Effects of Space Restrictions and Mouse Locations on Upper Extremity Kinematics and Muscle Activity during Computer Tasks

Abstract

People spend an average of 37.5 hours/week on their computers, totalling 1800 hours annually (Noack-Cooper, K. L. et al., 2009). Spending >4 hours daily on a computer demonstrates increased MSD risk, such as carpal tunnel syndrome (Ardahan, M., & Simsek, H., 2016; Manktelow, R. T. et al., 2004). Work-from-home scenarios can lead to make-shift workstations, with space restrictions. The purpose of this work was to quantify upper extremity muscle activity and posture during computer tasks, when people are exposed to restricted environments. 18 healthy university-aged participants (8 Male, 10 Female) were recruited. Participants were outfitted with surface electromyography on 16 muscles of the trunk/right upper extremity, and 13 reflective motion capture markers. Two mouse-based tasks were completed using AimLab: 1) a point-and-click task, and 2) a mouse tracing task. Tasks were completed in four common mouse locations in both restricted and unrestricted boundaries. Supraspinatus, upper trapezius, and middle trapezius demonstrated significant increases in muscle activity between both tasks. Right middle (SUPR: 64.1 ± 17.2 %MVE; UPTR: 3.5 ± 0.8 %MVE; MTRP: 12.9 ± 4.4 %MVE), and front keyboard (SUPR: 71.5 ± 19.6 %MVE; UPTR: 3.5 ± 0.7 %MVE; MTRP: 16.0 ± 5.3 %MVE) locations produced the greatest amount of muscle activity in both conditions. Restricted conditions across locations increased joint angles across the shoulder, elbow, and wrist joints. Lateral and deep mouse locations created increased shoulder extension and abduction across both conditions. Participant accuracy was greater in the restricted conditions (PC: 96 ± 5.3%; Track: 84.9 ± 10.7%) compared to unrestricted (PC: 95.4 ± 5.8%; Track: 81.4 ± 8.9%). Increases in muscle activity were found across all locations and conditions for the shoulders and upper back, with the restricted condition demonstrating the greatest increase in activity. This could suggest that increased discomfort and musculoskeletal complaints are probable when working in a restricted environment for extended periods of time. Utilizing the front edge of the desk as a mouse location decreased muscle activity, which may provide rest of relief from muscle overuse.