FACTORS DETERMINING THE SPIN AXIS OF A PITCHED FASTBALL

Abstract

In order to make hitting more difficult for a batter, the pitcher introduces spin and alters the trajectory from a simple parabolic trajectory to one in which the aerodynamic force plays a significant role (Alaways and Hubbard, 2001). Although the direction of the spin axis greatly affects the lift force acting on the ball (Jinji and Sakurai, 2006), no study has been reported on how the spin axis of a pitched ball is determined in pitching motion. The purpose of the present study was to investigate the factors that determine the direction of the spin axis of the baseball. It is expected that movement of the upper extremity relates to the direction of the ball spin axis (Chin et al., 2009). The present study focused on the orientation of a pitching hand in a global coordinate system.