Human pinch-force discrimination.

Pinch-sustaining tasks such as holding a pencil, fork, or key require the exertion of different levels of force. There is little information concerning normal subjects' ability to discriminate differences in their pinching force, so the purpose of this study was to evaluate the ability of 24 normal young women to discriminate differences in their self-generated isometric tip and lateral pinching force. Resistance forces of 10, 25, 50, and 75% of known normal maximum pinching force were selected as standards. Subjects were presented a series of paired resistance settings of which the first resistance in each pair was the standard and the second resistance a comparator of some greater amount. This procedure of paired comparisons was continued until subjects' threshold of discrimination between two pinching forces was established. The results indicated that subjects' pinch-force discrimination at the standard of 50% of reported maximum pinching force was significantly better for the tip condition than for the lateral condition. This study has described an instrumentation and the methodology for assessing individuals' ability to discriminate differences in their pinching force at submaximal levels.