Effect of grip span on lateral pinch grip strength.

Repetitive, high-force pinch grip exertions are common in many occupational activities. The goal of the current study was to quantify the relationship between lateral pinch grip span (distance between thumb and index finger) and lateral pinch grip strength. An experiment was conducted in which 40 participants performed maximal lateral pinch grip exertions at 11 levels of grip span distances (0, 10%, ... 100% of maximum functional lateral pinch grip span distance). The results show a significant effect of lateral pinch grip span, with strength at the maximum functional lateral pinch grip span 40% higher than that found at the smallest lateral pinch grip span considered. Between these two endpoints, strength increased monotonically with increasing pinch grip span. The application of these results in pinch grip design criteria for both high-force and long-duration exertions is discussed. Potential applications of this research include the design of hand tools and controls for which significant force is applied by the user.