Occupational Ergonomics - Volume 3, issue 2

Authors: Bhattacharya, Amit | Succop, Paul | Kincl, Laurel | Lu, Ming Lun | Bagchee, Angshuman

Article Type: Research Article

Abstract: The purpose of this study was to subjectively and objectively evaluate the postural stability of forty industrial workers while performing simulated industrial tasks on inclined and elevated surfaces under various combinations of environmental lighting and noise distraction conditions. The results suggest the following ordering for the effects of risk factors on objective measure of postural balance: (1) environmental lighting, (2) elevation of standing surface, (3) gender, (4) inclination of standing surface, (5) age. The task performed would be ranked highest had the data been analyzed across the three tasks. The postural sway length significantly increased with increasing elevations and inclination …angles for the stationary and bending tasks implying body's perceived risk of fall deployed increase in postural muscle contraction. This compensatory mechanism indicated by increased sway length actually did reduce postural sway amplitudes with increasing elevation but for increasing inclination the postural sway amplitudes increased. While the objective measure of postural sway increased with the increasing combination of elevation and inclination, the subjective measure of stability did not show a significant two way interaction, implying that the participants were not able to perceive the combined risk to postural imbalance, causing potential inability to deploy appropriate postural muscle corrective actions. Show more

Keywords: elevation, inclination, postural stability, perceived sense of slip/fall, occupational safety

DOI: 10.3233/OER-2003-3201

Citation: Occupational Ergonomics, vol. 3, no. 2, pp. 83-97, 2003

Authors: Davis, Kermit G. | Splittstoesser, Riley E. | Marras, William S.

Article Type: Research Article

Abstract: Although there have been numerous studies evaluating the difference between stooped and squat lifting styles, there remains a lack of understanding of whole body kinematics during unrestricted lifting. The current study evaluated nine males and nine females while lifting two box weights (9.1 kg, 18.2 kg) from five origins below the waist (0, 19, 38, 57, and 76 cm above the floor) and from three task asymmetries (sagittally symmetric, 45° clockwise, 45° counter-clockwise). While the lifting style was significantly influenced by the height of lift origin and to a lesser extent gender, box weight, and task asymmetry, none of the …conditions resulted in pure squat or stoop lifting style. However, for lifts above knee height, the lifting style resembled more of a stoop lift while lifts originating below knee height were more of a squat lift. As the origin moved closer to the floor, participants relied more on their hips to accomplish the sagittal flexion but overall adopted a more coordinated whole-body lifting style. All together, as more sagittal flexion is required, more joints are relied upon in a more coordinated effort. The current study indicates that caution needs to be exercised when applying results of pure squat or pure stoop lifting studies to free-style (realistic) lifting. Show more

Keywords: lifting style, biomechanics, manual material handling, coordination, low back

DOI: 10.3233/OER-2003-3202

Citation: Occupational Ergonomics, vol. 3, no. 2, pp. 99-108, 2003

Authors: Karwowski, Waldemar | Gielo-Perczak, Krystyna | Moxley, David | Rodrick, David

Article Type: Research Article

Abstract: The objective of this study was to analyze human perception of load heaviness in manual material handling tasks under varying task parameters taking into consideration participants' physical ability and willingness to lift loads. These conditions were: 1) box color, 2) instruction set, and 3) space confinement. The effect of each parameter on the maximum acceptable weight that people are willing to lift was investigated. This study showed that the box color significantly affects a participant's perception of weight. The average maximum acceptable weight participants were willing to lift was higher for the black boxes than for the white boxes in …both open and constrained spaces. When using the white boxes, the maximum acceptable weight participants were willing to lift was smaller in the confined space than in the open space. This study introduces an ecological approach to manual handling tasks and proposes the paradigm of maximum acceptable weight of load (MAWL) to the maximum loads that people perceive they are able and willing to lift (MLWL). Show more

Keywords: task parameters, physical ability, lifting willingness, ecological approach

DOI: 10.3233/OER-2003-3203

Citation: Occupational Ergonomics, vol. 3, no. 2, pp. 109-119, 2003

Authors: Chervak, Steven G. | Drury, Colin G.

Article Type: Research Article

Abstract: Written documentation has been implemented in aviation maintenance errors so that documentation becomes an important safety issue. A restricted technical language for job instruction, Simplified English was tested to determine whether or not it reduced error rate in a maintenance task. Experienced and inexperienced participants performed on easy and a difficult maintenance task on a small internal combustion engine using three languages of job instruction: original, Simplified English and a hybrid. Task errors were reduced with Simplified English but increased with the hybrid version. While the easy task and the experienced participants made fewer errors, neither participant expertise nor task …difficulty interacted with instruction language. Hence, Simplified English can be recommended, but hybrid instructions should be avoided. Show more

Keywords: job instruction, maintenance task, task error, Simplified English

DOI: 10.3233/OER-2003-3204

Citation: Occupational Ergonomics, vol. 3, no. 2, pp. 121-131, 2003

Authors: Voorbij, Liek | Snijders, Chris J.

Article Type: Research Article

Abstract: The maximal peak and build-up forces at elbow flexion of 140° were measured without a wrist cuff. Peak force was found to be significantly higher than build-up force. The results established that peak force is more easiliy reproducible than build-up force. For women, the force studied did not decrease with age. The results of this investigation are believed to be useful for product designers in adjusting the product characteristics to deal with the loads exerted by users in peak force exertion.

Keywords: elbow flexion forces, peak forces, build-up forces, isometric force

DOI: 10.3233/OER-2003-3205

Citation: Occupational Ergonomics, vol. 3, no. 2, pp. 133-139, 2003