Ergonomic Mouse: Clinical Case Studies Synopses
Study 1: Comparison
A Fitts' Law Comparison Between Two Different Mouse Designs
Marvin J. Dainoff, PhD, CPE
Fellow, Human Factors and Ergonomics Society
Center for Ergonomic Research, Miami University
Mouse use has been associated with disorders of the hand, wrist, forearm and shoulder. One risk factor for the disorders associated with mouse use is the palm-down posture required to use the standard mouse. This posture requires the user to rotate the entire forearm in order to turn the hand palm-down, increasing strain on the muscles of the forearm and shoulder.
A more neutral position of the forearm and wrist is achieved if the forearm is held in the "handshake" posture, with the palm of the hand facing left (or right), rather than down. A new mouse design allows use of this more neutral posture. Previous research has confirmed that this new design does, in fact, reduce the muscle effort required while mousing. Consequently, the new mouse has significant potential for improved health outcomes.
This study compares learning rate, errors, and movement times of the new mouse and a standard mouse. Subjects pointed at and clicked on, targets of various sizes at various distances and angles of movement. The study showed that users learned to use the new mouse very quickly. There were no statistically significant differences between the mice with regard to errors. There was, however, a slight difference in movement times with the new design about 16 hundredths of a second slower.
The author concludes that this small performance cost is outweighed by the considerable benefit in reduction of user fatigue and strain previously demonstrated.
1. Presented at the 8th International Conference on Human-Computer Interaction August 22-27, 1999, Munich, Germany
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Study 2: Workload
Workload When Using a Mouse as an Input Device1
Arne Aarås, MD, PhD
Alcatel STK AS
A newly developed mouse, which seemed to give a more neutral arm posture was compared with a traditional mouse. The beneficial effect arises from a handshake orientation while mousing with the new mouse as opposed to a palm down posture with the traditional design. The muscle electrical activity was recorded for several forearm muscles while mousing with both the new and traditional designs. The new mouse was shown to significantly reduce the muscle effort required while mousing in addition to the more neutral posture. Consequently, the new mouse design was shown to be less fatiguing to use than was the traditional design.
Previous research has implicated twisting of the forearm as a causal agent in the development of musculoskeletal discomfort. Consequently, the reduction in forearm twisting while using the new mouse offers a reduction in both muscular effort and in forearm rotation, decreasing the risk of musculoskeletal discomfort.
This article also discusses previous research that has shown that non-optimal placement of the mouse increases the risk of shoulder and arm problems significantly. One study found that mouse users who placed the mouse outside an optimal area were more than six times as likely to develop upper arm and shoulder problems than were those who placed the mouse in the optimal position.
1. International Journal of Human-Computer Interaction, 9(2), 105-118.
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Study 3: Neutral Position
Can a More Neutral Position of the Forearm When Operating a Computer Mouse Reduce the Pain Level for VDU Operators?1
Alcatel STK AS
University of Oslo
A field study of a new mouse design, which gives the operator a more neutral forearm position, was compared to a traditional mouse. After using the new mouse for six months, a significant reduction in pain intensity and duration for the wrist/hand, forearm, shoulder and neck was reported in comparison to a control group. Lost-time from work was also reduced for the experimental group.
1. International Journal of Human-Computer Interaction, August, 1999
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