This study aims to examine the mechanism how ball spin rate is controlled by fingers torque and power during fastball and curveball pitches. Participants were eight baseball players. Finger kinetics was calculated by an inverse dynamics method. In fastball pitch, peak fingers flexion torque and its power in high spin rate pitchers was smaller than that of low spin rate pitchers with similar ball velocities (n=3). Contrast to fastball, in curveball pitch, peak fingers flexion torque in high spin rate pitchers was larger than that of low spin rate pitchers with similar ball velocities (n=2). These results suggest that fingers flexion movement is less effective for producing ball spin rate during fastball pitching. On the other hand, it is considered that producing large fingers flexion torque just before ball release leads to imparting greater topspin to the ball.
