Abstract
In this research, the relation between the stability of the wind-up phase motion and ball control of a baseball player were examined. The subject was a pitcher of 32 years old who plays baseball several times a month. We recorded this pitcher's throwing motion with a digital video camera, and we analyzed the throwing motion using a 3D motion analysis system. In the analysis, the trunk tilt angle of the wind-up phase was calculated. Afterwards, we compared the sizes of the differences of the trunk tilt angle when ball was thrown over the same course with when the ball was thrown on other trajectories. The trunk tilt angle in the wind-up phase motion when the ball was thrown over the same course was reproduced well at each throw. It was thought acquisition of wind-up motion reproducibility was necessary for having good ball control.
