LINEAR AND ANGULAR CONTRIBUTIONS TO BALL VELOCITY IN THE DELIVERY MOTION AMONG VARIOUS LEVELS OF BASEBALL INFIELDER

Abstract

The purpose of this study was to investigate the linear and angular contributions to ball velocity of the delivery motion among junior high school (group J), high school (group H), and collegiate (group C) baseball infielders by using 3D videography. A total of 54 infielders were asked to throw a baseball quickly and accurately with full effort. Our results indicated that the ball velocity increased with progression in player level (group J, 28.3 m/s; group H, 31.8 m/s; group C, 33.2 m/s). Angle and height of ball release were significantly larger in group J than in groups H and C. Contributions of the forward and upward translations of the body to the ball velocity were, respectively, 6% and 10−15%, with the rest due to the rotations of the body. These results indicate that the rotations of the body are crucial for the increase of ball velocity.