Effects of Grip Span, Wrist Position, Hand and Gender on Grip Strength

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Abstract
Extensive literature is available which has examined the effects of grip span, wrist position, hand, gender, and anthropometric dimensions on grasp strength, but none have looked at all the factors combined. A thorough understanding of the relations between these various factors would help minimize workplace risks and improve safety. Thus, a study was performed to relate these factors. Twenty subjects (10 male and 10 female) performed maximal exertions with both hands in three wrist positions (45° flexion, 45° extension, and neutral), for three Jamar hand dynamometer spans. Thus, the model was a 2 (gender) x 2 (hand) x 3 (wrist position) x 3 (dynamometer span) x 20 (subjects) mixed effects model with blocking on subjects. Anthropometric dimensions of the subjects' hands were utilized to establish correlation between basic hand dimensions and grasp strength. A stepwise regression analysis established correlation between basic hand dimensions with grasp strength. An R2 value of 0.82 was obtained for the regression equation developed for the largest span (6 cm) of the dynamometer with palm thickness, wrist circumference and forearm length as the independent variables and grasp strength as the dependent variable. For the middle span of 4.7 cm, however, it was seen that palm thickness, wrist circumference, and hand breadth were the only significant variables, with a coefficient of determination of 0.79. Therefore, these four dimensions were chosen for a correlation study with grasp strength. The correlation study revealed that wrist circumference has a reasonably good correlation between the non-dominant hand and the largest span of the handle in the neutral wrist position. Palm thickness and hand breadth yielded significance in two of the three handle spans. The ANOVA showed that all main effects, namely, wrist position, grip span, gender, and hand were significant at the 0.01 level.