SEGMENTAL CONTRIBUTIONS TO BALL VELOCITY IN THE OVERHAND THROW

INTRODUCTION The overhand throw is a skill common to many sports. As important as it is, little is known about how the segments contribute to throwing velocity across skiU levels of developmentally mature throwers. The purpose of this study was to examine the relative contribution of the legs, trunk, arm, and hand to overhand throwing velocity across several skill levels. METHODS One hundred and one subjects with wide ranging experience in throwing for maximum velocity in sport activities participated in the study. Seven subjects were eliminated due to the use of an observed "push" in their throwing technique. The data for the 94 remaining subjects (75 male, 19 female, mean age: 22.63b2.36 years) were analyzed. To determine the contribution of the selected segments to throwing velocity, all subjects randomly performed 4 different maximal throws: 1) a normal, whole body throw (WBT); 2) a throw in which the legs could not contribute, but the trunk, arm, and hand segments could follow typical motions; 3) a throw in which the legs and trunk could not contribute, but the arm and hand segments could follow typical motions; 4) a throw that only allowed contribution from the hand. Each subject threw standard size and weight baseballs in all four conditions until a minimum of three acceptable throws were recorded. A radar gun was used to measure all throwing velocities. The contribution of the legs, trunk, and arm were calculated from differences between each of the four aforementioned throws. Relative contributions of the selected segments were calculated by dividing by the WBT value. METHOD A MANOVA was performed to compare the performance of the males and females. No significant differences were found. After combining the females and males into one group, subjects were divided into 3 groups based on percentile score. The low velocity group had 32 members, the medium velocity group had 30 members, and the high velocity group had 32 members. Results of the multiple, one-way ANOVAs indicated that significant differences (p<0.05) existed between groups for all four relative contributions. Scheffe post-hoc tests revealed the high velocity group had significantly greater relative leg contribution than the low velocity group. The high velocity group also had significantly greater relative trunk contribution than both the medium and low velocity groups. For relative arm contribution, however, the high velocity group had significantly less contri bution than the low velocity group. For relative hand contribution the high velocity group and the medium velocity group had significantly less contribution than the low velocity group. CONCLUSIONS In general, it was found that as ball velocity increased the relative contribution of the legs and trunk increased, while the relative contribution of the arm and hand decreased. While it is not possible to attribute what differences were due to factors like muscle fiber type, strength, or technique, it is possible to suggest that the body may require different segmental emphasis for greater throwing speed. Perhaps arm and hand velocity contributions are limited by a ceiling effect and the legs and trunk are not. It appears that better throwers generate velocity more from the legs and trunk, which generate velocity with long axis rotation and translation of the entire body, than from the arm and hand.