Meeting Abstract

P1.99  Tuesday, Jan. 4  The relative contributions of the body and the throwing arm to throwing velocity in softball and baseball players. MAKI, J.M.*; PONTZER, H.; Washington University in Saint Louis; Washington University in Saint Louis julmaki@gmail.com

Accurate, high velocity throwing is a skill unique to the human lineage, important for hunting during our history as hunter-gatherers. Throwing in human ancestors has been examined primarily through the skeletal anatomy of the shoulder and arm, and it has not been examined to what degree the remainder of the body contributes to the velocity of the throw. As most athletes know, a great deal more velocity can be achieved by propelling the body forward during the throw, and this may outweigh the effects of variation in the arm. This study aimed to parse out the relative contributions of the arm and the body during a standard overarm throw. Kinematic data were collected for thirty baseball and softball players throwing a standard softball. A 3D motion capture system using four high speed infrared cameras tracked reflective markers adhered to joint centers and the softball. Kinetic energy (E_k) was calculated for the upper body, and for the ball and arm. In addition, isometric arm strength in flexion and extension at the elbow and wrist were assessed with a compression/tension load cell. Preliminary results indicate that the contribution of the body E_k to throwing velocity ranges from 33-60%. Intriguingly, the percentage of additional ball E_k produced by the arm is negatively correlated with arm strength. Furthermore, arm strength is correlated with E_k at the shoulder, indicating a correlation between arm strength and overall body strength. Together, these results suggest that arm strength alone is a misleading indicator of throwing performance, and that research on throwing taking into account only arm anatomy may be missing the primary determinant of throwing velocity.