抄録
The aim of this study was to describe, in detail, the trajectory of baseballs pitched under game conditions. In six games of a college baseball league, all balls thrown by the pitchers on each team were recorded by using two video cameras. The trajectories of pitched balls were calculated from the video data by a three-dimensional direct linear transformation method. The initial ball velocity, the variation of trajectories, and arrival position of pitched ball were calculated. The results were as follows. 1) Most pitchers threw types of pitches with two or three clearly different ball trajectories, but some pitchers did not. 2) Batters hit balls only in or near strike zone. When thrown a breaking ball, batters occasionally swung at balls below the strike zone. Batters must rapidly make an exact judge on the ball's trajectory, especially for low balls. 3) For some pitchers, the trajectory of fastballs was correlated with arrival position, which should be considered by batters 4) For some pitchers, the initial ball velocity or the vertical variation of trajectory decreased as the pitch count increased. However, this trend was not observed for pitchers who threw a complete game.
