Evaluation of wrist posture during the operation of four electromechanical mice

This research investigated the effect of mouse support height, mouse type, and hand length on the wrist posture of computer mouse operators. Mouse support height was defined as the distance from the floor to the horizontal surface on which the mouse is supported and divided into three levels: 95%, 100%, and 105% of the seated elbow height. The levels of mouse type were the Logitech MouseMan, Kensington Thinking Mouse, Apple Desktop Bus Mouse, and the Apple Desktop Bus Mouse II. Hand size was defined as the distance from the stylion landmark on the right hand to the tip of the middle finger. The twenty-four subjects were divided into three groups of eight according to hand size (small, medium, and large).

The average distance in degrees from neutral was calculated for the first set of dependent measures. Results showed that an increase in the mouse support height caused a decrease in the amount of wrist extension and an increase in the amount of ulnar deviation for both pointing and dragging tasks. There was also a significant interaction between mouse support height and hand size for wrist extension during pointing tasks.

Mouse type and hand size were not found to be significant as main effects in either pointing or dragging tasks. It was probable that the differences in the physical characteristics of either the user's hands or of the mice were not great enough to affect the posture of the user.

For the second set of dependent measures, wrist posture was divided into intervals that ret1ect the severity of posture. Mouse support height was found to significantly affect the amount of time spent in different posture intervals. The remaining independent variables did not significantly effect these dependent measures.