Abstract
The purpose of this study was to determine the effect of moving closer to the work while performing overhead drilling. This task was simulated by twenty subjects while standing on either a lower or a higher step of a stepladder. Shoulder load was estimated by root-mean-square amplitude of electromyographic (EMG) activity and cinematographic analysis to determine shoulder joint moment using static link segment modeling. The results indicated that moving closer to the work surface by moving up a step reduces shoulder joint moment and anterior deltoid EMG. However, biceps brachii EMG increased by moving up a step. There was no significant change noted in EMG median frequencies suggesting that fatigue was not a significant factor. We conclude that while moving up a step reduces the muscular load on some muscles and the shoulder joint, other muscles may work harder. There are also safety considerations regarding moving up a step and alternative methods to move closer to the work surface are suggested.
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