This research examines changes in wrist kinematics associated with practice in the use of two computer pointing devices (mouse and trackball). A multiple case study of six participants was employed. The use of pointing devices may lead to musculoskeletal discomfort and injury as a consequence of prolonged or repetitive exposure to postures involving wrist extension and ulnar deviation (Burgess-Limerick et al., 1999). Humans may adapt to different pointing devices with practice although the form and consistency of any adaptation or whether such adaptations occur as a response to discomfort is unknown.

Wrist flexion/extension and radial/ulnar deviation was measured while six participants completed four standardised tasks and a practice task each day for ten days using two different pointing devices (mouse and trackball). Each pointing device was employed in two, quasi-randomly assigned, five day blocks. Participants were all experienced mouse users. The standardised tasks involved horizontal and vertical cursor movements completed before and after the practice period each day.

Exposure to extreme ulnar deviation and wrist extension was minimal throughout data collection. Adaptive responses were evidenced as a result of trackball practice however considerable individual differences were observed. Minimal adaptation observed with mouse device use.

Preliminary results suggest that learning adaptations primarily occur due to an ability to release degrees of freedom in the movement rather than any apparent discomfort. All participants demonstrated some level of adaptation through practice, though specific adaptations were manifestly different between participants. Adaptations were particularly evident with an unfamiliar pointing device (trackball). Practice may improve pointing device performance but may not be of benefit in reducing time spent in wrist postures likely to cause discomfort or injury.

Burgess-Limerick et al. (1999). Journal of Clinical Biomechanics, 14, 280-286.