Measurement of maximum voluntary pinch strength: effects of forearm position and outcome score.

The purpose of this study was to determine the effects of forearm position and outcome score on key, fingertip, and three-jaw chuck pinch strength. Maximum voluntary key, fingertip, and three-jaw chuck pinches were performed by 135 healthy adults (20-88 years old) three times in a pronated, supinated, and neutral forearm position with the right and left hand using a B&L (B&L Engineering, Tustin, CA) pinch gauge. The highest, first, and mean scores of three pinch forces were recorded. Three 3 x 3 factorial repeated-measures analyses tested each type of pinch strength. Forearm position affected key and fingertip pinches (p<0.017; effect sizes <0.14) but not three-jaw chuck pinch. The highest score ranked highest followed by the first and then the mean of the three scores (p<0.017; effect sizes >0.53). Although the effects of type of outcome score were consistent, the statistically significant effects of forearm position and outcome score may be too small (<1 lb) to be clinically relevant. Standardized positioning during pinch strength measurement is still recommended despite these findings.