The effect of two alternative arm supports on shoulder and upper back muscle loading during pipetting.

OBJECTIVE Pipetting involves static upper arm positions with the pipette held away from the body for sustained periods of time, putting increased musculoskeletal load on the shoulder and upper back. This study explores the effect of using two alternative arm supports while pipetting on muscle loading in the shoulder/neck region. PARTICIPANTS 15 experienced pipette users participated in this study. METHODS In a repeated-measures design, participants performed simulated pipetting in a laboratory setting under three arm support conditions: (1) a gel pad on the work surface, (2) a freely-moving counter-balanced forearm support, and (3) no support (control). Surface electromyography (EMG) of the anterior deltoid and upper trapezius muscles were recorded, as well as productivity and subjective usability. RESULTS Both arm support conditions resulted in significantly lower mean muscle activity of the anterior deltoid and upper trapezius muscles (p<0.001) and significantly higher subjective comfort ratings (p<0.001) compared to the control condition. The freely moving forearm support resulted in significantly lower peak muscle activity in the anterior deltoid compared to the control condition (p<0.001). Productivity was not affected by the arm supports. These findings suggest that arm support may be beneficial in reducing muscle loading and improving comfort in the shoulder and upper back during pipetting. Future studies are needed to measure the impact of these arm supports in the workplace.