Abstract
Musculoskeletal disorders are common among workers who use powered hand held tools in assembly industry. The present study was carried out at a bus assembly plant where pneumatic nutrunners are the dominant powered hand tool. The activity in five muscles was measured for different phases of the securing, comparing soft and stiff joints, three different joint positions, and two powered tools. The aims were to characterize the muscular load during usage of the chosen tools, and to be able to provide relevant information to the production engineers, who were to design a new production system. The variance in muscular activity was large, both within subjects and between the mean curves of different subjects. Still, it was possible to obtain characteristic shapes of EMG curves sampled under different conditions. EMG peaks were seen in the hand extensor muscles for the right-angled tool. Joint position strongly contributed to differences in muscular activity in all muscles, which together with the finding that the tools made very small differences, were regarded as the most valuable results for the production engineers.
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