The purposes of the present work were: 1) to develop a computerized model that could predict the personal lift-assist device (PLAD) spring excursion and control spring stiffness for various individuals based on their anthropometry and working posture and 2) to test the PLAD’s (Version 6) effectiveness and user acceptability during static forward bending in an automotive assembly plant. Study 1 required 30 subjects to carry out a protocol that simulated unloaded stoop, squat, and freestyle lifting. Trunk inclination and knee angles were determined via 3 FastrakTM sensors, whereas a displacement transducer attached in-line with the PLAD determined excursion when the trunk or knees flexed. A model was created to determine spring excursion, and it was successfully validated with 10 additional subjects. A computerized model applying the excursion model and mathematical equations was also developed to calculate the required spring stiffness for offsetting a proportion of the L4/L5 bending moment for each individual in various postures. Study 2 investigated the effectiveness and user acceptability of the PLAD at an automotive manufacturing facility, using operators who performed an assembly process requiring forward bending and static holds. Surface EMG data were collected at six sites on the low back and abdomen, and a tri-axial accelerometer was mounted on each subject’s sternum to measure trunk inclination. A 20% reduction in the L4/L5 bending moment was provided to each wearer using the aforementioned computerized model. The PLAD was able to significantly reduce low back muscular activity, predicted-compression, and ratings of perceived exertion, without significantly changing abdominal activity or trunk inclination. Workers had positive opinions about the device, and 80% said they would wear the device everyday on-line. Additionally, the computerized model developed in Study 1 was effective, as worker low back muscular activity was reduced by approximately 20% when wearing the PLAD. With slight alterations, the PLAD appears to be beneficial in reducing low back forces and discomfort in many tasks that place excessive biomechanical loading on the low back. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2008-08-18 15:55:16.757

No description available.

Canada’s workforce, as well as many other countries, is continuing to age as the baby boomer generation (those born between 1946 and 1964) ages and are remaining in the workforce longer. The number of older workers is estimated to double within the next 10 years (Perry 2010). With increased age, there are a number of factors that could influence worker performance and risk of injury. For example, aging is associated with decreased strength and cardiovascular fitness. However, it is unknown whether a worker’s estimates of how much they can safely lift (based on an approach called psychophysics, which is often used in the design of manual materials handling tasks) is lower for older compared to younger workers. The primary goal of this thesis was to test the hypothesis that psychophysical estimates of maximum acceptable forces would be lower for older workers than younger workers during selected lifting tasks. The secondary goal was to measure a host of variables to provide insights into what factors (e.g. kinematic, strength, cardiovascular) might be influencing potential age-related differences. The experimental testing protocol used a psychophysical approach to identify the maximum acceptable mass of an object during several lifting tasks. Participants comprised a total of 24 female workers (12 older (50+ years old) and 12 younger (20-30 years old)). The primary outcome of interest was the maximum acceptable weight of lift (MAWL) for an 8 hour work day that would allow each participant to ‘work as hard as they can without straining themselves, or becoming unusually tired, weakened, overheated, or out of breath’ (Snook and Ciriello 1991). The participants completed four lifting tasks: floor-to-knuckle height (1 lift/9s and 1 lift/2 min) and knuckle-to-shoulder height (1 lift/2 min and 1 lift/8 hr) by adding or removing lead shot to a lifting box. Tasks were 30 minute in duration; participants could adjust the load mass at any time during the trial. The dependent variables collected were the MAWL (the load mass at the end of the trial), maximum sagittal plane joint angles of the shoulder, hip and knee, overall and body part specific ratings of perceived exertion, and heart rate. Older workers selected MAWL values that were significantly lower (by approximately 24%) than their younger counterparts. These age-related differences were more prevalent for tasks which were constrained by strength (i.e. low frequency) compared to those with large cardiovascular requirements (i.e. high frequency). The only significant difference in the sagittal plane joint flexion angle was for the right hip during the 1 lift/2 min from floor-to-knuckle height lifting task, characterized by 34.4 degree decrease hip angle (more flexed) for the older workers. There were also no significant age-related differences in overall ratings of perceived exertion. The only body part-specific rating of perceived exertion with a significant age-related difference was for the knees, with the younger workers reporting the tasks more taxing on this joint than the older workers. Although there were no age-related differences in absolute heart rate values, the older workers were at a significantly higher percentage of their maximum heart rate. The results of this work suggest there is value in continued research probing whether current ergonomic and work design guidelines need to be updated to accommodate the aging working population. According to the results presented in this study, the current approaches often employed during the design of manual materials handling tasks (i.e. incorporating the loads that 75% of females could perform based on the Snook and Ciriello tables (1991) may not be sufficiently protective for older female workers in the workplace.

Canada’s workforce, as well as many other countries, is continuing to age as the baby boomer generation (those born between 1946 and 1964) ages and are remaining in the workforce longer. The number of older workers is estimated to double within the next 10 years (Perry 2010). With increased age, there are a number of factors that could influence worker performance and risk of injury. For example, aging is associated with decreased strength and cardiovascular fitness. However, it is unknown whether a worker’s estimates of how much they can safely lift (based on an approach called psychophysics, which is often used in the design of manual materials handling tasks) is lower for older compared to younger workers. The primary goal of this thesis was to test the hypothesis that psychophysical estimates of maximum acceptable forces would be lower for older workers than younger workers during selected lifting tasks. The secondary goal was to measure a host of variables to provide insights into what factors (e.g. kinematic, strength, cardiovascular) might be influencing potential age-related differences. The experimental testing protocol used a psychophysical approach to identify the maximum acceptable mass of an object during several lifting tasks. Participants comprised a total of 24 female workers (12 older (50+ years old) and 12 younger (20-30 years old)). The primary outcome of interest was the maximum acceptable weight of lift (MAWL) for an 8 hour work day that would allow each participant to ‘work as hard as they can without straining themselves, or becoming unusually tired, weakened, overheated, or out of breath’ (Snook and Ciriello 1991). The participants completed four lifting tasks: floor-to-knuckle height (1 lift/9s and 1 lift/2 min) and knuckle-to-shoulder height (1 lift/2 min and 1 lift/8 hr) by adding or removing lead shot to a lifting box. Tasks were 30 minute in duration; participants could adjust the load mass at any time during the trial. The dependent variables collected were the MAWL (the load mass at the end of the trial), maximum sagittal plane joint angles of the shoulder, hip and knee, overall and body part specific ratings of perceived exertion, and heart rate. Older workers selected MAWL values that were significantly lower (by approximately 24%) than their younger counterparts. These age-related differences were more prevalent for tasks which were constrained by strength (i.e. low frequency) compared to those with large cardiovascular requirements (i.e. high frequency). The only significant difference in the sagittal plane joint flexion angle was for the right hip during the 1 lift/2 min from floor-to-knuckle height lifting task, characterized by 34.4 degree decrease hip angle (more flexed) for the older workers. There were also no significant age-related differences in overall ratings of perceived exertion. The only body part-specific rating of perceived exertion with a significant age-related difference was for the knees, with the younger workers reporting the tasks more taxing on this joint than the older workers. Although there were no age-related differences in absolute heart rate values, the older workers were at a significantly higher percentage of their maximum heart rate. The results of this work suggest there is value in continued research probing whether current ergonomic and work design guidelines need to be updated to accommodate the aging working population. According to the results presented in this study, the current approaches often employed during the design of manual materials handling tasks (i.e. incorporating the loads that 75% of females could perform based on the Snook and Ciriello tables (1991) may not be sufficiently protective for older female workers in the workplace.

No description available.

In order to investigate the etiology of and evaluate interventions for work-related back injuries, researchers need efficient, accurate occupational exposure assessment methods suitable for large samples. The chapters in this thesis examine critical decisions using electromyography (EMG): How should exposure be measured? For what duration? Who should be measured, and how many times? Low-back EMG, or muscle activity data, was collected during 138 full-shift field measurements over 30 different job titles at 50 different worksites in 5 heavy industries: forestry, transportation, wood products, construction, and warehousing. Observations and self-reports of posture, manual materials handling (MMH), and driving exposures were collected concurrently. 1) Variability of EMG calibration measurements was investigated on right/left sides, multiple trials, 4 positions, and pre/post-shift. Position accounts for the majority of explained variability; there is little to gain by measuring multiple trials or pre- and post-shift, but measuring both sides and multiple positions is worthwhile. 2) Observation and self-report data were easier to collect and cheaper than the EMG direct measure. Costs and successful field performance need to be weighed against the added data detail when making choices about exposure assessment techniques for epidemiological studies. 3) Observed and self-reported exposures were used to predict EMG exposure metrics using mixed multiple linear regression models. Regression models using observed variables predicted 43-50% of the variability in the EMG metrics, while self-reported variables predicted 21%-36%. The observation exposure model provides a low-cost alternative to direct measurement. The self-reported exposure model should be considered with more caution. 4) Full-shift EMG data was resampled for 4, 2, and 1 hour, and for 10 and 2 minute durations to determine the optimal sampling duration. Bias was consistently low, but shorter durations had higher absolute error, percentage error, and limits of agreement. Durations of 4 and 2 hours may be acceptable but those less than 1 hour had large errors. 5) Components of EMG variance were calculated between- and within-subject, and between- industry, company, job, and post hoc grouping. Resolution, contrast, and exposure-response relationship attenuation were calculated for each grouping scheme. The post hoc scheme had the highest contrast and lowest resolution.

In order to investigate the etiology of and evaluate interventions for work-related back injuries, researchers need efficient, accurate occupational exposure assessment methods suitable for large samples. The chapters in this thesis examine critical decisions using electromyography (EMG): How should exposure be measured? For what duration? Who should be measured, and how many times? Low-back EMG, or muscle activity data, was collected during 138 full-shift field measurements over 30 different job titles at 50 different worksites in 5 heavy industries: forestry, transportation, wood products, construction, and warehousing. Observations and self-reports of posture, manual materials handling (MMH), and driving exposures were collected concurrently. 1) Variability of EMG calibration measurements was investigated on right/left sides, multiple trials, 4 positions, and pre/post-shift. Position accounts for the majority of explained variability; there is little to gain by measuring multiple trials or pre- and post-shift, but measuring both sides and multiple positions is worthwhile. 2) Observation and self-report data were easier to collect and cheaper than the EMG direct measure. Costs and successful field performance need to be weighed against the added data detail when making choices about exposure assessment techniques for epidemiological studies. 3) Observed and self-reported exposures were used to predict EMG exposure metrics using mixed multiple linear regression models. Regression models using observed variables predicted 43-50% of the variability in the EMG metrics, while self-reported variables predicted 21%-36%. The observation exposure model provides a low-cost alternative to direct measurement. The self-reported exposure model should be considered with more caution. 4) Full-shift EMG data was resampled for 4, 2, and 1 hour, and for 10 and 2 minute durations to determine the optimal sampling duration. Bias was consistently low, but shorter durations had higher absolute error, percentage error, and limits of agreement. Durations of 4 and 2 hours may be acceptable but those less than 1 hour had large errors. 5) Components of EMG variance were calculated between- and within-subject, and between- industry, company, job, and post hoc grouping. Resolution, contrast, and exposure-response relationship attenuation were calculated for each grouping scheme. The post hoc scheme had the highest contrast and lowest resolution.

In order to investigate the etiology of and evaluate interventions for work-related back injuries, researchers need efficient, accurate occupational exposure assessment methods suitable for large samples. The chapters in this thesis examine critical decisions using electromyography (EMG): How should exposure be measured? For what duration? Who should be measured, and how many times? Low-back EMG, or muscle activity data, was collected during 138 full-shift field measurements over 30 different job titles at 50 different worksites in 5 heavy industries: forestry, transportation, wood products, construction, and warehousing. Observations and self-reports of posture, manual materials handling (MMH), and driving exposures were collected concurrently. 1) Variability of EMG calibration measurements was investigated on right/left sides, multiple trials, 4 positions, and pre/post-shift. Position accounts for the majority of explained variability; there is little to gain by measuring multiple trials or pre- and post-shift, but measuring both sides and multiple positions is worthwhile. 2) Observation and self-report data were easier to collect and cheaper than the EMG direct measure. Costs and successful field performance need to be weighed against the added data detail when making choices about exposure assessment techniques for epidemiological studies. 3) Observed and self-reported exposures were used to predict EMG exposure metrics using mixed multiple linear regression models. Regression models using observed variables predicted 43-50% of the variability in the EMG metrics, while self-reported variables predicted 21%-36%. The observation exposure model provides a low-cost alternative to direct measurement. The self-reported exposure model should be considered with more caution. 4) Full-shift EMG data was resampled for 4, 2, and 1 hour, and for 10 and 2 minute durations to determine the optimal sampling duration. Bias was consistently low, but shorter durations had higher absolute error, percentage error, and limits of agreement. Durations of 4 and 2 hours may be acceptable but those less than 1 hour had large errors. 5) Components of EMG variance were calculated between- and within-subject, and between- industry, company, job, and post hoc grouping. Resolution, contrast, and exposure-response relationship attenuation were calculated for each grouping scheme. The post hoc scheme had the highest contrast and lowest resolution. / Medicine, Faculty of / Population and Public Health (SPPH), School of / Graduate

Made available in DSpace on 2016-06-02T20:19:19Z (GMT). No. of bitstreams: 1 4746.pdf: 1426086 bytes, checksum: f41b8c37c91b06ab62579658c926ad62 (MD5) Previous issue date: 2012-11-20 / Universidade Federal de Sao Carlos / With the rapid development of civil aviation in Brazil there was a large number of subjects involved in the aircraft maintenance work. Much of workers develop tasks involving manual material handling (MMH), which already have evidenced musculoskeletal risks. However, workers from the aircraft maintenance industry suffer huge pressure due the safety issues and the quality of the work that is performed. There were no studies in the literature that addressed the risk factors present in this sector. Thus, the aim of Study 1 was to evaluate the psychosocial indicators, as well as reports of musculoskeletal symptoms and disorders among workers iof the aircraft maintenance industry. One hundred and one employees were assessed using the Nordic Musculoskeletal Questionnaire, a standardized physical examination, the Job Content Questionnaire and the Utrecht Work Engagement Scale. The results indicate that the workers are exposed to good psychosocial conditions, which have neither prevented the emergence of musculoskeletal disorders, nor the self reported pain and functional disability, particularly associated with the lower back. As the MMH was the main activity performed by the aircraft maintenance workers assessed, musculoskeletal disorders seem to be associated with the biomechanical characteristics of this activity. Despite the risks already identified, the literature suggests some strategies for reducing the physical load imposed to the musculoskeletal system during MMH. These strategies such as the implementation of handles on boxes, ensuring better coupling object/hands during handling. However, the recommendations of adaptations in boxes are not conclusive regarding handle placement, and their impact on workers' musculoskeletal conditions. Thus, the Study 2 was conducted based on a systematic literature review. The aim was to synthesize evidence regarding the effect of adjustment on boxes, aiming at reduction of musculoskeletal load. A survey was conducted in the following databases: Embase, Pubmed / Medline, Web of Science, and Lilacs Bireme CINAHAL, Sportdiscuss, Cochrane. Two reviewers independently selected the relevant studies, and any disagreements were solved by consensus. Cross-sectional studies were included. The scale proposed by Ariens (2000) was used to assess the quality of the studies included in this review. The electronic search yielded a total of 1170 references published in English. At the end of the selection process, and after manual search of references, the selection included 15 cross-sectional studies. Due to do the great methodological variability, regarding both methods and the proposed adaptations (size and mass of boxes), associated with the low quality of the studies prevented the synthesis of evidence. There is a need of using objective and subjective methods to evaluate standardized boxes with handles, which can also be applied to the assessment of other ergonomic interventions. Furthermore, the handles should be investigated using various positions and inclinations, and the MMH has to be carried out to different heights, in order to provide more conclusive evidence to support the implementation of those adaptations in the occupational practice. Experienced subjects have also to be considered in future studies. / Com o desenvolvimento acelerado da aviação civil no Brasil observou-se um elevado número de sujeitos envolvidos com o trabalho de manutenção de aeronaves. Grande parte dos trabalhadores desenvolvem tarefas que envolvem a realização do manuseio de cargas, o qual já tem grandes evidências de riscos musculoesqueléticos. No entanto, o setor de manutenção de aeronaves sofre grandes pressões com a segurança e com a qualidade do trabalho realizado. Não foram encontrados na literatura estudos que abordassem os fatores de risco presentes neste setor. Dessa forma, o Estudo 1 teve como objetivo avaliar os indicadores psicossociais, assim como os relatos de sintomas musculoesqueléticos entre trabalhadores do setor de manutenção de aeronaves. Cento e um funcionários foram avaliados por meio do Questionário Nórdico de Sintomas Osteomusculares, por uma avaliação física padronizada e pelas Escala de Estresse e Trabalho e a Escala de Bem Estar e Trabalho. Os resultados indicam que trabalhadores da indústria de manutenção de aeronaves envolvidos com tarefas de manuseio de materiais são expostos a boas condições psicossociais, o que não impediu o surgimento de distúrbios musculoesqueléticos, nem o alto índice de relato de dor e incapacidade funcional, particularmente associado com a parte inferior da coluna. Como o manuseio de materiais foi a principal atividade realizada no setor de manutenção de aeronaves avaliado, os distúrbios musculoesqueléticos encontrados foram associados às características biomecânicas desta atividade. Apesar dos riscos já identificados, a literatura aponta algumas estratégias para redução da carga física imposta ao sistema musculoesquelético durante o manuseio de cargas. Tratam-se de estratégias nos instrumentos de trabalho, como a implementação de pegas em caixas, garantindo melhor acoplamento objeto/mãos durante o manuseio. No entanto, as adaptações em caixas não são conclusivas em relação às recomendações de posicionamento e sua repercussão nas condições musculoesqueléticas dos trabalhadores. Desta forma, foi realizado o Estudo 2 desta dissertação a partir de uma revisão sistemática da literatura. O objetivo foi sintetizar evidências em relação ao efeito da adaptação de caixas na redução da carga musculoesquelética. Foi realizada pesquisa nas seguintes bases de dados: dados Embase, Pubmed/Medline, Web of Science, Bireme e Lilacs CINAHAL, Sportdiscuss, Cochrane. Dois revisores independentes selecionaram os estudos pertinentes, e as eventuais discordâncias foram solucionadas por consenso. Foram incluídos estudos tranversais. A escala proposta por Ariens (2000) foi utilizada para avaliação da qualidade dos estudos incluídos nesta revisão. A busca eletrônica resultou em um total de 1170 referências publicadas em inglês. Ao final do processo de seleção e da busca manual das referências dos artigos inicialmente incluídos na revisão, totalizou-se a seleção de 15 estudos transversais. A grande variabilidade metodológica, tanto em termos de avaliação como em relação às formas de adaptação de pegas propostas, tamanho e massa das caixas, associadas à baixa qualidade dos estudos incluídos, inviabilizou o agrupamento dos estudos para síntese de evidência. Observa-se a necessidade da utilização conjunta de metodologias objetivas e subjetivas padronizadas na avaliação de caixas adaptadas com pegas, o que pode ser estendido para outros tipos de intervenções ergonômicas. Além disso, as caixas adaptadas precisam ser investigadas a partir de diferentes posicionamentos e inclinações das pegas, a serem manuseadas em diferentes alturas, para fornecer evidências mais definitivas para a implementação na prática ocupacional. A questão da experiência dos sujeitos avaliados também deve ser considerada em estudos futuros.