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The Effects of Differing Overhead Heights on Shoulder Fatigue during a Repetitive Intermittent Task

The purpose of this study was to determine the effect of different overhead work heights on shoulder fatigue. Ten participants (6 males, 4 females) with manual work experience were recruited to perform a dynamic intermittent overhead task simulating automotive assembly work. Participants performed a keyboard tapping task using a hand tool at three different heights, relatively to individual anthropometry, for up to one hour. Throughout the trials, electromyography (EMG) was recorded from three shoulder muscles (anterior deltoid, middle deltoid, and trapezius), and subjective ratings of perceived discomfort (RPD) were obtained. Key striking accuracy was used as a measure of task performance. Though results were not always statistically significant, the EMG, RPD, and performance measures all indicated that higher working heights generally lead to more rapid onset of fatigue.