Narrow Results

A methodology was established to investigate the contact mechanics of the thumb and the index finger at the digit–object interface during precision pinch. Two force/torque transducers were incorporated into an apparatus designed to overcome the thickness of each transducer and provide a flexible pinch span for digit placement and force application. To demonstrate the utility of the device, five subjects completed a pinch task with the pulps of their thumb and index finger. Inter-digit force vector coordination was quantified by examining the (1) force vector component magnitudes, (2) resultant force vector magnitudes, (3) coordination angle: the angle formed by the resultant vectors of each digit, (4) direction angle: the angle formed by each vector and the coordinate axes, and (5) center of pressure locations. It was shown that the resultant force magnitude of the index finger exceeded that of the thumb by 0.8 ± 0.3 N and that the coordination angle between the digit resultant force vectors was 160.2 ± 4.6°. The experimental apparatus and analysis methods provide a valuable tool for the quantitative examination of biomechanics and motor control during dexterous manipulation.

The wrist and thumb postures adopted during the use of three different types of computer mouse (mini mouse; standard mouse; MouseMan) to perform eight standardized tasks were evaluated. Thirty elementary students between seven to twelve years of age were studied using a magnetic tracking system. The peak value and angular range of motion of the wrist and thumb extension/flexion and radial/ulnar deviation were measured during performing 8 standard tasks. There were statistically significant larger values in the standard mice with regard to extreme wrist extension. Angular range of wrist extension observed for the standard mice were also much higher than the mini mouse and MouseMan. There were statistically significant larger values in the MouseMan with regard to extreme wrist ulnar deviation, and an average decrease in extreme thumb flexion and angular range of thumb flexion. The results from the questionnaire showed that most elementary students preferred to use the standard mouse (40%) next was the MouseMan (37%); and the last the mini mouse (23%). The recommendation of mouse types based on the hand length for elementary students was not statistically significant in our study.