Occupational Ergonomics - Volume 4, issue 1

Authors: Morose, Tanya | Greig, Michael | Wells, Richard

Article Type: Research Article

Abstract: This study was undertaken to evaluate the utility of using a force and moment wrench to describe the demand on the distal arm tissues and perceived exertion during static gripping tasks. Five right hand dominant university students, who were free of hand or wrist disorders, completed a total of 87 maximum and submaximum gripping tasks. All trials were completed while standing, with the arm adducted and elbow flexed to ninety degrees. The wrist posture was near neutral in all axes during the exertions. Activation levels for muscles of the forearm and hand and rating of perceived exertion were collected. Participants …handled objects using 3 grips (cylindrical grip, lateral pinch and pulp pinch) in 8 different ways. The equivalent force and moment wrench for the tasks were also exerted on a modified pinch/grip dynamometer, affixed to a six degree of freedom force cube. This instrumentation allowed the simultaneous collection of the 3 forces, 3 moments and the pinch/grip force about the grip centre. It was expected that the demands of a task and the instrumented task wrench reproduction would be the same, and therefore the slope of the linear regression for the EMG and RPE scatterplots would be equal to one. The RPE slopes ranged from 0.99 (lateral pinch) to 1.11 (cylindrical grip), with R2 greater than 0.89 for all grips. The mean slope for EMG of all muscles ranged from 0.89 (lateral pinch) to 1.38 (pulp pinch), with mean R2 of 0.61 to 0.68. The force and moment wrench system for the categorization of prehension appears to capture the demands on the distal arm tissues and perceived exertion during standardized laboratory holding tasks. Show more

Keywords: hand grip, hand force, wrench, EMG

DOI: 10.3233/OER-2004-4101

Citation: Occupational Ergonomics, vol. 4, no. 1, pp. 1-10, 2004

Authors: Cham, Rakié | Redfern, Mark S.

Article Type: Research Article

Abstract: The complex human processes involved in balance maintenance and fall prevention during normal locomotion are further complicated by load carrying and/or the presence of slippery floors. The goal of this study was to investigate the effect of carrying loads (2-handed method) on gait biomechanics relevant to slips/falls. Participants walked down surfaces of varying inclinations (0°, 5° and 10°), while ground reaction forces and body/foot motion were recorded. Three load conditions (no load, 2.3 and 6.8 kg) were included. Load carrying was associated with increases in the peak normal ground reaction force and in the rate of the normal loading phase …on the leading foot. Shear ground reaction forces were not affected by load carrying. Changes in the ground reaction forces recorded during load carrying led to reduced required coefficient of friction (RCOF) values, a variable used to rate slip potential. This RCOF reduction is partly due to postural adaptations such as increased knee and hip flexion adopted during load carrying. Furthermore, load carrying was accompanied by slower heel contact heel velocity in the direction of motion. Finally, moments generated at the hip and knee joints were significantly biased towards the extensor and flexor direction, respectively. Show more

Keywords: load carrying, slip, slip potential, gait, gait biomechanics

DOI: 10.3233/OER-2004-4102

Citation: Occupational Ergonomics, vol. 4, no. 1, pp. 11-26, 2004

Authors: Eger, Tammy R. | Stevenson, Joan M.

Article Type: Research Article

Abstract: Load transfer force to the hands was investigated to provide an accurate estimate of load transfer during sagittal lifting tasks for application in an industrial setting. The effects of gender, load mass, lift style, load transfer duration and participant strength were examined as possible variables to improve the estimation of load transfer force. Ten healthy men and eleven healthy women completed a total of 25 box lifts using a freestyle technique. Kinematic data were collected using the OPTOTRAK™ and a portable video camera. Measured load transfer force (MLTF) was determined as the total load weight minus measured values from a …force plate. Five methods of estimating load transfer to the hands were calculated and compared with MLTF. The enhanced load transfer force method (ELTF) of estimating load transfer to the hands was superior to all other estimation methods. Show more

Keywords: load transfer, hand forces, lifting, lifting style, lumbar moments

DOI: 10.3233/OER-2004-4103

Citation: Occupational Ergonomics, vol. 4, no. 1, pp. 27-39, 2004

Authors: Karwowski, Waldemar | Rodrick, David | Boratyn, Grzegorz

Article Type: Research Article

Abstract: The main objective of this study was to perform experimental evaluation of the human body-pad interface pressure distribution changes when using five different clinical support surfaces (pads). The studied pads included the support surfaces for: head, heel, hip, lower back, and multipurpose pad for relevant body segments. For each pad, experimental data from 44 independent trials were obtained using 22 participants (12 male and 10 female) who voluntarily participated in the study. To measure the human body interface pressure, an Advanced ClinSeat pressure measurement system was utilized. For pads of the head, heel, lower back, and shoulder, the participants were …positioned on their back, while for the hip pad, the participants were placed on their side. The results showed that in all cases the recorded pressures were significantly lower when the participants used the comfort pads compared to the no-pad condition. Specific recommendations for improvements in the current pad design were provided. Show more

Keywords: comfort pads, pressure distribution, body comfort

DOI: 10.3233/OER-2004-4104

Citation: Occupational Ergonomics, vol. 4, no. 1, pp. 41-50, 2004

Authors: Dalton, Jean | Drury, Colin G.

Article Type: Research Article

Abstract: Three studies were performed to better understand the complex task of sheet steel inspection for multiple surface defects. Their aim was to combine techniques from off-line performance measurement studies with interviews and questionnaires coming from a more holistic tradition of inspection. In this way, more detailed insights were obtained from three studies of nine highly-trained and experienced steel inspectors. The performance study was designed to compare lighting conditions using a visual search task. It did not find lighting differences, but did find other task differences and the typical large individual differences. These individual differences were explored further with detailed interviews, …a task analysis and a detailed questionnaire. Areas of significant agreement among inspectors were found, as were responses that differentiated high from low performing inspectors. Rasmussen's skill/ rule/ knowledge classification was used to aid the analysis of these latter studies, showing the contribution of higher-level cognitive processes to the inspection task. Show more

Keywords: inspection, performance, defects, interviews, questionnaires

DOI: 10.3233/OER-2004-4105

Citation: Occupational Ergonomics, vol. 4, no. 1, pp. 51-65, 2004

Article Type: Meeting Report

DOI: 10.3233/OER-2004-4106

Citation: Occupational Ergonomics, vol. 4, no. 1, pp. 67-68, 2004

Article Type: Calendar

DOI: 10.3233/OER-2004-4107

Citation: Occupational Ergonomics, vol. 4, no. 1, pp. 69-69, 2004