kg) of the operator 1 in the 7 days.

The table 3 is shown the results obtained from the variables of the operator 1 in the 7 days.

Table 3: Results of the Operator 1 variables in the 7 days.

The table 4 is shown the maximum and minimum values of the variables of temperature, strength

and cycles per minute generated by day to perform horizontal repetitive movement of the operator

1.



Table 4: Results of the operation range of the operator 1 per day.

In the figure 4 is shown the correlation between temperature and strength in the 7 days, being r -

0.072. As r is -0.072 and 0.119 which is lower than the critical value we conclude that H0 is not

rejected as there is insufficient evidence to conclude that there is a significant linear correlation.

Figure 4: Correlation between Temperature (°C) and Strength (Kg) of the operator 2 in the 7days.

In the figure 5 is shown the correlation between cycles per minute and temperature in the 7 days,

with r -0.172. As r is -0.172 and its absolute value is 0.172 and 0.119 which is greater than the

critical value we conclude that there is a significant linear correlation, and H0 is rejected.



Figure 5: Correlation between cycles per minute and temperature (°C) of the operator 2 in the 7 days.

In the figure 6 is shown the correlation between cycles per minute and Strength in the 7 days,

being r -0.002 As r -0.002. and 0.119 which is lower than the critical value we conclude that H0 is

not rejected as there is insufficient evidence to conclude that there is a significant linear

correlation.

Figure 6: Correlation between cycles per minute and Strength (Kg) of the operator 2 in the 7 days.



The table 5 is shown the results obtained from the operator 2 variables in the 7 days. Table 5: Results of the operator 2 variables in the 7 days.

The table 6 is shown the maximum and minimum values of the variables of temperature, strength and

cycles per minute generated by day to perform horizontal repetitive movement in the operator 2.

Table 6: Results of the operating range of the operator 2 per day.

5. CONCLUSIONS In the present study fulfilled the objective of correlating the variables temperature, strength, and

cycles per minute that are manifested in the wrist area of the dominant hand (in this case the

operators was the right hand) with horizontal repetitive movements during working day within a

week.

On based on this study the results were as follows: the operator 1 ,there was a correlation in

cycles per minute against temperature and against strength, besides the maximum in:

temperature was 35.93°C, strength was 82 kg and cycles per minute was 138 movements and the

minimum in: temperature was 28.11°C, strength was 36 kg and cycles per minute was 93

movements; the operator 2: there was a correlation in cycles per minute, besides the maximum in:

temperature was 34.87°C, strength was 63 kg and cycles per minute was 140 movements and the

minimum in: temperature was 29.38°C, strength was 32 kg and cycles per minute was 100

movements.



The conclusion was: correlation exists between temperature against cycles per minute and

strength against cycles per minute; and there is no correlation between temperature and strength.

6. REFERENCES

Beevis, D., (2003). Ergonomics-Costs and Benefits Revisited. Applied Ergonomics 34: 491-496. Derango, K. and Franzini, L., (2002). Economic Evaluations of Workplace Health Interventions:

Theory and Literature Review. In Handbook of Occupational Health Psychology, Ed Washington D.C. American Psychological Association.

Ferreira, J., Mendonça, L.C., Nunez, L.A., Andrade, A.C., Rebelatto J.R., and Salvini, T. (2007). Exercise-Associated Thermographic Changes in Young and Elderly Subjects, Federal University of Saint Carlos. Physics’ Institute of Saint Carlos, Sao Paulo University, Brazil.

Gold E. J., Cherniack M., Buchholz B., (2004). Infrared Thermography for examination of skin temperature in the dorsal hand office workers, Eur J. Apply Physiol 93: 245-251.

Hendrick, H.W., (2003). Determining the Cost-Benefits of Ergonomics Projects and Factors that lead to their Success. Applied Ergonomics 34: 419-427.

International Training Center of the International Labor Organization. ITCILO: Home page. http://www.itcilo.it/actrav/osh_es/módulos/ergo/ergoa.htm

Kyeong-Seop, K., Shin, S.W., Yoon, T.H., Kim, E.J., Lee, J.W. and Kim, I.Y. (2006). Infrared Thermography in Human Hand”, School of Biomedical Engineering, Chungju, Korea.

Ming, Z., Zaproudina, N., Siivola, J., Nousiainen, U., Pietikainen S., (2005). Sympathetic pathology evidenced by hand thermal anomalies in carpal tunnel syndrome, ISP Pathophysiology: 137-141.

International Labor Organization (2004). Labor Productivity in Latin America, is the same as 20 years ago, Magazine of occupational panorama of the OIT.

Sinclair, D.T. and Graves, R.J. (2001). Feasibility of Developing a Simple Prototype Decision Aid for the Initial Medical Assessment of Work Related Upper Limb Disorders. University of Aberdeen. Department of Environmental & Occupational Medicine. Hse Books.

Shooting Sport Club La Rioja, Shooting Sport Club La Rioja Home page: http://www.tiroriojano.com/lesiones/EPICONDILITIS.htm

Tchou, S.F., Costich, J.C. Burguess, R., Lexington, K.Y. and Wexler C. (1992). Thermographic observations in unilateral Carpal Tunnel Syndrome: Report of 61 cases, The Journal of the hand surgery 17A: 631-637.

Tortosa, L. and Garcia, C., Page, A. and Ferreras, A. (1999). Ergonomics and disability. Institute of Biomechanics of Valencia (IBV), Valencia. ISBN 84-923974-8-9.

U.S. National Library of Medicine and National Institutes of Health. Medical Encyclopedia: Home page. http://nlm.nih.gov/medlineplus/ency/article/001242.htm

Zontak, A., Sideman, S, Verbitsky, O. and Beyar, R., (1998). Dynamic Thermography: Analysis of hand temperature, Annals of Biomedical Engineering, Vol. 26, 988-993.



Temperature analysis on wrist surface due repetitive movement tasks using Sensorial Thermography to find out a possible pathology for a CTD

Ordorica Villalvazo Javier 1,2, Camargo Wilson Claudia1,2, De la Vega Bustillos Enrique3,

Olguín Tiznado Jesús E.1, 2, López Bonilla Oscar R.2, Limón Romero Jorge1, 2.

1 Department of Industrial Engineering - Engineering Faculty Ensenada. Autonomous University of Baja California. Km. 103 Highway Tijuana-Ensenada S/N

Ensenada, Baja California. 22760 [email protected], [email protected]

2 Division of Posgrade and Research MyDCI- Engineering Faculty Ensenada.

Autonomous University of Baja California. Km. 103 Highway Tijuana-Ensenada S/N

Ensenada, Baja California. 22760 [email protected], [email protected], [email protected]

3 Division of Postgraduate Studies and Research.

Technological Institute of Hermosillo. Technological Avenue S/N Hermosillo, Sonora. 83170 [email protected]

Resumen: A través de la historia se puede observar como la temperatura ha sido un indicador

importante para determinar cambios importantes en los ecosistemas del planeta, en la resistencia

de materiales para el diseño de nuevos productos, y también en el campo de la medicina

analizando por ejemplo, fiebres ocasionadas por infecciones provocadas por nuevas

enfermedades. A través de este estudio de las variaciones de temperatura corporales provocadas

en los nervios del área de la muñeca generando la reducción en la habilidad muscular para

realizar el trabajo debido a movimientos repetitivos, lo cual nos puede llevar a entender la

patología de un Desorden de Trauma Acumulado (DTA), tomando en cuenta la termografía

sensorial, ya que no es invasiva para el ser humano, que facilita la recolección y manipulación de

los datos. Objetivos: Analizar cambios en los patrones de temperatura generados en el área de la

muñeca. Mostrar la factibilidad de la aplicación de la termografía sensorial. Recabar información

acerca de las variables no laborales (edad, género, peso, entre otras) y laborales (repetitividad,

temperatura del área de trabajo). Desarrollar las pruebas preliminares emulando la operación

ejecutada en la industria y que involucra los movimientos repetitivos. Identificar los puntos de

estrés máximo alcanzados durante un periodo de operación describiendo síntomas detectados.



Delimitación del problema: Este estudio se realizó con sólo un estudiante de la Facultad de

Ingeniería Ensenada de la UABC. Metodología: Se seleccionó a un estudiante en condiciones

físicas normales, quien realizó pruebas en un laboratorio aplicando el protocolo para el

experimento haciendo uso de la termografía sensorial. Resultados: Las temperaturas máximas

alcanzadas en ambas muñecas fueron en periodos de operación en tiempos muy similares. Se

detectaron molestias en el hombro derecho en el rango donde se identifican las temperaturas

más altas durante el proceso de la operación para ambas muñecas. A través del ajuste de una

ecuación de tercer orden fue posible explicar el comportamiento de las temperaturas.

Conclusiones: Por medio de la termografía sensorial es posible analizar patrones de temperatura,

ligarlos a una estadística creando la posible patología de un DTA y que pudieran servir en futuras

investigaciones.

Palabras clave: Termografía sensorial, DTA, temperatura.

Abstract: Through history we have observed how temperature has been an important factor to

take in account in order to detect many several climatic changes in planet. This factor has been

deeply studied in weather changes, material resistance for the designing of new products, and

also, in the medicine field obtaining remarkable results studying fiber causes in multiple diseases,

most of them related to infections. This research aimed at evaluating body temperature variations

on wrist surface that can cause muscle disability and weakness due repetitive movement tasks.

The work contributes to discover a possible Cumulative Trauma Disorder (CTD) pathology using

sensorial Thermography as an innovative and dynamic tool, since this is not a non-invasive

technique it means that can not cause any damage on humans. It is a powerful tool also, because

allow investigators to manipulate data and import or export them to statistics programs.

Objectives: Analyze temperature pattern changes and show up the feasibility of the sensorial

thermography. Collect information about different kind of variables that may affect the study, like

age, gender, weight, height, and others like repetitiveness and work area temperature. Perform

preliminary test emulating an operation highly repetitive in the textile industry. Identify maximum

stress points while preliminary test is taking place, and at the same moment detect key symptoms.

Methodology: An Industrial engineering student in good shape was selected to perform the

repetitive task in a lab by following the experiment protocol and using sensorial thermography.



Results: Maximum temperatures in both wrists were detected in similar periods of time. The

student showed pain symptoms in right shoulder while doing the task. It was detected while the

maximum temperature range was reached in both wrists. By adjusting a third order equation it

was possible to explain the temperature behavior. Conclusions: Through sensorial thermography

is possible to analyze temperature pattern and link them to statistics creating a possible CTD

pathology that could help in future researches.

Keywords: Sensorial thermography, CTD, temperature.

1. INTRODUCTION

The highly repetitive activities are a disease that in nowadays affect thousands of people

developing several cumulative trauma disorders. In many times this kind of disorders are confused

with other kind of diseases. The cumulative trauma disorders cause damages on body tissues due

to excess motion periods. It can be developed through pass of the time. Furthermore, today, the

DTA’S are well known as an industrial epidemic causing a periodic disability. The experimentation

was based on temperature analysis generated on wrist area of one subject, which is the area

where the carpal tunnel syndrome begins. A repetitive movement simulation consisted in an

operation emulated from a local textile industry. The study was taken using sensorial

thermography.

The thermography is a non invasive technique without biologic hazard. It detects, measures, and

converts invisible, surface body heat into visible display which is the photographed or videotaped

as a permanent record. This type of thermography it is the one we call infrared thermography

(Feldman al., 1991). The digital sensorial thermography it is different from the infrared one,

because it is widely used to look for temperature patterns on skin surface through sensor contact

(Zontak et al., 1998).



This technology was born while the submarine thermographs a long time ago were developed to

measure underwater temperatures. It has many applications such as oceanography, marine

ecology, industry, and many others (Lopez, 1992).

This study arose from three important questions, what is the subject temperature behavior during

the motion? What is the relationship between pain symptoms and temperature data? What are the

max stress points? A close examination of the literature shoes that no study has been devoted to

these problems emulating a motion executed in the textile industry in order to analyze cutaneous

temperatures.

However a swimming study was carried out with a professional swimmer in a pool where the

swimmer practiced several swimming styles, so researchers could analyze the temperatures after

each swimming style (Zaidi et al., 2007).

The Study was carried out in a closed room where the temperature was a relevant parameter. We

use a home heater to try to control the temperature, because according with the literature, the

most useful temperature parameter in experimentations of this kind is between 20 and 25 degrees

(E.Y.K, N.G. et al., 2005).

It is advisable to specify that the present work is not a statistical study. The results obtained in this

study cannot be considered to have a universal character since only one subject was taken into

account for our experimentation. However we are doing many test with more subjects at the

campus to make temperature behavior inferences. The objectives in this preliminary

experimentation were to show the applications of the sensorial thermography on one hand, and on

the other hand, to show the maximum temperature stress points.

2. OBJETIVES

This Study presents the following objectives:

• To analyze temperature pattern changes generated on wrist area.



• To show the application of sensorial thermography.

• To collect information about subject gender, age, mass and others.

• To collect information about repetitive cycles and temperature working area.

• To develop preliminary test emulating a textile industry repetitive operation.

• To identify maximum stress points during the operation period and to describe symptoms

detected.

3. METHODOLOGHY

3.1 The subject

The subject taking in part in this study is a subject in good shape. The principal anthropometric

characteristics of the subject are summarized in table 1.

Table 1. Anthropometric data for the subject

Age Height

(m) Mass (Kg)

Subject 29 1.63 60

3.2 Equipment and data analysis

All the cutaneous temperatures were taken using a sensorial thermograph Sköll with a

temperature range of 0˚C – 40˚C, a precision of ±.3˚C, and a resolution of 1 degree, a

microporous tape (Lopez, 1992), a laptop (COMPAQ Intel Pentium Dual Core), a home heater.

Programming the thermographs was possible using a program called Akela. Also a statistical

program was used for data analysis (Minitab 15) and Microsoft Excel 2007.

3.3 Protocol

Subjects were asked to refrain from intense exercise, caffeine, smoking, alcohol and smoking for

20 minutes prior to the experiment (Gold et al., 2004) and (Gold et al., 2009) because smoking



could produce a massive reduction of body temperature and alcohol a raise of body temperature.

Previous studies have demonstrated that the corporal temperature stabilization takes about 20

minutes due to a reduction on body metabolism (E.Y.K NG y Sim en E.Y.NG et al., 2008).

Having the opportunity to use a home heater we warmed up the room temperature for the

experiment between 20-25 degrees (E.Y.K NG et al., 2005), Once we warmed up the room, the

participant was seated in an ergonomic chair with arm rest and then stick the sensorial

thermographs in both wrist, close to the median nerve region. After that, the subject was asked to

rest both arms in a flatbed at the ribs height (Kroemer et al., 2001) for about twenty minutes. The

next step in the experiment protocol was to simulate a highly repetitive operation executed in the

textile industry for about 3.5 hours, this period of time representing the longest period of the

workday. The operation involved several movements like reach, take, place and many others.

Several pain symptoms were identified during the experiment. Finally, the sensor thermographs

were removed from both wrist and then analyze the results.

4. RESULTS

The results of all pain symptoms detected during the experiment developed are shown in table 2.

These anomalies were given off by the subject while he was doing the repetitive task. It was so

important to write down the hour, minute and second, so we could link this info to the

temperatures.

Table 2. Anomalies detected in the operator

Right

shoulder pain

Left shoulder pain

Lower back pain

Upper back pain

Right wrist pain

Right palm pain

Preliminary 1

x

Preliminary 2

x x x x x

Preliminary 3

x x

Preliminary 4

x x x x



4.1 Preliminary test 1 The corresponding temperature behavior is shown in Figure 1 and 2. If we compare both figures

we can see that both temperature behaviors in both wrists are very but very similar. Three similar

characteristics were identified as a result:

• The temperatures in both writs (maximum stress points) were 33.44˚C and 32.921˚C, and were

reached at similar periods of time, 11:41:14 and 11:49:28 (h:m:s).

• The anomalies in right shoulder started to being shown by the person at the range where were

the highest temperature levels, while doing the operation using both wrists.

• The most aggressive projection of the temperature was approximately at 11:30 and 12:00 in

both wrists.

In both cases the subject beated the pain symptoms on right shoulder, this happened when the

most aggressive projection began to appear, approximately at 11:40. Then at the same time the

temperature projection became less aggressive and began a tendency of decrease.

On the other hand, by adjusting a third order equation it was possible to explain the temperatures

of the person with a coefficient of determination of 91.1% for the left hand wrist and 87.7% for the

right hand wrist.

Figure 1. Adjustment of the curve of left hand wrist



Figure 2. Adjustment of the curve of right hand wrist 4.2 Preliminary test 2 The corresponding temperature behavior is shown in Figure 3 and 4. If we compare both figures

we can see that both temperature behaviors in both wrists are very similar has shown in the

previous preliminary test. The maximum time of stress of the hands was to similar one from each

other, and based on this we could say the following important points:

The maximum stress points were reached in similar times in both wrists. On left hand wrist at

12:48:24 and the temperature was 34.276˚C and on right hand wrist was 12:48:39 and the

temperature was 34.154˚C. Factors like temperature and time were similar.

Many anomalies were detected on right wrist around 12:33:30 and after one hour on right

palm, and at the same time on lower back.

Anomalies on right shoulder were detected when the maximum temperature stress point was

reached.

On the other hand it was possible to adjust a polinomial third order equation that represents the

subject temperature behavior and as a result a coefficient of determination of 80.5% for the left

hand wrist and 86.8% for right hand wrist.





we can see that both temperature behaviors in both wrists are very similar has shown in the

previous preliminary test and. The maximum time of stress of the hands was similar one from

each other, and based on this we could say the following important points:



The maximum stress points were reached in similar times in both wrists. On left hand wrist

at 14:11:40 and the temperature was 33.481˚C and on right hand wrist was 14:13:22 and

the temperature was 33.313 ˚C. Factors like temperature and time were similar.

A lower back pain was identified around 12:55:35 and close to the end of the

experimentation a pain on right hand wrist around 14:54:10.

Anomalies on right shoulder were detected when the maximum temperature stress point

was reached.

On the other hand it was possible to adjust a polinomial third order equation that represents the

subject temperature behavior and as a result a coefficient of determination of 90.8% for the left

hand wrist and 94.5% for right hand wrist.





we can see that both temperature behaviors in both wrists are similar has shown in the previous

preliminary test and. The maximum time of stress of the hands was to similar one from each other,

and based on this we could say the following important points: The maximum stress points were reached in similar times in both wrists. On left hand wrist

at 12:52:14 and the temperature was 33.686˚C and on right hand wrist was 13:03:53 and

the temperature was 33.114˚C. Factors like temperature and time were similar.

A lower back pain was identified around 12:55:35 and close to the end of the

experimentation a pain on right hand wrist around 14:54:10.

Anomalies on right shoulder were detected during the period when the temperature began

to decrease around 13:42:52. Also a pain on right palm was identified around 14:13:43.

At the end of the test a pain on left shoulder was identified around 3:52:40 and also the

pain on right shoulder increased in a several way, this occurred around 3:56:36.

On the other hand it was possible to adjust a polinomial third order equation that represents

the subject temperature behavior and as a result a coefficient of determination of 97.3% for

the left hand wrist and 95.6% for right hand wrist.




Figure 8. Adjustment of the curve of right hand wrist

4.5 Averages

Taking in account the maximum temperatures reached in the experiment stress points of all the

preliminary test of both hand wrists, we obtained averages for each hand wrist, and the equation 1

shows how to calculate the averages:



n

yy

n

ii∑

== 1 (1)

We found out, and based on having similar temperature patterns and stress point periods that

averages were similar too. The average temperature for left hand wrist was 72.33=y ˚C and

38.33=y ˚C for the right hand wrist.

5. CONCLUSIONS

A preliminary experimental test was undertaken on one hand, for studying the feasibility of using

sensorial thermography on the analysis of repetitive tasks, and on the other hand to identify the

maximum stress point, behavior and temperature patterns as a result of the activity. In particular,

this study shows that the use of the sensorial thermography is appropriate in order to detect

temperature patterns. It is remarkable to mention that in all the test the temperature patterns were

very similar in both hand wrists, independently of the dominant hand of the subject. The

temperature patters were similar for all the tests, but changing its behavior during the days. The

same conditions were taking in account for the entire tests, including the room temperature as the

main element.

On the other hand it was possible to adjust a polinomial third order equation for each test that

represents the subject temperature data behavior and as a result a coefficient of determination to

represent the level of the curve adjustment to data.

6. RECOMENDATIONS

One should recall to this conclusions cannot be considered as universal as far as only one

subject, a subject in good shape, took part in this study. Nevertheless, the conclusions make us



think of considering a statistical study taking in part more subjects (men and women), to verify if

the temperature patters of several subjects are linked in same way.

7. REFERENCES E.Y.K, N.G. and E.C., K.E.E., (2008). Advanced integrated technique in breast cancer

Thermography, Journal of Medical Engineering & Technology, Vol. 32, 103-114. Feldman, F., (1991). Thermography of the hand and wrist: Practical applications, Hand Clinics,

Vol. 7, No.1. Gold, J., Cherniack, M., Hanlon, A., Dennerlein, T., Dropkin, J., (2009). Skin temperature in

dorsal hand of office workers and severity of upper extremity musculoskeletal disorders, Int. Arch. Occup. Envior. Health, 82: 1281-1292.

Gold, J., Cherniack, M., Buchholz, B., (2004). Infrared Thermography for examination of skin temperature in the dorsal hand office workers, Eur J. Apply Physiol 93: 245-251.

Kroemer, E., Kroemer, H., Kroemer. K., (2001). “Ergonomics: How to design for ease and efficiency”, second edition, Prentice Hall, ISBN 0-13-725478-1, 97-113.

Lopez, R., (1992). Oceanologic Research Institute, Autonomous University of Baja California. Submarine digital thermograph, Develop and instrumentation, Vol. 3 No.2, 1992

Puig A.A., (1993). Smoking influence in the variations of biochemical, physiological and performance parameters, Barcelona, Spain.

Zaidi H., TaÏar R., Fohanno S., Polidori G., (2007). The influence of swimming type on the skin-temperature maps of a competitive swimmer from infrared Thermography, Acta of Bioengineering and Biomechanics, Vol. 9, No.1.

Zontak Alla, Sideman Samuel, Verbitsky Oleg, Beyar Rafael, (1998). Dynamic Thermography: Analysis of hand temperature, Annals of Biomedical Engineering, Vol. 26, 988-993.



VIBRATION STUDY TO IMPROVE STRIPPING OPERATION IN A LITOGRAPHICS COMPANY

Mario Ramírez Barrera ¹, Jorge Valenzuela Corral ¹

Athenea Núñez Sifuentes ˚ ¹ Industrial and Manufacturing Engineering Department ˚ Student from Institute of Engineering and Technology

Universidad Autónoma de Ciudad Juárez

[email protected] , [email protected] [email protected]

RESUMEN: En una empresa dedicada a la impresión y elaboración de cajas y precisamente en

la operación de striping. o desbarbe que es donde se cortan los excesos o sobrantes de las cajas

después del proceso de sauje (marcado o preformando por medio de prensas), nos encontramos

que en esta operación los trabajadores se encuentran expuestos a los mas importantes factores

de riesgo ocupacional como son frecuencia, esfuerzo energético y mala postura, pero sobre todo

a una sobreexposición de vibración producida por un roto martillo neumático utilizado para quitar

el cartón sobrante o la rebaba de las cajas durante la operación de striping, y es por esto que en

esta investigación se analizo el uso de dicha herramienta y se vio que al utilizar un aislante

adecuado en el mango del roto martillo neumático y los guantes ergonómicos anitimpacto y

antivibración en vez de los de algodón que actualmente proporciona la empresa se reduce al

máximo el estrés de trabajo producido por la vibración, así como también al utilizar el equipo de

protección personal consistente en tapones auditivos, mascarillas y zapatos de seguridad se

mejora considerablemente el entorno del operador y así se podrá reducir considerablemente el

riesgo de adquirir una enfermedad profesional generada por el tipo de trabajo requerido por el

proceso de fabricación del producto.

Palabras Clave: Vibracion, Equipo de protecion personal.

ABSTRACT:The comparative study was made in a company dedicated to fabricate and print

carton boxes. After the carton press forming process there is an operation that removes carton

excess and leftovers which was found that workers are exposed to an occupational risk



conditions like frequency, body stress and bad postures besides of an overexposure vibrations

condition originated from a pneumatic roto-hammer utilized to remove carton leftovers during the

stripping operation , and that is why this investigation was focused in the use of this pneumatic

tool. After a close analisys of the situation it was found that by adding the proper insulation to the

tool handle and by using anti-impact / anti-vibration ergonomic gloves instead of the normal cotton

gloves provided by the company, the stress condition due to the tool vibrations was drastically

reduced, in addition to this the personal protection equipment was improved by utilizing ear plugs,

mask and safety shoes, and as a result of these actions the work environment conditions were

improved thus reducing the probability of getting a body trauma due to the fabrication process

needs.

Key words: Vibrations, Personnel Protection Equipment.

1. INTRODUCTION After the carton Fabrication and Printing process there is a stripping operation which consists of

two steps: carton preforming by utilizing a pneumatic roto-hammer and manual removal of

leftovers from cartons located on pallets, figures 1.1 and 1.2 below show the fabrication process

sequence.

Figure 1.1 Preforming of boxes using Figure 1.2 Manual carton leftovers the pneumatic roto- hammer removal.



In the operation mentioned above it was found that the workers were exposed to significant

occupational risk conditions such as frequency, body stress and anti-ergonomic postures and also

an overexposure to vibrations for extended periods of time affecting arms and hands due to the

use of this roto-hammer tool, the workers were just using normal cotton gloves, also a survey was

made finding that workers suffer from chronic back ache, weakness sensation of hand grasping

ability known as Accumulative Trauma Disorder (ATD) in tendons and nerves which was

developed due to this working condition for an extended period of time.

2. INVESTIGATION METHODOLOGY

Investigating carefully to get the proper analyzing data in order to improve this workstation, a

Vibrations meter was used ( Bruel & kkjaer”s model vibrotest 60 shown in figure 2.1 ). Vibrations

readings were taken using just regular cotton gloves as shown in figure 2.2 to make the

comparisson against utilizing anti-impact / anti-vibrations ergonomic gloves and also an insulator

material was installed on the roto-hammer handle to help improving this situation. Finally the

readings were taken on both conditions and they are shown on the following tables .

Figure 2.1 Vibrations Analyzer Figure 2.2 Vibrations readings taken at Utilized in the study Stripping work station.



The data was carefully analyzed and charts were obtained to compare before and after conditions

(1 µm = .001 mm = 1 x 10 ¯³ mm measuring units were used ) , without cotton gloves, with cotton

gloves, with anti-impact / anti-vibtations gloves and last the insulation on the tool handle.was

added. Chart figure 2.3 shows this data.

Figure 2.3 This chart shows the average of vibration readings using this analyzer . without gloves

(blue), with cotton gloves (purple), With ergonomic gloves (green), with both ergonomic gloves

and handle insulation (red).



3. RESULTS Based on the detailed ergonomic analysis made and considering the vibrations condition that the

regular worker is exposed to during extended periods of time , It is strongly recommended to re-

design and relocate this work station to make it safer and easier to handle the material used , and

also it is suggested to break-down this operation in two steps physically separated from each

other (pre forming and manual leftovers removal as shown in figure 3.1) in order to rotate

operators every two hours in each step of the operation , place an anti-fatigue floor mat and at the

same time insulating the handle of the roto-hammer pneumatic tool ( figure 3.2) and also utilizing

anti-vibrations / anti-impact ergonomic cotton gloves / spandex and with akton material on the

hand palm area to reduce the vibrations impact (figure 3.3), in addition to that , safety shoes with

steel must be used at all times , as well ear plugs, and mouth mask to avoid contact with the

carton dusts.

. BEFORE AFTER

ANTES

DESPUES

Figure 3.1 Layout of the stripping operation before and after the improvement showing the operation separated in two steps and physically separated also.



Figure 3.2 Insulation of tool handle Figure 3.3 Anti-vibration/impact gloves

4. CONCLUSIONS

The level of vibration due to the use of certain tools can be reduced to avoid a higher

damage to the human body by taking several actions like rotation of workers (Administrative

controls) more often , proper maintenance of tools to prevent malfunctioning, Installation of

anti fatigue floor mats to isolate vibrations from human body,Anti-vibration devices like

plastics or foams adapted to the tools or machines (Engineering controls). And also the use

of personnel protection equipment like anti-vibration / anti-impact gloves. The lesson learned

from this study , most important from all this, is to change or improve Company’s safety

practices culture to protect workers by meeting Official Mexican Safety Norms (nom 017 and

nom 024) at the workplace, and to train , and implement awareness programs aim to

employees through visual and verbal communications medias to make them aware of the

possible body damage due to long exposure of vibration conditions resulting in possible

traumas. (Human administrative controls).*

* Mario Ramirez Barrera (UACJ 2010)



5. BIBLIOGRAPHY

• Asfahl C ,R. Industrial Safety and Health managment ( 1995) 3ª Edition editorial Prentice Hall.

• Bailey R. Human Performance Engineering. ( 1989) Prentice Hall.

• International Organization for Standarization (2004) ISO 2631.5.2004 Mechanical vibration

- Evaluation of human exposure to whole body vibration. ISO Switzerland

• Normas Oficiales Mexicanas ( nom 017 y nom 024)



A Descriptive Study about the Integration of Ergonomic Attributes on the Selection of Advanced Manufacturing Technology -AMT-

Aidé Maldonado Macías1, 2, Arturo Reallyvázquez1, Guadalupe Ramírez1, Jorge Garcia-

Alcaraz1, Salvador Noriega1

1 Department of Industrial and Manufacturing Engineering

Ciudad Juárez Autonomous University Ave. del Charro 450 Norte, C.P. 32310

Cd. Juárez, Chihuahua, México [email protected]

2 Division of Graduate Studies and Research

Ciudad Juárez Institute of Technology Ave. Tecnológico No. 4090

Cd. Juárez, Chihuahua, México

Resumen: Este artículo presenta un estudio descriptivo sobre la integración de la Ergonomía de

compatibilidad de atributos (ECA) en la selección de la Tecnologia de Manufactura Avanzada

(TMA) entre 30 personas que toman decisiones (TD) de las empresas del sector metal-mecánico

situado en la zona fronteriza de Ciudad Juárez, México. La intención es aumentar el conocimiento

sobre la consideración e importancia de los atributos ergonómicos en la adquisición de TMA.

Además, fueron investigadas algunas de las características del personal que participa en su

funcionamiento, la gestión y la toma de decisiones. Adicionalmente, se identificaron los

procedimientos comunes de evaluación y selección de TMA; se da una clasificación de los

equipos utilizados en estas empresas de acuerdo con el propósito de manufactura.

La metodología expone la ECA en un modelo de atributos múltiples y describe la ECA aplicada

para recabar información sobre las características de la selección de la TMA, selección de

proocesos utilizados en estas empresas. Los resultados muestran que la mayoría de las

empresas realizan algún tipo de diagnóstico para la selección de AMT, pero frecuentemente se

omiten o descuidan los atributos ergonómicos. Sin embargo, los TM reconocen que al tomar en

consideracion los atributos ergonomicos en la selección de TMA puede proporcionar una ventaja

estratégica al facilitar y promover condiciones operativas más seguras en estos lugares de trabajo

y lograr una mejor aplicación de esta tecnología también. Asimismo, los resultados indican que es

casi tan frecuente encontrar en estas empresas la tecnología CNC como la tecnología tradicional



y una tendencia cada vez mayor para incrementar las inversiones en tecnología de robots y

prototipado rápido. Además, el genero masculino es predominante en el personal operativo y

administrativo relacionado con TMA y el personal operativo promedia una antigüedad en un rango

de 4-7 años.

Palabras clave: Ergonomia de Compativilidad de Atributos, Tecnología de Manufactura

Avanzada, Toma de Decisiones, Encuesta de compatibilidad ergonómico para TMA

Abstract: This paper presents a descriptive study about the integration of Ergonomic

Compatibility Attributes (ECA) on the selection of Advanced Manufacturing Technology (AMT)

among 30 Decision Makers (DM) from enterprises of the metal-mechanical sector located in the

borderland of Juarez City, Mexico. It is meant to increase knowledge about the consideration and

importance of ergonomic attributes on the acquisition of Advanced Manufacturing Technology

(AMT). Also, some characteristics of the personnel involved in its operation, management and the

decision making processes were investigated. Additionally, common procedures for evaluation

and selection of AMT were identified; a classification of the equipment used in these companies is

provided according to the manufacturing purpose.

The methodology exposes the ECA in a multi-attribute model and describes the Ergonomic

Compatibility Survey (ECS) applied for gather information about the characteristics of the AMT

selection processes used in these companies. The results show that most of the companies do

perform some kind of diagnosis for AMT selection, but ergonomic attributes are often omitted or

neglected among them. However, DM recognize that ergonomic attributes consideration in AMT

selection may provide a strategic advantage in the way it would facilitate and promote safer

operative conditions in these workplaces, and a more successful implementation of this

technology as well. Also, results explain that CNC technology is almost as frequent to find in these

companies as traditional technology and a growing trend to increment the investments in rapid

prototyping technology and robots can be observed. Additionally, male gender is predominant in

the operative and management personnel related with AMT and operative personnel average

seniority is in a range of 4-7years.



Keywords: Ergonomic Compatibility Attributes, Advanced Manufacturing Technology, Decision

Making Processes, Ergonomic Compatibility Survey for AMT.

1. INTRODUCTION This section presents the problem description, the objectives of this investigation and finally the

justification and the scope.

1.1 Problem Description According to the Metal-Mechanic Industry Directory 2008 (Directorio de la Industria Metal-

Mecánica, DIMM, by its initials in Spanish) in Juarez City, there are approximately 200 companies

in the field of Metal-Mechanic Industry, which represents an important source of jobs for the city.

Thus, it is believed that there is substantial amount of workers engaged in the use of AMT.

However, studies about the characteristics of the personnel and employees related with the

operation and management of AMT and the integration of safety and ergonomic attributes in the

decision making processes are scarce locally.

It is well known that managers and DM face the problem of selection of many AMT

alternatives; and there are multiple attributes involved in making a good decision, so it is difficult to

consider all in their totality. In this way, this research pretends to explore the integration of ECA on

the selection of AMT among 30 DM in local industries and to promote the consciousness about

the benefits of ergonomics’ implementation.

1.1.1 Objectives

The objectives that arise in this work are divided into three specific and one general goal, which

are explained below:

1.1.1.1 General Objective

Increase knowledge about the consideration of ergonomic attributes on the acquisition of

Advanced Manufacturing Technology (AMT) by means of a descriptive study and the application

of the ECS to 30 DM in local companies.



1.1.1.2 Specific Objectives

Describe some important characteristics of the personnel involved in its operation, management

and in the decision making processes for AMT acquisition.

Identify common procedures for evaluation and selection of AMT.

Provide a classification of the equipment used in these companies according to the manufacturing

purpose.

Increase knowledge about the reasons they may or may not include ergonomic and safety

attributes on their decision making processes.

1.1.2 Justification and Scope This research will provide information to managers and investors of the Metal Mechanic Industry

about the integration of ergonomic attributes on the selection of AMT, which may have been

previously obviated. According to Helander (2006), companies that take into account the

ergonomic attributes on the selection process of AMT will result in safety, productivity and

satisfaction of their workers.

This work was made in the Metal Mechanic Industry in Ciudad Juarez, Mexico, where an ECS

was applied to DM to know some characteristics of their planning and selection processes of AMT

and the personnel involved in such processes.

2. LITERATURE REVIEW Ergonomic and safety aspects are significant for the design and operation of complex

manufacturing systems like the ones related with AMT. These are being under estimated for the

control of injuries and safety problems in the Manufacturing Industry (Karwowski, 1990, 2005).

According to the Bureau of Labor Statistics of the United States, the Mexican Social Security

Institute (IMSS), the European Agency for Safety and Health at Work, and the Report of Labor

and Social Trends in Asia 2006 nowadays the Manufacturing Industry occupies one of the top five

industries with the highest number of injuries, illnesses, days away from work, along with other

important statistics worldwide. Additionally, in Mexico the operation of tools and machines is one

of the top five occupations that report the highest numbers of these events also. However, there

are difficulties to relate these events with the operation of AMT, due to insufficient information and



lack of attention to this topic (Maldonado, 2009). Important authors recognize that even when AMT

was introduced among others reasons to reduce safety risks and hazards for humans, new and

more critical ergonomic and safety risks have been detected since its introduction in

manufacturing processes (Nicolaisen, 1995; Karwowski et. al., 1988; Karwowski and Salvendy,

2006; Sugimoto et. al., 1985).

In this way, managers and DM may have underestimated Human Factors and Ergonomics

attributes in their decision in the way priority is given to other factors. Also they are unaware of

these attributes and their benefits. Such ignorance has serious consequences for companies and

their workers, since the operators work under physical and mental stress, eventually develop

musculoskeletal trauma disorders and injuries for life, which represents large losses for jobs and

businesses (Prado, 2001).

3. METHODOLOGY

The methodology presents the description of ECA and the ECS.

3.1 Ergonomic Compatibility Attributes Ergonomic Evaluation of AMT is not an easy topic since ergonomic requirements (attributes) are

not clearly determined in the literature and disperse, also it implies quantitative and qualitative

aspects and its complexity and vagueness make an even harder problem to resolve. For

Karwowski (2005), advanced technologies with which human interaction constitute complex

systems that require a high level of integration, he considers that Ergonomic Compatibility

Attributes of AMT have to focus in the design integration of the interactions between hardware

(computer-based technology), organization (organizational structure), information system, and

people (human skills and training). This was the foundation of the literature search, but also

Corlett and Clark (1996) ergonomic guide for machine design was used. In this way, ergonomic

compatibility evaluation main attributes (ECMA) for AMT, were divided into five parts: human skills

and training compatibility (A11), physical work space compatibility (A12), usability (A13),

equipment emissions (A14) and organizational requirements (A15). The main attribute A11

includes two sub-attributes: skill level compatibility (A111) and training compatibility (A121). The

main attribute A12 includes five sub-attributes: access to machine and clearances (A121),



horizontal and vertical reaches (A122), adjustability of design (A123), postural comfort of design

(A124), physical work and endurance of design (A125). The main attribute A13 includes seven

sub-attributes: controls design compatibility (A131), controls’ physical distribution (A132), visual

work space design (A133), information load (A134), error tolerance (A135), man machine

functional allocation (A136), design for maintainability (A137). The main attribute (A14) includes

four sub-attributes: temperature (A141), vibration (A142), noise (A143), residual materials (A144).

The main attribute (A15) includes two sub-attributes: rate of work machine compatibility (A151)

and job content machine compatibility (A152).

3.2 Ergonomic Compatibility Survey

An Ergonomic Compatibility Survey (ECS) was designed for collect the information of the

evaluation of AMT alternatives. The ECS has two versions; one of these versions was designed to

be answered by experts and the other one to be answered by DM. For this work it will be analyzed

the second version (DM). DM’ subjective opinions were needed. The ECS consists on 72

questions but for the effects of this work only the first 22 questions were analyzed covering the

sufficient information to make a descriptive study.

3.2.1 Companies’ General Data

The general data of the companies is requested in the first section of the ECS. Information

includes average occupation and the respective gender. Also the workers’ average age for each

gender is requested and workers’ average seniority to each gender. Finally, the kind of AMT used

in the company is inquired.

3.2.2 Characteristics of the Planning and Selection Process of Advanced Manufacturing

Technology (AMT)

This part includes 17 questions. This section aims to know some characteristics of the planning

process for the acquisition of ATM in the company and who participate in the decision making.

The first 3 questions refer to who makes the final purchasing decision of AMT. The next 3

questions refer to how the AMT is identified and how the selection process is carried out. Finally,

through the last 13 questions the integration of ergonomic and safety attributes on the selection

process of AMT can be observed.



4. RESULTS

This section presents the results obtained of the ECS described above.

4.1 Results of Companies’ General Data This section shows the results of general data company.

4.1.1 Gender and average occupation

Companies of the survey occupy mainly male workers in all positions. According to the survey,

male gender is preferable due to the nature of the work and the applied force that is required in

some activities. The majority of female personnel found in these companies usually have

administrative positions. Figure 1 shows these results. Additionally, average occupation is of 46

workers among the participating companies.

Figure 1. Gender of employees in the Metal Mechanical Sector

4.1.2 Average age of employees

Figure 2 shows that male workers employed have on average 29.76 years of age and female

workers have on average of 30.80 years of age.

Figure 2. Employees’ average age in the Metal Mechanic Sector

Number of Employees

female14 %

male86 %

Average Age

female30.80

male29.76



4.1.3 Average Seniority of employees

Figure 3 shows that the average seniority of male workers is 6.79 years while female workers

have average seniority of 4.03 years. This results show also that male gender is still being

preferable above female gender in these companies.

Figure 3. Average seniority in the Metal Mechanical Sector

4.1.4 Equipment Used in the Metal Mechanical Sector Companies

Participating companies present a variety of equipment. Equipment was classified into seven

categories according to the manufacturing purpose: CNC Technology, Cutting Technology,

Traditional Technology, Molding of Plastic Technology, Cleaning and Treatment of Metals

Technology, Welding Technology, and Others.

As it is shown in Figure 4, actually CNC Technology is almost as frequent to find as

traditional Technology. Finally, a growing trend can be observed on equipment such as electrical

discharge machines, flexible manufacturing cells, robots, robo-drills, and progressive die press

found in the Others classification.

25

642721

161

12

160

0

20

40

60

80

100

120

140

160

180

CNCTec hnology

CuttingTec hnology

TraditionalTec hnology

Molding ofPlas tic s

Tec hnology

Cleaningand

Treatmentof Metals

Tec hnology

WeldingTec hnology

Others

Figure 4. Classification of the Equipment Used in the companies

Average Seniority

female4.03

male6.79



4.2 Important Characteristics of the Selection Processes for AMT acquisition. This section shows the results of some characteristics of the planning and selection processes

found in these companies. 4.2.1 Planning Processes for the acquisition of AMT in the Industry

Figure 5 shows that 77 % of the companies surveyed do perform some kind of planning processes

for the acquisition of AMT; this indicates the relevance of a good decision making about AMT.

Companies that do perform Planning Processes for AMT

23 %NO

77 %Y E S

Figure 5. Percentage of Companies that do perform Planning Processes for AMT acquisition

In these companies, the planning processes performed for AMT acquisition are mainly part of

engineering projects; this means that projects play an important role due to the specifications

accomplishment on the selection of AMT. Also, in most of these companies the planning

processes are executed only by the high management. Figure 6 shows the kind of personnel

involved in the planning process for the acquisition of AMT.

7

24

10

4

0

2

4

6

8

10

12

ManagementG roup

S es s ions

E ngineeringP rojec t

P lanning

Upgrade ofE quipment

R equirements

P roc es sE xec uted byC orporativeP ers onnel

P roc es sE xec uted by

HighManagemet

Figure 6. Planning Process Execution for AMT acquisition

Figure 7 shows that Executive and Administrative Personnel are mainly involved in the planning

and selection processes; also in 35 % of the companies a group composed by executive,

administrative and operative personnel conduct the decision for AMT acquisition.



41 %

17 %7 %

35 % E xec utive pers onnel

A dminis trative pers onnel

Operative pers onnel

A group of the three

Figure 7. Personnel who participate on the Planning Process for AMT acquisition

Companies have different search methods for acquiring AMT. Some companies use two or three

of this methods at the same time. Figure 8 shows that the use of internet web service and vendors

casting are the most extended ways for search and acquire AMT, followed by benchmarking and

equipment’s exhibit. Also the use empirical knowledge is included in the Others category.

98

18

7

13

0

2

4

6

8

10

12

14

16

18

20

V endorsC as ting

E quipment'sE xhibit

Internet WebS ervice

B enc hmarking O thers

Figure 8. Searching Methods for AMT acquisition

4.2.2 Application of Evaluation Processes for the selection of AMT

Once the AMT has been identified, it is recommended to perform some kind of diagnosis

processes to ensure that company’s expectations are met and avoid high costs. Figure 9 shows

most of the companies do perform some kind of evaluation or diagnosis processes for AMT

selection.

Figure 9. Companies that perform some kind of evaluation

Among these companies, the processes are supported by experts in the first place; then by the

use of checklists and standardized corporative formats, only a few use some specialized software;

and one company uses only the experience (Figure 10). Companies that omit evaluation

processes assume that the requirements are included by default in the equipment.

Companies that perform some kindof evaluation

20 %NO

80 %YES



13

7

18

89

0

2

4

6

8

10

12

14

16

18

20

V endorsC as ting

E quipment'sE xhibit

Internet WebS ervic e

B enchmarking Others

Figure 10. Diagnosis Methods for the selection of AMT in the Metal Mechanic Sector

These results show that most companies recur to experts to enhance their decisions.

4.2.3 Ergonomic Attributes on the Planning Process

Figure 11 shows that slightly more than a half of the surveyed companies that do apply some kind

of evaluation process also consider ergonomic attributes on the selection of AMT. It is inferred by

the attitude shown by managers and DM during interviews that 45% of them are unaware of the

ergonomic attributes that may be involved in the evaluation, even some of them had not even

heard about the topic.

Ergonomic Attributes on the Planning Process

45%NO

55%Y E S

Figure 11. Ergonomic Attributes on the Planning Process

Ergonomic attributes included in the diagnoses of the equipment were diverse, but it was

emphasized that all managers are looking for comfort for their operative personnel through proper

postures and less effort. It was also important for managers the adjustability of the equipment.

Additionally, usability of the equipment is required since they look for easiness of use in

equipment and tools, also, Compatibility with Human Skills and Training seems to be the most

important ergonomic attributes for DM on the selection of AMT according to Maldonado (2009).

About DM who do not consider ergonomic attributes in the diagnoses, they argue that the priority

on AMT must be on the technical aspects, costs and lead times. Also the main reason to do so is

the lack of knowledge about Ergonomics and the need of a pragmatic model or method that

facilitates their integration in decision making.



On the other hand, safety attributes are included in the evaluation processes in almost all

companies. Among the 30 companies surveyed, only one refused to include safety attributes in

the diagnosis. Figure 12 shows this fact. It is deduced that safety attributes are much better known

than Ergonomic Attributes among DM.

Safety Attributes on the Planning Process

97%Y E S

3%NO

Figure 12. Safety Attributes on the Planning Process

In this research, most of the companies recognized that the integration of ergonomic attributes

can become a strategic advantage for competitiveness; and for DM the combination of

ergonomics and safety attributes would enhance the implementation of AMT, therefore it is easier

to derive the benefits that both aspects generate. Figure 13 shows this fact.

Companies that consider Ergonomics

and Safety attributes help to a best implementation of AMT

83 %Y E S

17 %NO

Figure 13. Companies that find a strategic advantage of Ergonomics

5. CONCLUSIONS AND RECOMMENDATIONS It can be concluded that most companies surveyed do perform some kind of planning and

selection processes for AMT acquisition. However, the integration of ergonomic and safety

attributes are usually neglected in the diagnosis and selection processes for acquiring AMT. The

final decision about AMT acquisition is lead by the high management personnel and is strongly

supported by experts. It was found appropriate by DM to increase their knowledge about the

ergonomics aspects that can be taken into account to support their decision due to they consider

Ergonomic and Safety attribute as a strategic advantage. The AMT which predominate in the



Metal Mechanic Sector in Juarez, Mexico has gradually been replacing traditional technology.

Different practices for decision making about AMT among companies were studied, making clear

that engineering projects are one of the most important reasons to replace or acquire equipment.

Finally, it was analyzed the methods used by companies to identify and search AMT, where the

internet web service was the method preferred by DM due to its convenience.

It is recommended to extend this study among macro enterprises which have higher occupation

and may have records of accidents, injuries, days away from work and other events related with

the operation of AMT. This may help to obtain more accurate results of the importance of the

integration of ergonomic attributes on the selection of AMT.

6. REFERENCES Corlett E. N. y Clark T.S. (1995). The Ergonomics of Workspaces and Machines, 2a. Edición,

Taylor and Francis. European Agency for Safety and Health. 2007. “Work ILO Facts European Agency for Safety and

Health at Work”, http://www.ilo.org/public/english/standards/relm/ilc/ilc90/pdf/rep-v-1.pdf. Helander, M. (2006). A guide to human factors and ergonomics, 2nd Edition, Taylor & Francis

Group, pp. 8. IMSS. 2007. “Estadísticas laborales del Instituto Mexicano del Seguro Social”,

http://www.siicyt.gob.mx/siicyt/Principal.do?urlc=4,14. Karwowski W. 1990. “Injury control and worker safety in integrated manufacturing systems”,

Unpublished Technical Report, Center for Industrial Ergonomics, University of Louisville, Louisville, Kentucky, United Sates of America.

Karwowski W. 2005. “Ergonomics and human factors: the paradigms for science, engineering, design, technology and management of human-compatible systems1”, Ergonomics, Vol.48, No. 5, Pgs. 436-463.

Karwowski, W., Parsaei, H.R., Nash, D.L., and Rahimi, M. (1988). Human perception of the work envelope of an industrial robot, in Ergonomics of Hybrid Automated Systems, W. Karwowski, H. R. Parsaei, and M. R. Wilhem, Eds., Elsevier, Amsterdam, pp. 421-428.

Karwowski, W. and Salvendy, G. (2006). Handbook of human factors and ergonomics, John Wiley & Sons Inc., United States of America.

Labour and Social trends in Asean. 2007. “Labour and Social trends in Asean countries”,http://www.ilo.org/public/english/region/asro/bangkok/library/download/pub07-04.pdf.

Maldonado Macías Aide Aracely, (2009). Tesis Doctoral, Instituto Tecnológico de Cd. Juárez. Diciembre 2009.

Maldonado Aide, Noriega Salvador, Díaz Juan J., (2009). Ergonomic Compatibility Survey for the Evaluation of Advanced Manufacturing Technology, Proceedings of the International Safety and Occupational Ergonomics Conference.



Nicolaisen. P. (1985). Occupational safety and industrial robots-present stage of discussion within the tripartite Group on robotic safety, in Robot Technology and Applications,-Proceedings of the 1st Robotics Europe Conference, Brussels June 27-28, 1984, K. Rathmill, P. MacConaill, S. O’Leary, and J. Brown, Eds., Springer-Verlag, Berlin, pp. 74-89.

Prado León, L. (2001). Ergonomía y Lumbalgias ocupacionales. Sugimoto, N., and Kawaguchi, K. (1985). Fault-tree analysis of hazards created by robots, in

Robot Safety, M. C. Bonney and Y.F. Yong, Eds, Spreinger-Verlag, KFS, Berlin, pgs.83-98. U. S. Bureau of Labor Statistics. 2005. “Survey Occupational Injuries and Illnesse Summary

Estimates Package (Appendix B)”.



Remote Ergonomics Evaluations in the Office

Jeffrey E. Fernandez1, Gabriel Ibarra-Mejia 2, and Brandy F. Ware1

1JFAssociates, Inc Vienna, VA 22181

Corresponding author’s email: [email protected]

2 University of Texas at El Paso Department of Public Health Sciences

College of Health Sciences El Paso, TX

Resumen: Existe una prevalencia de trastornos musculo-esqueléticos, tales como el Síndrome

del Túnel de Carpo en el medio ambiente de oficinas, debido a la presencia de factores de riesgo

de lesión. Muy a menudo, los factores causales de incomodidad pueden ser detectados a través

de una evaluación del lugar de trabajo realizada por un individuo calificado, como lo es un

ergonomista. Gran cantidad de compañía y empresas no cuentan el personal con la experiencia

para realizar estas evaluaciones en forma interna, de tal manera que recurren a contratar

ergonomistas calificados. El creciente uso de la tecnología disponible en los lugares de trabajo y

la disminución de tiempos de entrega al realizar evaluaciones de lugares de trabajo, ha producido

que el ergonomista adopte nuevos abordajes para la solución de problemas relacionados con la

ergonomía. Este documento plantea la aplicación de evaluaciones ergonómicas de oficina

realizada a distancia (remotas) a través de un ergonomista virtual.

Abstract: In the office environment, musculoskeletal disorders such as carpal tunnel syndrome

are prevalent due the presence of injury risk factors. More often than not, the factors causing

discomfort can be accessed through a workplace evaluation performed by a qualified individual,

such as an ergonomist. Many companies do not have the expertise to conduct evaluations in-

house and hire a qualified ergonomist. The increasing use of enabling technology in the workplace

and shrinking delivery times for workplace evaluations has necessitated that ergonomists adopt

new approach to solving ergonomics related problems. This paper discusses the application of

remote ergonomic evaluations of office workstations through a virtual ergonomist.

Keywords: ergonomic evaluation, remote, office ergonomics



1. BACKGROUND

The repetitive nature of office work (long term keyboard and mouse use) or inappropriately

adjusted office equipment (i.e. chair and desk) could cause discomfort or injuries. Injuries often

begin as discomfort and are caused by exposure over a period of time to the repetitive nature of

work (long term keyboard and mouse use) or inappropriately adjusted equipment (i.e. chair and

desk). More often than not, the factors causing discomfort can be accessed through a workplace

evaluation performed by a qualified individual, such as an ergonomist.

When the ergonomist visits the workplace, he/she interviews the client, collects

measurements of the client and workplace, and makes recommendations. During the on-site

evaluation, the client must host the ergonomist by meeting them, escorting them to their work

area, and spending undivided attention while the ergonomist is there. This time away from their

work decreases productivity. From the ergonomist’s perspective, there is time spent commuting,

and collecting measurements at the workplace. In both of these cases, the cost is transferred to

the client. The speed of business today leads clients to expect a shorter delivery time for the

evaluations. Due to these factors, there is a need for a cost effective approach to solving office

ergonomics related problems.

One approach is to provide ergonomic evaluations through a virtual ergonomist (i.e. not on-

site). The evaluation is initiated by client contacting the service provider and concludes with the

virtual ergonomist following up with the client after recommending the necessary modifications.

This paper outlines the process employed by a virtual ergonomist for conducting an ergonomic

evaluation of an office workstation.

2. PROCESS AND DISCUSSION

The evaluation of the workstation includes all of the same basic elements of an in-person

evaluation along with the same deliverables. This process was initially implemented in paper /

electronic form using email for data transfer. The evaluation process flow is shown in Figure 1.



The first stage of the process is the initial contact with the client. The assessment sequence

is generally triggered an employee or other individual (e.g. health services, management)

requesting an evaluation of the workstation in response to a perceived issue such as discomfort or

pain (reactive).

The next stage includes obtaining background information, workstation and anthropometric

measurements (as shown in a pictorial diagram that is provided), body part discomfort rating, and

digital data from the client. The still photos and /or video clips of the work area and the activities

being performed is the additional piece of data that is critical to the successful completion of a

remote ergonomics evaluation. The still images should be of the client in their work environment

simulating work tasks from different angles and locations to adequately demonstrate the postures

obtained during work. When possible, video footage should also be obtained of the real-time

performance of work (or simulated work) to demonstrate frequency information. A good rule of

thumb is that video data should be 5-10 minutes in length and include all significant tasks

performed by the client.

During the time the ergonomist reviews the data provided by the client, there might be a need

to contact the client to clarify or obtain more information about the discomfort, tasks, or

workstation setup. During the evaluation, at least three opportunities for information exchange via

phone call or video conference should be provided. The initial interaction should be to clarify the

initial background information provided and educate the client on proper ergonomic setup. The

second interaction should be to review the work related risk factors identified through the

evaluation. At this time, the ergonomist will review the recommendations and discuss possible

options for modification to a setup. The third interaction should occur after the workstation

modifications have been made by the client. This interaction may be visual (e.g. include photos or

video) in addition to verbal. This final stage of the evaluation is a very important element of the

process. A follow-up is essential to ensure that the end-user neither experiences any discomforts

similar to the ones before the workstation modification nor does he/she develop any additional

discomforts. At this time, the virtual ergonomist reviews the worksite for completeness of the

recommendations and to ensure that no other risk factors are present. Additional follows may be

scheduled as per need.



The output of a remote ergonomic evaluation will be very similar to those generated with a

traditional, on-site evaluation. The output in a written report should include a review of the current

status, a listing of the observed risk factors, and a list of recommended changes both short term

and long term.

Figure 1. Process Flow for an Ergonomic Office Evaluation through Virtual Ergonomist (Fernandez

et. al, 2009)



A remote system requires an understanding of the information needed, comprehensive

mastery of the fundamental office ergonomics principles and their application, and an appropriate

interpretation of the data provided by client. In most cases, only a certified and qualified

ergonomist(s) is an appropriate choice for these evaluations. The affect of such remote

evaluations could save clients money, decrease carbon footprint, and improve the transfer of

ergonomic information to remote locations.

The most advanced application of a virtual ergonomist involves the use of the internet as a

platform for providing the aforementioned services. A website with interactive screens is required

to solicit information. Additionally, the website should provide the user with the capability to upload

pictures and videos for review. The interactive screens of the web site should parallel the flow of

the remote evaluation.

3. TESTING AND IMPLEMENTATION

This process has been tested in the U.S. A. and Mexico. The testing involved the

participation of clients in the same manner as the end product was intended. Throughout the

testing, input was received on the nature of the questions that were asked and the

appropriateness of the directions given. As a result of the testing, refinements were made to the

processes and checklists to improve usability and ensure comprehensive collection of relevant

data.

4. REFERENCES

Fernandez, J.E., Ware, B.F., Kumar, A., and Subramanian, A. (2009). Office Ergonomics

Assessment Through Virtual Ergonomist. Proceedings of the 14th International Conference

on Industrial Engineering, Theory, Applications and Practice. Anaheim, CA.



COMPARATIVE ANALYSIS BETWEEN AN ERGONOMIC EVALUATION AND THE USERS' SATISFACTION OF NEW EDUCATIONAL CENTERS

B.Eng. Martín Daniel Del Sol Rangel1, M.Eng. Manuel Sandoval Delgado2

POSTGRADUATE DEPARTMENT AND INVESTIGATION

INSTITUTO TECNOLÓGICO DE HERMOSILLO

Tecnológico Ave. And Periférico Poniente Blvd, Sahuaro

HERMOSILLO, SONORA, 83170

[email protected], [email protected]

1 INTRODUCTION

Globalization is transforming all the products in comfort, while clients, current or potential, are

constantly increasing demands and expectations, products seemed fine yesterday, today may not

be satisfactory, it is then that to win and retain customers, organizations need to find something to

turn into a competitive advantage, that element is the quality. All organization looking to be more

competent and always at the forefront, offering the best to its customers and users, resulting in a

successful project.

The managing a project involves the application of knowledge, skills, tools, and techniques to

project activities so that they meet or exceed the needs and expectations of the stakeholders of a

project. The factors for the success of the project are the set of circumstances, facts, or influences

which contribute to the project results. The success of the projects we perceive from two

approaches, one micro which is represented by the cost, delivery time and meet customer

specifications, the other is the macro that represents the total satisfaction of the user who uses it.



The present work of investigation is a comparative analysis between studies of "Verification of the

environmental conditions in the facilities design of new buildings at the preschool level creation in

the education sector in Hermosillo, Sonora" and "Anthropometry and verification of facilities design

buildings at the preschool level ups in the education sector in Hermosillo, Sonora”, against the

results of the study “Factors influencing the satisfaction of user of schools newly created basic

level in Hermosillo, Sonora ", There are no studies that serve as background or base for departure

because it is a recent project of the Sonora Institute for Educational Infrastructure, which reports

to the State Government and which has never measured the satisfaction of users of such works

public.

2 OBJECTIVES

Making a comparison between the perceptions of the user against the measurements obtained in

the two studies mentioned above, concurrent, and find out if its result compared with the official

standards and anthropometric measures for installations in schools, have a value of significance

in user satisfaction. Be conducted only in the municipality of Hermosillo, Sonora, in the four

schools of this type found in the city.

3 METHODS

Was determined primarily based sample, in this case 32 which is the total of people working in

these institutions, being interviewed teachers, administrative and support, were interviewed by

school staff, as direct users , to hear his perspective from the macro environment, as well as



some people working in the Sonora Institute of Educational Infrastructure to meet their

expectations of the quality they deliver these works, that is, from the micro environment, with

this design A pilot survey to discover the needs or problems that arose within those premises

was a validation of the survey was applied in only one school, and was designed to be

analyzed a survey based on certain items required for research using the method Servqual,

which defines service quality as the difference between actual perceptions by users and is a

multi-scale instrument that has a high level of reliability and validity, that any organization can

use to better understand the expectations and perceptions about service users. The model

includes two dimensions of expectations: expectations desired (which I'd like in ideal terms)

and appropriate expectations (the acceptable level of service expected). Besides this is divided

into headings such as, visual perception and environmental design, ambient conditions, safety,

and responsiveness in terms of failures and complaints in the facility.

Thus, a survey was designed to apply well-defined in the entire field of study, ie, universal primary

education schools and kindergartens in the newly created municipality of Hermosillo.

Respondents were only administrative and teaching staff, these being the ability to direct users to

answer the survey because students are also users but do not have the maturity to respond

coherently to the research questions.

4 RESULTS

In implementing the surveys, we will realize the factors that influence the level of satisfaction of

users of each of these schools, we can compare each of them, finding differences and similarities

between themselves and in turn, and by type of primary or preschool, and thus may provide



feedback to those implementing this project, and be able to carry not only the success of the micro

environment but also from the macro. As well as we can compare these plots obtained in the

surveys carried out against the measurements obtained in the other two parallel research this and

see whether they comply with official standards, and then be detected if it affects the user

satisfaction.

The question 6, is related to the lighting of the classroom, if considered appropriate for the proper

performance of students and teachers, including the cataloged in the case of kindergarten as

excellent and as good in the Elementary School, giving it a rating 10 and 8 respectively. Here we

Figure 1. Results obtained in the survey research, “Factors are influencing the satisfaction of users of schools newly created basic level in Hermosillo, Sonora”, in the Kindergarten “Los Arroyos”.

Figure 2. Results obtained in the survey research, “Factors are influencing the satisfaction of users of schools newly created basic level in Hermosillo, Sonora”, in the Elementary School “Los Arroyos”.



see the data in the study of "Verification of environmental conditions in the facility design of the

buildings at the preschool level ups in the education sector in Hermosillo, Sonora."

The minimum level of lighting according to the NOM 025 analyzed, the minimum standard of this

factor must be 300 (lux) for the elderly, it is important to note that the measurement gives us a

number below this value. This result gives justification to change the lighting to classify it as only

good with an 8 on a scale of 5-10. The questioning in July, is related to the temperature of the

room, if it is deemed for the good performance of pupils and teachers, cataloged them both in

Kindergarten and Primary School under 8, or Regular. Here we see the data in the study of

“Verification of environmental conditions in the facility design of the buildings at the preschool level

ups in the education sector in Hermosillo, Sonora”.

Table 1. Results obtained in the ergonomic study research “Verification of environmental conditions in the facility design of the buildings at the preschool level ups in the education sector in Hermosillo, Sonora” in Kindergarten “Los Arroyos”.



The INIFED says that the environmental conditions that are suitable for work in comfort in the

case of classrooms are 18 to 25 degrees Celsius and can see that this condition is not met, most

of the measurements exceeds 25 degrees Celsius. Therefore, find out why the temperature is

listed as fair, although the results reflected rather as bad. As for the results of the investigation

"Anthropometry and verification of plant design of the buildings at the preschool level ups in the

education sector in Hermosillo, Sonora" was against a comparative study and survey of the results

were similar furnishings and facilities and equipment not designed for the good performance of

students mainly, not based on anthropometric tables according to your needs.

Thus, these results will support this project to strengthen Sonora School, offer these areas of

opportunity for improvement in those who develop, ie, the Sonora Institute of Educational

Infrastructure and also propose a concurrent engineering work, where without participation of all

Table 2. Results obtained in the ergonomic study research “Verification of environmental conditions in the facility design of the buildings at the preschool level ups in the education sector in Hermosillo, Sonora” in Kindergarten “Los Arroyos”.



stakeholders, including of course, users who guarantee from a macro perspective, the success of

our project.

REFERENCES

1. Cavassa Cesar Ramirez, Ergonomics and Productivity (2006), Cesar Ramirez Cavassa. - 2nd.

Ed - Mexico: Limusa, Chapter 8 Ergonomics and working environment.

2. Evan Lindsay (2000), Management and Quality Control, Ed Thompson 2000.

3. Evaluación.pdf

http://www.inifed.gob.mx/NORMASTÉCNICAS/VOLUMENTomo20PlaneaciónProgramaci

óny

4. Francis Quintero (2010) "Verification of environmental conditions in the facility design of the

buildings at the preschool level ups in the education sector in Hermosillo, Sonora."

5. Hiram Higuera (2010) Anthropometry and verification of plant design of the buildings at the

preschool level ups in the education sector in Hermosillo, Sonora. "

6. Julius Panero (1993), The human dimensions indoors, Ed G. Gili, SA., Mexico, D.F., pp. 23.

7. C. S. Lim and M. Mohamed Zain (1999) "Criteria of project success: an Exploratory re-

examination", International Journal of Project Management Vol 17, No. 4, Great Britain,

pp. 243-248.

8. O terminal, David J. (1990), Ergonomics in action: adaptation in the working environment of

man. - 2nd edition - Mexico: Trillas, (reprint 2007).

9. Roberto Hernandez Sampieri (1998) Research Methodology, Ed McGraw-Hill.

10. Standardization of the STPS, www.stps.gob.mx

11. Ted Klastorin (2008) Project management. Alfaomega Group Editor. Mexico City, Mexico. 242

pages.



DESIGN AND IMPLEMENTATION OF MANUFACTURING CELL WITH ERGONOMIC SUPPORT ANALYSIS

MC. Rigoberto Zamora Alarcón1, Ing. Manuel Enrique Alcaráz Ayala2,

MC. Julio César Romero González3

1Ingenieria Mecánica-Industrial Universidad Autónoma de Baja California-Instituto Tecnológico de Mexicali

Blvd. Benito Juárez S/N Mexicali, Baja California 21100

[email protected] 2Ingeniero de Manufactura ambiental

Consultor Independiente Mexicali, Baja California

[email protected] 3Ingeniero de manufactura y proyectos

Instituto Tecnológico de Mexicali Mexicali, Baja California

[email protected]

Resumen: Este estudio muestra el desarrollo del proyecto desde la perspectiva general del

análisis de riesgo ergonómico utilizando el método RULA (Rapid Upper Limb Assessment). El

análisis arrojo información para mejorar el ambiente de trabajo. Se desarrollo el Proyecto de

evaluación ergonómica en una compañía metalmecánica con más de 16 años en Mexicali, con el

propósito de enfocar esfuerzos en la prevención de riesgos ergonómicos.

El proyecto se apoyo en las características retrospectivas (5 años) de los registros médicos,

evidenciando lesiones músculo tendinosas en muñecas en las áreas de trabajo de ensamble,

específicamente en una estación en particular; los cuales fueron determinantes para definir el

proyecto en las celdas de manufactura.

Objetivo: Reconocer evaluar y controlar los riesgos laborales por actividades repetitivas,

posturas, y agentes del medio que por sus características puedan causar daños a la salud,

considerado el análisis ergonómico aplicado al concepto de celdas de manufactura

Metodología empleada: Normas oficiales Mexicanas de STPS (Secretaria de Trabajo y

Previsión Social) vigentes, Evaluación RULA/BRIEF, Mediciones antropométricas, Principios de

celdas de manufactura



Resultados

Tabla 1 Resultados del proyecto Mejora en Índice de frecuenciaTendinitis 95% Dolor de cuello 100%Espalda 90%

Beneficio Rotación de personal 0% Desperdicio -33% Optimización de espacio 40% Productividad 40%

Condiciones ambientales Iluminación 100%Ruido 100%

Conclusiones: Con base a los datos obtenidos:

Disminuyo el índice de frecuencia de lesiones por tendinitis, dolor de cuello y espalda;

impactando de manera favorable la rotación

Se considerarán para el diseño de las estaciones de trabajo, la media poblacional del estudio

antropométrico

Se comprobó que el costo beneficio de la aplicación de la ergonomía generó mejoras

significativas en las condiciones laborales beneficiando a casi 500 empleados

Palabras Clave: Celdas de manufactura, RULA, Análisis Ergonómico

Abstract: This study shows the project's general perspective for ergonomic hazards using the

RULA’s (Rapid Upper Limb Assessment) method. Analysis shows information to improve the work

environment. Project ergonomics was developed in a metalworking company with over 16 years in

Mexicali, with the proposed of focusing efforts on preventing ergonomic risk.

The project was supported in retrospective characteristics (5 year) medical records, which showed

muscle lesions in wrist tendon (CTD: Cumulative Trauma Disorder) areas specifically assembly

work at a particular station, were decisive in defining the project in manufacturing cell.



Objectives: Recognize asses and control the labor risks for repetitive activities, postures, and

environmental agents that have certain characteristics may cause damage to health, considered

the ergonomic analysis applied to the concept of manufacturing cells.

Used methodology: Mexican official standards of existing STPS (Secretaria de Trabajo y

Previsión Social), RULA Assessment, Anthropometric measurements and Principles of

manufacturing cells.

Results:

Table 1 Project results Improved Frequency index

Tendinitis 95% Neck pain 100%

Back and shoulders 90% Benefits

Absenteeism 0% Waste -33%

Space optimization 40% Productivity 40%

Environmental conditions Ilumination 100%

Noise 100% Conclusions: Based on the data:

Reduce the frequency index of tendinitis injuries, neck and back pain, favorably impacting the

absenteeism.

Will be considered for the design of workstations, the population mean anthropometric study.

It was found that the cost benefit of the application of ergonomics to yield significant

improvements in working conditions, benefiting nearly 500 employees.

keywords. Manufacturing cells, RULA and Ergonomic Analysis

1.- INTRODUCTION

This study shows some of the environmental factors of process redesign in a metalworking

company with over 16 years in Mexicali, initiating the development of the project from the overall



perspective of ergonomic risk analysis methods using RULA (Rapid Upper Limb Assessment) /

BRIEF. The analysis yields information to improve the working environment, in order to focus

efforts on preventing ergonomic hazards.

The project will support the features retrospectives (five years) of medical records, showing

muscle tendon in wrist injuries in the assembly work areas, specifically in a particular season,

which were crucial in defining the project in the cells manufacturing.

Later it was necessary to implement each of the principles of manufacturing cells, which had as

one of its aims to cut down injuries sustained when production lines were used and the

advantages that the implementation of this system of manufacturing production in its approach .

It was remarkable to observe that first applied the standards and principles Japanese and

Mexican Americans than the standards established by federal labor law.

2.- Objective

Recognize evaluate and control occupational hazards by repetitive activities, postures, and

environmental agents which by its nature could cause damage to health, considered the

ergonomic analysis applied to the concept of manufacturing cells

3. Methodology 3.1. Factors and Design Techniques

To develop improvements as a project in newly created department was required to first

determine the factors necessary in a process or product improvement, further weighting. Factors

that were discussed and were weighted were: packaging, ergonomics, reliability, maintenance,

manufacturing, environment, performance and safety. Of the above factors stood out in his group,

ergonomics and manufacturing, which were diagnosed as other such systems and subsystems as

corresponded in the following items on this article.

3.1.1 Weight and diagnostic medical. To be able to support the weight of the plant physician, was

necessary to make a diagnosis of injuries in the last 5 years behavior which is shown in Figure 1.



Figure 1. Injury graphic in the last five years in the production line

As can be seen from the graph in Figure 1, tendinitis injuries were the most frequently expressed,

in analyzing the documents supporting the physician receives a particular station as the main

carrier of the injury. It was decided to take a more precise analysis of the case which had

previously been tested ergonomically down significantly, however, the cases have involved the

previous year that operators avoid working in the station. The weighting is determined whether

one could know if our proposals were significant in their environment, it was necessary for the

same thermal analysis on a ship operated blade in a municipality that maintains extreme

temperatures in the year. Realising the study as shown in Figure 2, the tendinitis was found

increased in the months where the heat is great in Mexicali.

Figure 2. Tendinitis injury in the last five years



3.2. Mexican Official Standards of STPS (Secretary of Labor and Social Welfare) in force Federal

Labor Law art. 132 Obligations of Employers Cap. X, Ergonomics art. 102. (Federal Regulation on

Safety, Hygiene and Working Environment 1997)

The official Mexican standards determined by the Secretary of Labor and Social Welfare in effect

allowed us to measure each of the parameters set by physical and chemical conditions, however,

to labor issues in the area we focus on the chemical physics but also evaluated

3.2.1 Physical

Vibrations (NOM-024-STPS-2001),

Noise (NOM-011 - STPS-2001). Concentration equivalent dB (A): continuous, intermittent,

fluctuating and Impact,

Lighting (NOM-025-STPS-1999)

a) Disposition: General, located, and auxiliary

b) Artificial: Incandescent, fluorescent, vapor and H

c) Natural

d) Combined

Radiation

a) Ionizing (NOM-012-STPS-1999) x-rays, radioisotope and other

b) Non-ionizing (NOM-013-STPS-1993), ultraviolet, infrared, radio frequency and other static

Electricity (NOM-022-STPS-1999)

Thermal conditions (NOM-015-STPS-2001)

3.2.2 Chemicals

Substance (NOM-010 - 1999 STPS-)

3.3. Anthropometric measurements

Some anthropometric measurements of operators are working in the plant are shown in Table 1



Table 1 Some anthropometric measurements of line operators

3.4. RULA Assessment / BRIEF

Poor posture is considered one that moves away from a neutral position or physiological, where

they play an important role while maintaining the posture and the handling of heavy objects.

(Kroemer 2000). Since the results were assessed at the station representing more problems in

production lines using the method as the main tool right RULA showed results that could be

considered in the design of new stations. First results were deciphered on the right of operators to

both women and men as shown in Figure 3 where we obtained the results of urgent change of

season.

3.5 Principles of manufacturing cells (Villaseñor 2009)

1. Place machines and workstations as close as possible to minimize the distance to be walking

2. Free from obstructions routes and install comfortable floor worker

Increase the safety of workers

Improved productivity

Greater flexibility of work for each operator

2. Keep the cell width of 4 feet to allow flexibility, relocation and redistribution of work among team

members

Minimize distances of each operator

Operators have access to both sides of the cell

Increases the flexibility of the work cycle, so there may be operating on both sides of the

cell U



Figure 3. RULA Evaluation for production line (belt) 4. Heights consistently maintain places of work and materials at the point of use

5. Locate the end of the line as close as possible to the next line.

6. Avoid carrying a piece of top-down and front-back

Always avoid placing the parts manufactured in shelves, racks, boxes or any container that is

out of the process

7. Where possible, use gravity to assist the operator in the placement and movement of materials



8. Design a system of two containers refill

9. Install flexible and movable equipment in the cell distribution to fit easily

Facilitates continuous improvement efforts, reduce time and costs for the relocation of

production in cells

Improve response times to changes in products or processes

8. Manufacturing cell design for flexibility of volume

a. Flexibility:

b. Design assembly line layout to cellular manufacturing in a "U" or "U" open.

c. Eliminate communication barriers and increase teamwork

9. Minimize the distance between operations transfer

10. Cycle times operator must be at or below the target time / takt

a. Ensure that the cell meets the customer demand time

b. Ensures that meets the capacity requirements

13. Design routes operating within the cell, making sure not cross

a. Increases operator safety

b. Facilitates flow of material

c. Optimize productivity by removing obstacles from the path

d. Ensures follow-up sequence of work

14. Design the cells for operators to work within it.

a. Promotes communication and teamwork

b. Improved response time and operating in several machines or workstations

c. Optimize production space

d. Reduce travel distances

15. Design the cells so that the rotation of the work is against clockwise

a. Improved ergonomic design

b. Facilitates milestone

c. Standardize more material flow

d. Eliminate wasted movement when moving the product of the hand that receives the

working

16. Design the cells so that the operations are more than one piece among stations

a. Minimize WIP



b. Pull Production System or milestone

17. Design the cells to ensure that all parties go through all seasons

18. Design the cells so that the operator can easily perform various operations.

a. Helps to improve the ergonomic design by reducing repetitive movements

b. Improves mobility and versatility of workers

c. Allows greater flexibility

d. Promotes "system thinking", continuous improvement

e. Eliminate each operation specialists

f. Improved response time

g. Improved communication

h. Improved teamwork

i. Improving the skills of each to rotate the cell operations

19. Design the cells so that the operator never trapped

20. Better handling of material

a. Improving the response time

4. Results 4.1 Medical conditions for improved stations applied in manufacturing cells

Measurements after the improvements implemented in the stations of the manufacturing cells

reduce injuries allowed as shown in Figure 4

4.2. RULA assessment implemented in manufacturing cells. Improvements in manufacturing

cell stations were significant as shown below. First results on the right of operators to both

women and men shown in Figure 8 and Figure 9 where we obtained the results to changes in

tasks



Figure 4 raph of injuries sustained in the first year of cells

5. Conclusions: 6.

1. We complied with the standards prescribed by the current Mexican

2. Engineering controls were implemented through:

a) were improved work areas with more light,

b) decreased redesign of machinery noise

c) the use of workstations in the corresponding cells that fulfilled the relevant principles

d) Development of tools to reduce ergonomic hazards

e) Improved handling containers and material moving

3. Administrative Controls

• Work was rescheduled through the seasons in the manufacturing cell

• were established relaxation breaks that allow staff

4. Work practice controls

• is looking to keep the body in neutral positions

5. Based on the data obtained from the RULA ergonomic evaluation and implementation of

manufacturing cells



Figure 5 RULA evaluation in cell

a. Reduce the frequency rate of tendinitis injuries, neck and back pain, impacting favorably

rotation

b. be considered for the design of workstations, the population mean anthropometric study

c. It was found that the cost benefit of the application of ergonomics led to significant

improvements in working conditions, benefiting nearly 500 employees



5. REFERENCES

Kromer, Grand Jean E (2000) Fitting the task to the human. Taylor & Francis Villaseñor, Contreras Alberto (2009) Lean Manufacturing ed. Limusa Mexico, D.F. Ley Federeal del Trabajo y Leyes de Seguridad Social 2009 Tax Editores unidos, S.A de C.V. Mexico, D.F. Zandin, Manual del Ingeniero Industrial quinta edición, ed. McGraw-Hill Niebel/Frievalds (2006) Ingenieria Industrial, Métodos, Estándares y Diseño del Trabajo, 11ª Edición. (ed. Alfaomega) Mondelo, Pedro R, Gregori, Enrique, Blasco, Joan, Barran, Pedro (2004) Ergonomía 3 Diseño de puestos de Trabajo, Ed. Alfaomega Baudin, Michel (2001), Design of Manufacturing Cells.

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