Occupational Ergonomics - Volume 8, issue 1

Authors: Christie, Candice Jo-Anne

Article Type: Research Article

Abstract: The objective of this study was to compare the energy demands of manual harvesting tasks with the associated energy intake of the workers'. Fifty eight workers (29 Chainsaw Operators and 29 Stackers) were assessed in South Africa prior to, and during a 'normal' working shift. Habitual dietary analyses showed that the workers were eating less than 56% of the recommended daily allowance and were thus arriving at work with reduced energy stores. Heart rate responses were measured continuously during work and energy expenditure was predicted from the heart rate/oxygen uptake relationship obtained at a post-work progressive step up test completed …by each worker. The data indicated that the tasks placed 'moderate-to-heavy' demands on the workers resulting in a significant imbalance between the energy demands of the tasks and the associated energy intake of the workers. Energy deficits were in excess of 8 000 kJ and workers lost, on average, 2.8% body mass during work while felling and cross-cutting, and 3.6% during stacking. Show more

Keywords: Chainsaw Operators, Stackers, energy intake, energy expenditure, dehydration

DOI: 10.3233/OER-2008-8101

Citation: Occupational Ergonomics, vol. 8, no. 1, pp. 1-10, 2008

Authors: Andrews, David M. | Arnold, Tara A. | Weir, Patricia L. | van Wyk, Paula M. | Callaghan, Jack P.

Article Type: Research Article

Abstract: The trunk posture misclassification errors made by novice and experienced operators were quantified as a function of the angular distance from posture bin boundaries, similar to those used in observation-based posture assessment tools such as 3DMatch. The effect that these misclassification errors had on cumulative and peak low back loads was also determined in three simulated lifting scenarios. Ninety subjects in 3 experience groups were randomly presented with images of known trunk angle via a monitor. Subjects were instructed to make quick and accurate bin selections using standardized pictures included below the images on the monitor. Mean % bin misclassification …errors were approximately 32% and 22% for the flexion/extension and lateral bend views, respectively. More bin classification errors were made the closer a viewed image was to a posture bin boundary, regardless of expertise level, and the number of errors made decreased as operator experience increased. Approximately 99% of bin selections were made either in the correct bin or in the bins immediately adjacent to the correct bin in both views. Misclassification errors made in the 3 simulated lifting scenarios induced errors in peak and cumulative loads in 66% of the cases assessed, with an average absolute difference of 13.5% across all load variables. Future work is aimed at determining the effect of training and bin size on the error misclassification rate for all body segments and views. Show more

Keywords: Trunk posture assessment, posture bin boundaries, misclassification errors, low back loads, cumulative loading

DOI: 10.3233/OER-2008-8102

Citation: Occupational Ergonomics, vol. 8, no. 1, pp. 11-25, 2008

Authors: Hess, Jennifer A. | Kincl, Laurel D. | Albers, Jim T. | High, Robin R.

Article Type: Research Article

Abstract: Carpenters frequently work in awkward and stooped postures. Autofeed extension screw guns (ESGs) allow certain tasks to be performed upright. This study evaluated low back and wrist motion in fifteen carpenters using a traditional screw gun (TSG) and ESG during floor level work. ESG use required a greater percentage of time in awkward wrist postures with higher velocities and accelerations, yet neither tool placed workers at risk for wrist injury. The ESG resulted in significantly less low back flexion, left-sided bending and twisting, velocity and acceleration. The probability of low back disorder group membership risk was 53% with TSG use …and 47% with ESG use. Carpenters liked using ESGs and reported less exertion when using them. The ESG's autofeed feature enhanced productivity. Training may be important to further reduce back flexion and improve tool maintenance, and design changes would improve ESGs overall. Show more

Keywords: Ergonomics, low back disorders, wrist, construction, biomechanics

DOI: 10.3233/OER-2008-8103

Citation: Occupational Ergonomics, vol. 8, no. 1, pp. 27-40, 2008

Authors: Kothiyal, Kamal | Li, Frank | Yiu, Ida

Article Type: Research Article

Abstract: This paper presents the results of a comparative study of load sharing among back and leg muscles during squat and half-kneeling lifts. 19 young and healthy subjects with no history of low back pain or other musculoskeletal disorders participated in the study. Muscle activity was measured using electromyography (EMG) technique. Surface EMG electrodes were placed bilaterally at the erector spinae, quadriceps and hamstring muscles. Muscle activities were determined at different force levels representing 40, 60 and 80 percent of maximal voluntary contraction (MVC). The results showed increase in normalised mean RMS (root mean squared) values of EMG of for all …the muscles with increasing force levels in both squat and half kneeling lifts. Contralateral and ipsilateral ratio parameters were used to determine the degree of load sharing among the muscles in both lifting postures. Statistical analysis of the mean RMS values and the contralateral and ipsilateral ratio parameters revealed no significant differences between squat and half kneeling lifts. The paper discusses the implications of the results for preventing injuries during manual handling and provides suggestions for future research. Show more

Keywords: Electromyography, lifting postures, manual handling, load sharing, non-standard postures

DOI: 10.3233/OER-2008-8104

Citation: Occupational Ergonomics, vol. 8, no. 1, pp. 41-52, 2008

Authors: Grieve, Jason R. | Dickerson, Clark R.

Article Type: Research Article

Abstract: Overhead work is one determinant of the genesis and propagation of shoulder occupational musculoskeletal disorders and muscle fatigue. This is a result of a combination of organizational, biomechanical and physiological factors. In this paper, evidence for identification of the mechanisms of fatigue and injury associated with overhead work is presented in the context of ergonomic design guidance. Secondarily, although significant research efforts have analyzed and interpreted overhead work, there are limited resources available to ergonomists in which theoretical and practical concerns are combined in a single source. This review paper aims to address this deficiency by reporting on the mechanisms …of exposure in overhead work and their associated negative health and performance outcomes. Show more

Keywords: Overhead work, shoulder biomechanics, fatigue, work design

DOI: 10.3233/OER-2008-8105

Citation: Occupational Ergonomics, vol. 8, no. 1, pp. 53-66, 2008