The Influence of Ball Size and Weight on the Lag Period of the Upper Arm in Overhand Throwing

Abstract

The key component to maximizing velocity in overhand throwing is proper proximal to distal sequencing of the body. It is known, however, that objects that are too heavy to be thrown in this manner will be tossed in a more simultaneous manner, eliminating the lag period between adjacent segments. Yet, there is little research on the effect of ball size and weight on the lag between segments, particularly between the shoulder and trunk, which is of critical importance in throwing mechanics. PURPOSE: To investigate the effect of different size and weighted balls on the time period between forward movement of the trunk and forward movement of the upper arm, as denned by the elbow. METHODS: Thirteen participants (m = 10, f = 3) considered experienced throwers, were asked to throw three different weighted baseballs and softballs (4oz, 7oz, 12oz) of regulation diameters (9 inch & 12 inch circumference, respectively), with the balls randomly assigned to avoid learning effects. Participants were asked to throw the ball as “hard as they could” into large net placed in front of them. The upper arm lag period was analyzed using a custom (Motion Reality Inc., Atlanta Ga) 6 camera motion capture system, with markers interspersed throughout the upper body. RESULTS: A 2 (size) x 3 (weight) within subject repeated measures ANOVA revealed a size main effect (p = .043, power = .548) and a size-weight interaction (p= 0.049, power = .559), but no main effect for weight. CONCLUSIONS: The results of this study suggest that the size of the ball has a greater effect than the weight of a ball when propelling an object in a sequential manner. This finding supports the hypothesis that experienced throwers will revert to more simultaneous (or push) motions for objects that are too large for them to throw comfortably. Thus, suggesting that grip may play a role in determining the motor program employed by the thrower.