Physiological workload evaluation of screw driving tasks in automobile assembly jobs

Abstract

For ergonomic intervention of manual materials handling (MMH) tasks, biomechanical, physiological, and psychophysical approaches have been studied. In the automobile assembly jobs. however, very few studies on physiological stresses have been carried out, whereas many studies have been reported in biomechanical and postural stresses. In this study, physiological workloads were evaluated during screw driving tasks in the automobile assembly line. The effects of load and work postures on heart rate, oxygen consumption and subjective ratings (5-point scale) during a screw driving task were studied using nine male subjects, with a within-subject design. Heart rate and subjective ratings of all nine subjects and oxygen consumption of five subjects were evaluated during a simulated screw driving task with varying loads (8.2 kg 16.4 kg), leg postures (standing and squatting) and trunk postures (forward flexion, forward flexion with lateral bending and twisting). The effect of load, leg and trunk postures were found to be significant on heart rate, oxygen consumption and subjective rating. Heart rate and subjective ratings showed a high correlation for all the combined conditions. For screw driving tasks, it is recommended to redesign work methods in order to avoid squat sitting, lateral bending and twisting. Relevance to industry Automobile assembly job is one of the most labor-intensive industries and workers often perform their tasks in poor working postures repetitively due to constrained work places. This study was conducted to evaluate the physiological workload of screw driving tasks in awkward working postures, such as laterally bent and twisted trunk and squat sitting. Ergonomic guidelines for such assembly tasks were recommended based on the results of a laboratory experiment. (C) 2001 Elsevier Science B.V. All rights reserved.