Lifting is one of the major causes of back injury in the workplace. Often, workers are told to ask for the help of another worker when the load is too great to be lifted alone, yet the effects of these team lifts have not been researched until recently. This experiment investigated some of the variables which may affect the results of team lifting tasks. The psychophysical methodology has been used for almost 30 years in trying to determine the maximum acceptable weight of lift for industrial workers. Though two previous studies of team lifting used the psychophysical approach, no effort was made to identify and control variables which may affect team tasks. This experiment manipulated two variables, box type (double or single) and isolation condition (curtains open or closed) to see whether these would produce the psychosocial effects of social loafing and social facilitation. Three male and three female two-person teams performed team lifts, using psychophysical methodology, under all four conditions. The only significant effect found was for gender. Female teams lifted 58.8% of the mass the male teams lifted. Male teams lifted 92.5% and female teams 87.8% of the sum of their individual lifts. This is in close agreement with other studies of team lifting. A regression model was developed in order to predict the amount of weight a team can lift, with an R₂ of 0.962. The external validity of the task conditions was also investigated. / Master of Science

The occupation of sheep-shearing is classified as heavy to very-heavy physical work requiring a high level of energy expenditure while performing a repetitive task in a predominantly sustained trunk flexion posture. The task is further complicated by unpredictable animal behaviour. Shearing is considered to carry a high risk of injury particularly to the lumbar spine and epidemiological studies have demonstrated that the prevalence of low back pain (LBP) in shearers is high relative to other occupations. The emergence of a commercial shearing-aid (Warrie Back-Aid TM) that is purported to decrease loading on the spine, reduce injury rate and alleviate symptoms of spinal origin has been welcomed by many sectors of the wool-harvesting industry. However, the precise biomechanical influence of the Warrie Back-Aid TM (WBA) on the sheep-shearing task has not been quantified. The purpose of this study was to investigate the effect of the WBA on three-dimensional kinematics and electromyography of the trunk for 12 experienced shearers during the occupational task of sheep-shearing. Sheep-shearing is a highly patterned process comprised of specific interlinked phases. Nine distinct phases of the shearing-task where the harness was worn during the removal of the sheep�s fleece were investigated. The study used an opto-electronic motion analysis system and rigid body dynamic modelling. The shearer�s trunk and pelvis were considered as a series of three coupled rigid segments; pelvis, lumbar, and thorax with four passive retro-reflective markers defining each segment. The kinematic variables of angular displacement, velocity and acceleration at the thoraco-lumbar and lumbo-pelvic joint centres were calculated for each shearer while shearing with and without the WBA. An eight channel sEMG telemetry system was used to simultaneous record activity in four pairs of trunk muscles. Temporal analysis of the sEMG signal gave information on the duration and relative intensity of trunk muscle activity. The results demonstrated that the task of sheep-shearing required endurance-based muscle activity and the adoption of quasi-static posturing combined with complex asymmetrical trunk motion for extensive periods of the task time. There was considerable variability in the trunk motion of individual shearers despite the pattern-taught and repeatable nature of the shearing task. The introduction of the WBA had no effect on the time taken to shear or trunk kinematics however it resulted in reductions in muscular activity of the trunk extensors. When the complete shearing task was analysed there was a statistically significant reduction in mean intensity of muscle activity for the left multifidus (p = 0.010), right multifidus (p = 0.001), right iliocostalis (p = 0.004) and right longissimus (p = 0.002) when the WBA was used. A reduction in muscular activity of the trunk extensors during the sheep-shearing task may result in a decrease in spinal loading, energy expenditure and muscular fatigue. The clinical recommendation based on the biomechanical results of this and other studies is that the WBA should be incorporated into the practice of sheep-shearing to assist in the reduction of inherent risks associated with the shearing task. Prospective studies into the effect of the harness on LBP are required to endorse this recommendation.

The occupation of sheep-shearing is classified as heavy to very-heavy physical work requiring a high level of energy expenditure while performing a repetitive task in a predominantly sustained trunk flexion posture. The task is further complicated by unpredictable animal behaviour. Shearing is considered to carry a high risk of injury particularly to the lumbar spine and epidemiological studies have demonstrated that the prevalence of low back pain (LBP) in shearers is high relative to other occupations. The emergence of a commercial shearing-aid (Warrie Back-Aid TM) that is purported to decrease loading on the spine, reduce injury rate and alleviate symptoms of spinal origin has been welcomed by many sectors of the wool-harvesting industry. However, the precise biomechanical influence of the Warrie Back-Aid TM (WBA) on the sheep-shearing task has not been quantified. The purpose of this study was to investigate the effect of the WBA on three-dimensional kinematics and electromyography of the trunk for 12 experienced shearers during the occupational task of sheep-shearing. Sheep-shearing is a highly patterned process comprised of specific interlinked phases. Nine distinct phases of the shearing-task where the harness was worn during the removal of the sheep�s fleece were investigated. The study used an opto-electronic motion analysis system and rigid body dynamic modelling. The shearer�s trunk and pelvis were considered as a series of three coupled rigid segments; pelvis, lumbar, and thorax with four passive retro-reflective markers defining each segment. The kinematic variables of angular displacement, velocity and acceleration at the thoraco-lumbar and lumbo-pelvic joint centres were calculated for each shearer while shearing with and without the WBA. An eight channel sEMG telemetry system was used to simultaneous record activity in four pairs of trunk muscles. Temporal analysis of the sEMG signal gave information on the duration and relative intensity of trunk muscle activity. The results demonstrated that the task of sheep-shearing required endurance-based muscle activity and the adoption of quasi-static posturing combined with complex asymmetrical trunk motion for extensive periods of the task time. There was considerable variability in the trunk motion of individual shearers despite the pattern-taught and repeatable nature of the shearing task. The introduction of the WBA had no effect on the time taken to shear or trunk kinematics however it resulted in reductions in muscular activity of the trunk extensors. When the complete shearing task was analysed there was a statistically significant reduction in mean intensity of muscle activity for the left multifidus (p = 0.010), right multifidus (p = 0.001), right iliocostalis (p = 0.004) and right longissimus (p = 0.002) when the WBA was used. A reduction in muscular activity of the trunk extensors during the sheep-shearing task may result in a decrease in spinal loading, energy expenditure and muscular fatigue. The clinical recommendation based on the biomechanical results of this and other studies is that the WBA should be incorporated into the practice of sheep-shearing to assist in the reduction of inherent risks associated with the shearing task. Prospective studies into the effect of the harness on LBP are required to endorse this recommendation.

by Wan Yu Kwan. / Thesis submitted in: December 1999. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 112-125). / Abstracts in English and Chinese. / Acknowledgement --- p.2 / Abstract --- p.3 / Table of Contents --- p.5 / Chapter Chapter 1 - --- Introduction --- p.7 / Chapter 1.1 --- Contribution of lifting techniques on risk assessment and training on manual materials handling --- p.7 / Chapter 1.2 --- Objectives --- p.12 / Chapter 1.3 --- Hypotheses --- p.12 / Chapter 1.4 --- Significance of Study --- p.13 / Chapter Chapter 2 - --- Literature Review --- p.14 / Chapter 2.1 --- Societal concerns on employee compensation --- p.14 / Chapter 2.2 --- Etiology of low back injury --- p.15 / Chapter 2.2.1 --- Compression forces on vertebral joints --- p.16 / Chapter 2.2.2 --- Shear forces on vertebral joints --- p.17 / Chapter 2.3 --- Lifting techniques --- p.18 / Chapter 2.3.1 --- Effect of lifting techniques on curvature of the spine --- p.22 / Chapter 2.3.2 --- Importance of leg muscles in manual lifting --- p.22 / Chapter 2.4 --- Prediction of low back injury in manual lifting --- p.24 / Chapter 2.4.1 --- Compression forces and moments --- p.26 / Chapter 2.4.2 --- Balance control --- p.29 / Chapter 2.4.3 --- Application of Surface electromyography in ergonomics --- p.31 / Chapter Chapter 3 - --- Method --- p.34 / Chapter 3.1 --- Subject recruitment --- p.34 / Chapter 3.2 --- Equipment --- p.35 / Chapter 3.2.1 --- Force platform --- p.35 / Chapter 3.2.2 --- Motion analysis system --- p.37 / Chapter 3.2.3 --- Surface electromyography --- p.38 / Chapter 3.3 --- Maximum voluntary contraction test --- p.40 / Chapter 3.3.1 --- MVC of vastus medialis --- p.41 / Chapter 3.3.2 --- MVC of medial gastrocnemius --- p.42 / Chapter 3.3.3 --- MVC of erector spinae --- p.43 / Chapter 3.4 --- Lifting techniques --- p.44 / Chapter 3.5 --- Experimental procedures --- p.48 / Chapter 3.6 --- Statistical analysis --- p.53 / Chapter Chapter 4 - --- Results and Dicussion --- p.54 / Chapter 4.1 --- No. of cases in the study --- p.54 / Chapter 4.2 --- Phases of lifting --- p.55 / Chapter 4.3 --- Process time --- p.56 / Chapter 4.4 --- Trunk inclination angles --- p.62 / Chapter 4.5 --- Hip joint angles --- p.67 / Chapter 4.6 --- Knee joint angles --- p.73 / Chapter 4.7 --- Center of mass of box --- p.79 / Chapter 4.8 --- Muscle activities --- p.84 / Chapter Chapter 5 - --- Conclusion --- p.109 / Chapter Chapter 6 - --- References --- p.112

No description available.

One hundred persons applying for services with the Texas Rehabilitation Commission with reported disabilities of alcohol/substance abuse or back injury/pain were selected for study. Subjects were assigned to two groups (alcohol or back) according to their reported disability. They were tested within one week of application and after 60 days were checked to see what rehabilitation status they were in to determine success or failure. Alcohol clients were administered the Health Attribution Test (HAT), 16PF, and an Alcohol Imagery questionnaire developed for this study. Back clients were administered the HAT, 16PF, and Pain Drawings. Statistical procedures including Pearson correlation, stepwise discriminant analysis, and discriminant analysis were performed. The HAT Internal Factor showed a significant relationship to rehabilitation success or failure and the 16PF motivation indices approached significance. The discriminant analysis demonstrated that success or failure could be predicted at a significant level using these measures. Issues of practicality in using these instruments (particularly imagery measures) in a rehabilitation counseling practice were noted.

"Back injuries have consistently been the most common types of injuries suffered by people at work. They have been a significant worker injury problem in most, if not all, industrialised countries for many years and manual handling has long been established as a significant task related back injury causal factor.[...] This research project established that the manufacturers of the jet airlines used by the airlines in this study had not previously been acquainted with the issue of baggage handler back injuries.[...] This study also canvassed the opinion of airline safety professionals and airline baggage handlers concerning baggage handling tasks and working environment related causal factors. [...] A major focus of this research project was also to measure the effect of ACE and Sliding Carpet, two commercially available retro-fit baggage systems, on the risk of back injuries to baggage handlers stacking baggage within Boeing B737 narrow-body aircraft." / Doctor of Philosophy

"Back injuries have consistently been the most common types of injuries suffered by people at work. They have been a significant worker injury problem in most, if not all, industrialised countries for many years and manual handling has long been established as a significant task related back injury causal factor.[...] This research project established that the manufacturers of the jet airlines used by the airlines in this study had not previously been acquainted with the issue of baggage handler back injuries.[...] This study also canvassed the opinion of airline safety professionals and airline baggage handlers concerning baggage handling tasks and working environment related causal factors. [...] A major focus of this research project was also to measure the effect of ACE and Sliding Carpet, two commercially available retro-fit baggage systems, on the risk of back injuries to baggage handlers stacking baggage within Boeing B737 narrow-body aircraft." / Doctor of Philosophy