The aim of this study was to investigate the trade-off relation between the speed and accuracy of a pitched baseball. To do this, the initial velocity of the ball at release and the distance between the arrival position of pitched ball and the target were measured at the four different subjective effort levels. Three baseball pitchers each performed 12 sets of 16 pitches at subjective effort levels of 100％, 90％, 70％, and 50％; in each of the sets, the target was set at a different height above home plate. Each pitcher threw 192 pitches in total. The pitching motion and trajectory of the ball were videotaped with a high-speed video camera and normal video camera, respectively, and analyzed by three-dimensional direct linear transformation. The following results were obtained. Although there were individual differences between participants, the initial velocity of each pitched ball at subjective effort levels of 100％, 90％, and 70％ was over 90％ of the participantʼs maximum velocity, and in general, the accuracy of the pitch and initial velocity of the ball at release had a trade-off relation: accuracy increased with decreasing initial velocity. However, at the 50％ subjective effort level, the opposite relation was observed: accuracy decreased with decreasing initial velocity. As the subjective effort level was reduced, all the participants changed their pitching motion at a certain subjective effort level. This change in pitching motion possibly caused the pitchers to change their technique for releasing the ball, and consequently the trade-off relation no longer held.
