Maximum voluntary forces and psychophysically acceptable forces are often used to set force guidelines for exertions as a means to protect against overexertion injuries in the workplace. The focus of this dissertation was the exploration of the roles of whole body balance, shoe-floor friction and joint strength in limiting the capacity of a person to produce maximum voluntary hand forces and psychophysically acceptable hand forces. The underlying goal was to advance knowledge regarding how physical exertion capacity is biomechanically governed, then to use this information to develop models to predict capability based on these governing principles. The hypothesis underscoring this work was that maximum voluntary hand force capability is governed by whole body balance, shoe-floor friction and joint strength; and consequently, psychophysically acceptable forces would be chosen proportionally to this maximum voluntary force capability, where the magnitude of the proportionality was dependent on the limiting factor, or ‘weakest link’. To investigate this hypothesis, both experimental and mathematical modeling paradigms were used. Initially, an experimental study was used to investigate how biomechanical factors governed maximum hand force capability across a range of exertions. It revealed that each governing factor differentially limited maximum force capability. Moreover, this study identified how foot placement, handle height, distance from the handle, friction, and body posture all influence the underlying biomechanical weakest link, and ultimately force producing capability. Data gathered in the experimental study was next used to evaluate a mathematical model that was developed to predict maximum force capability, given information on posture and direction of force application. In addition, the model also predicted population variability in maximum capacity based on the inclusion of a novel approach to probabilistically represent population variability. The evaluation demonstrated that the model underestimated maximum hand force capability compared to measured hand forces by approximately 18, 26, and 41% during medial, pulling and downward exertions respectively. However, it appeared that the ‘weakest link’ principle for predicting maximum force capacity was plausible, as evidenced by significant rank ordered correlations between the measured and predicted hand forces. Further research investigated if psychophysically acceptable forces were selected as a proportion of task specific maximum voluntary force capability, where the proportionality was related to the biomechanical weakest link. Using an experimental design, psychophysically acceptable forces and corresponding maximum forces were measured. Participants chose psychophysically acceptable forces that were 4/5ths of their task specific maximum voluntary force capability when capability was limited by balance. Additionally, they choose psychophysically acceptable forces that were 2/3rds of their maximum voluntary force capability when capability was limited by joint strength. The identification and confirmation of a weakest link proportionality principle represents an important contribution to the field of occupational biomechanics. The weakest link proportionality principle was integrated into the model to allow prediction of: maximum voluntary hand force capability, the limiting factor, and psychophysically acceptable hand force capability. The updated model underestimated empirically measured psychophysically acceptable forces by 24% and 43% during downward and pulling exertions respectively. However, the original model underestimated the maximum hand force capacity by 23% and 34% during the same exertions, without the proportional relationships. This underestimation may be a result of the underlying assumption that joint strength is independent, resulting in an underestimation of maximum joint strength capacity and a corresponding underestimation of maximum hand force capacity. The underestimation may also be due to differences in strength capacities between the participants tested during this thesis compared to those tested in past research used to determine the maximum strength indices reported in the literature. This body of work supported the hypothesis that psychophysically acceptable forces are selected as a proportion of the maximum voluntary hand force, where the proportionality depends on the underlying biomechanical weakest link. The model is a promising first step towards predicting maximum and psychophysically acceptable occupational force threshold limits.

Maximum voluntary forces and psychophysically acceptable forces are often used to set force guidelines for exertions as a means to protect against overexertion injuries in the workplace. The focus of this dissertation was the exploration of the roles of whole body balance, shoe-floor friction and joint strength in limiting the capacity of a person to produce maximum voluntary hand forces and psychophysically acceptable hand forces. The underlying goal was to advance knowledge regarding how physical exertion capacity is biomechanically governed, then to use this information to develop models to predict capability based on these governing principles. The hypothesis underscoring this work was that maximum voluntary hand force capability is governed by whole body balance, shoe-floor friction and joint strength; and consequently, psychophysically acceptable forces would be chosen proportionally to this maximum voluntary force capability, where the magnitude of the proportionality was dependent on the limiting factor, or ‘weakest link’. To investigate this hypothesis, both experimental and mathematical modeling paradigms were used. Initially, an experimental study was used to investigate how biomechanical factors governed maximum hand force capability across a range of exertions. It revealed that each governing factor differentially limited maximum force capability. Moreover, this study identified how foot placement, handle height, distance from the handle, friction, and body posture all influence the underlying biomechanical weakest link, and ultimately force producing capability. Data gathered in the experimental study was next used to evaluate a mathematical model that was developed to predict maximum force capability, given information on posture and direction of force application. In addition, the model also predicted population variability in maximum capacity based on the inclusion of a novel approach to probabilistically represent population variability. The evaluation demonstrated that the model underestimated maximum hand force capability compared to measured hand forces by approximately 18, 26, and 41% during medial, pulling and downward exertions respectively. However, it appeared that the ‘weakest link’ principle for predicting maximum force capacity was plausible, as evidenced by significant rank ordered correlations between the measured and predicted hand forces. Further research investigated if psychophysically acceptable forces were selected as a proportion of task specific maximum voluntary force capability, where the proportionality was related to the biomechanical weakest link. Using an experimental design, psychophysically acceptable forces and corresponding maximum forces were measured. Participants chose psychophysically acceptable forces that were 4/5ths of their task specific maximum voluntary force capability when capability was limited by balance. Additionally, they choose psychophysically acceptable forces that were 2/3rds of their maximum voluntary force capability when capability was limited by joint strength. The identification and confirmation of a weakest link proportionality principle represents an important contribution to the field of occupational biomechanics. The weakest link proportionality principle was integrated into the model to allow prediction of: maximum voluntary hand force capability, the limiting factor, and psychophysically acceptable hand force capability. The updated model underestimated empirically measured psychophysically acceptable forces by 24% and 43% during downward and pulling exertions respectively. However, the original model underestimated the maximum hand force capacity by 23% and 34% during the same exertions, without the proportional relationships. This underestimation may be a result of the underlying assumption that joint strength is independent, resulting in an underestimation of maximum joint strength capacity and a corresponding underestimation of maximum hand force capacity. The underestimation may also be due to differences in strength capacities between the participants tested during this thesis compared to those tested in past research used to determine the maximum strength indices reported in the literature. This body of work supported the hypothesis that psychophysically acceptable forces are selected as a proportion of the maximum voluntary hand force, where the proportionality depends on the underlying biomechanical weakest link. The model is a promising first step towards predicting maximum and psychophysically acceptable occupational force threshold limits.

Made available in DSpace on 2014-06-11T19:22:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-20Bitstream added on 2014-06-13T18:07:11Z : No. of bitstreams: 1 santos_ea_me_ilha.pdf: 1369014 bytes, checksum: 7ea566c05320b595e08fe89ae2170203 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O teste de força de aperto das mãos tem como finalidade detectar eventuais patologias nos membros superiores e avaliar a força exercida pelas mãos de pacientes. Neste trabalho é descrito o desenvolvimento de um dinamômetro biomédico projetado para efetuar a avaliação funcional das mãos, através da utilização de moldes específicos. O equipamento é constituído basicamente por sensores com extensômetros metálicos, um circuito de condicionamento de sinais, um circuito de interfaceamento e por um display digital. O circuito de condicionamento de sinais foi implementado com um amplificador de instrumentação, um amplificador com ganho programável e por um filtro passa-baixas. O principal componente do circuito de interfaceamento é o microcontrolador ATMEGA8. O equipamento é robusto, apresenta resposta linear na faixa de 0 a 500 N, precisão de 0,54%, resolução de 0,70 N e histerese desprezível. O valor da força pode ser lida em um display e também na tela de um computador. Pode ser útil em Engenharia de Reabilitação, Fisioterapia e Terapia Ocupacional / In this work we describe the development of a biomedical dynamometer. It was designed with the goal of performing the functional evaluation of hands with specific shapes. The equipment is constituted by force sensors, a signal conditioning circuit, an interface circuit and a digital display. Metallic strain gages were used as sensors. The signal conditioning circuit is constituted by an instrumentation amplifier, a programmable gain amplifier and a low-pass filter. The main component of the interface circuit is an ATMEGA8 microcontroller. The instrument can measure forces with resolution of 0.70 N and precision of 0.54% in the range of 0 to 500 N. It is rugged, presents linear response and very small hysteresis. The value of the force can be read in a display and in a computer screen. The device can be useful in Rehabilitation Engineering, Physiotherapy and Ocupational Therapy

Die ergonomische Anpassung von Produkten der körpernahen Umwelt an den menschlichen Körper in seiner gesamten Variabilität erfordert anthropometrische Grundlagen. Die vorliegende Arbeit beschreibt und analysiert die Körpermasse, 17 Längenmaße, 5 Skelettrobustizitätsmaße, 6 Korpulenzmaße, 3 Kopfmaße, 5 Handmaße, 3 Fußmaße, sowie 10 Beweglichkeitsmaße der Wirbelsäule, 8 Beweglichkeitsmaße der Hand, 2 Beweglichkeitsmaße des Beines und 7 Handkräfte von 295 Probanden der drei Altersgruppen 20 bis 29 Jahre, 50 bis 59 Jahre und 60 bis 69 Jahre. Die Untersuchungen wurden im Zeitraum von September 2006 bis April 2007 durchgeführt. Ziel der Arbeit ist es, für den überwiegenden Teil der untersuchten körperlichen Merkmale erstmals für die deutsche Bevölkerung geschlechts- und altersspezifische Mittelwerte und Variabilitätsbereiche bis zum vollendeten 70. Lebensjahr zur Verfügung zu stellen. Das gilt insbesondere für die untersuchten Beweglichkeitsmaße und Handkräfte. Erstmals werden Korrelationen zwischen der Körperform, wie sie sich im Maßzusammenhang der unterschiedlichen Körperbautypen darstellt, der Gelenkbeweglichkeit und den Handkräften vorgestellt. Darüber hinaus wird durch den Vergleich der Ergebnisse der jungen und der beiden älteren Erwachsenengruppen untersucht, welche Unterschiede zwischen den verschiedenen Altersgruppen bestehen. Im Hinblick auf die zeitliche Gültigkeit der aktuellen Untersuchungsergebnisse werden der Einfluss des säkularen Trends und der Einfluss der ontogenetischen Alternsprozesse auf Längenmaße und Korpulenzmaße diskutiert. Die Arbeit zeigt auf, dass innerhalb der untersuchten Probanden eine große Variationsbreite in den Körpermaßen auftritt. Es lassen sich typische Altersunterschiede erkennen. Die Älteren sind im Mittel kleiner, weisen jedoch größere Skelettrobustizitäts- und Korpulenzmaße auf. Die dynamischen Maße weisen auf eine geringere Beweglichkeit der Wirbelsäule, teilweise auch der Hand hin. Die Handkräfte der Frauen werden mit zunehmendem Alter geringer, bei den Männern sind die Älteren kräftiger als die jungen Erwachsenen. Die Ergebnisse deuten auf einen gegenüber früheren Generationen verzögerten Beginn von körperlichen Alterserscheinungen hin, der im Hinblick auf die steigende Lebenserwartung der Bevölkerung eingehender untersucht werden sollte. / The ergonomic adaptation of products of the body close environment to the human body in its whole variability requires an anthropometric basis. The present work describes and analyses the body weight, 17 longitudinal, 5 skeletal and 6 corpulence dimensions of the human body, 3 head dimensions, 5 hand measurements, 3 foot measurements, as well as 10 measurements of the mobility of the spine, 8 mobility measurements of the hand, 2 mobility measurements of the leg and 7 hand forces of 295 test persons of the three age groups 20 to 29 years, 50 to 59 years and 60 to 69 years. The investigations were carried out in the period from September 2006 to April 2007 in Wolfsburg and Potsdam, Germany. The aim of the work is to make available averages and variability areas specific for age and specific for men and women up to the 70th birthday for the German population. This is valid in particular for the examined mobility measurements and hand forces. For the first time correlations are introduced between different body types and joint mobility and hand forces. In addition, it is examined by the comparison of the results of the young ones and both older adult's groups which differences exist between the examined age groups. With regard to the temporal validity of the investigation results the influence of the secular trend and the influence of the ontogenetic ageing processes on longitudinal and corpulence dimensions of the human body are discussed. The work indicates that within the examined test persons a big variation width appears in body measurements. Typical age differences exist. The older people are smaller on average, nevertheless, they show bigger skeletal and corpulence dimensions. The dynamic measurements point to a lower mobility of the spine, partially also of the hand. The hand forces of the women become lower with increasing age. In men the older test persons are stronger than the young adults. The results point to a delayed beginning of physical signs of ageing compared to former generations.

Orientador: Aparecido Augusto de Carvalho / Banca: Alexandre César Rodrigues da Silva / Banca: Josivaldo Godoy da Silva / Resumo: O teste de força de aperto das mãos tem como finalidade detectar eventuais patologias nos membros superiores e avaliar a força exercida pelas mãos de pacientes. Neste trabalho é descrito o desenvolvimento de um dinamômetro biomédico projetado para efetuar a avaliação funcional das mãos, através da utilização de moldes específicos. O equipamento é constituído basicamente por sensores com extensômetros metálicos, um circuito de condicionamento de sinais, um circuito de interfaceamento e por um display digital. O circuito de condicionamento de sinais foi implementado com um amplificador de instrumentação, um amplificador com ganho programável e por um filtro passa-baixas. O principal componente do circuito de interfaceamento é o microcontrolador ATMEGA8. O equipamento é robusto, apresenta resposta linear na faixa de 0 a 500 N, precisão de 0,54%, resolução de 0,70 N e histerese desprezível. O valor da força pode ser lida em um display e também na tela de um computador. Pode ser útil em Engenharia de Reabilitação, Fisioterapia e Terapia Ocupacional / Abstract: In this work we describe the development of a biomedical dynamometer. It was designed with the goal of performing the functional evaluation of hands with specific shapes. The equipment is constituted by force sensors, a signal conditioning circuit, an interface circuit and a digital display. Metallic strain gages were used as sensors. The signal conditioning circuit is constituted by an instrumentation amplifier, a programmable gain amplifier and a low-pass filter. The main component of the interface circuit is an ATMEGA8 microcontroller. The instrument can measure forces with resolution of 0.70 N and precision of 0.54% in the range of 0 to 500 N. It is rugged, presents linear response and very small hysteresis. The value of the force can be read in a display and in a computer screen. The device can be useful in Rehabilitation Engineering, Physiotherapy and Ocupational Therapy / Mestre