Grip Strength as a Function of Forearm Rotation and Elbow Posture

An investigation was performed to assess the effect of forearm rotation (pronation and supination) and elbow orientation upon maximum grip strength of 10 male and 10 female subjects. Seven positions of forearm rotation which ranged from 90 degrees pronation to 90 degrees supination in both the 90 degree elbow flexion (arm adducted, forearm horizontal) and 0 degree flexion (shoulder flexed, whole-arm extended forward and horizontal) postures were examined. Thus a total combination of 14 postures were documented. Results indicate that maximum grip strength decreased significantly with forearm pronation, relative to the “neutral” forearm posture (p = 0.086). Other rotation postures did not yield significantly different grip strength from the neutral, but there was a clear decreasing trend in grip strength with forearm rotation away from neutral, particularly in pronation. The 0 degree elbow flexion showed the highest average grip strength values compared to 90 degree elbow flexion postures. Also, in the 90 degree elbow flexion posture, grip strength tended to increase with some supination from neutral rotation. It is recommended that for repetitive grasping activities, the arm and forearm postures should be considered in evaluating maximum grip strength. A regression model is presented to estimate maximum grip strength as a function of forearm rotation and elbow posture.