Affiliations: University of California, Berkeley, CA,
USA | Lawrence Berkeley National Laboratory, Berkeley,
CA, USA | Joint Genome Institute, Lawrence Berkeley National
Laboratory, Berkeley, CA, USA | Department of Medicine, University of California,
San Francisco, CA, USA
Note: [] Address for correspondence: David Rempel, MD, MPH, Department of
Medicine, University of California, San Francisco, 1301 S. 46th Street, UC RFS
Building 163, Richmond, CA 94804, USA. E-mail: david.rempel@ucsf.edu
Abstract: 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.
