Computer mouse and track-ball operation:: Similarities and differences in posture, muscular load and perceived exertion

Posture (optoelectronic 3D motion analysis system), muscular load (EMG), perceived exertion (rating scales), preference and productivity were investigated in 20 healthy VDU-operators (10 male and 10 female) during text editing with two different data input devices, a mouse and a track-ball. Work with the track-ball entailed lower shoulder elevation and less neck/shoulder muscle activity than work with the mouse. Arm support reduced muscle activity in the neck/shoulder region irrespective of input device used. A table height lower than 3 cm above elbow height allowed arm and shoulder support without undue shoulder elevation. Work with the track-ball entailed more wrist extension than work with the mouse. Perceived exertion ratings were lower for the shoulder and higher for the hand with track-bait than with mouse operation. Thus, biomechanical demands differ between different input devices. The women elevated and rotated their right shoulder outwards more than the men during work with both input devices. The overall EMG results showed a higher activity among the women than among the men in two of the examined muscles. This may relate to anthropometric differences which also influence biomechanical load moments. Another reason could be the observed differences in working techniques between the men and the women. Relevance to industry The design of input devices affects levels of muscular load in neck/shoulder and hand/forearm muscles. Joint positions differ depending on the size and design of the input device and the operators' anthropometry. The design of input devices should be adapted to the differences in work tasks and variations of human dimensions in order to avoid injuries and to enhance the effectiveness of VDU work. (C) 1999 Elsevier Science B.V. All rights reserved.