Generating mechanism of bat-head velocity in baseball thrown-ball batting

Abstract

Baseball batting demands batters to respond instantaneously to balls with high speed flying from the front while they accelerate the bat head to high speed within a brief time by utilizing the motion-dependent term (MDT) effectively. During this period, time constraint occurs in the operation. However, the bat head speed generating mechanism of the baseball batting motion under such time constraint condition, assuming the game, has not been reported. Therefore, the purpose of this research was to clarify the generating mechanism of bat head speed under time constraint condition. Ten collegiate baseball players participated in this experiment being done under two types of ball conditions such as teed ball batting and thrown ball batting. Dynamic contribution analysis was carries out using a total of 16 segments of rigid body link model consisting of body with 15 segments and bat with one segment. The results obtained in this study shows (1) most of the bat head speeds at the ball impact were generated by the contribution of the MDT under the thrown ball batting condition similar to the teed ball batting condition, and (2) the timing of the contribution to the bat head speed at the ball impact was different and the SD was very large. These results indicate that the batters mainly adjusted the bat-head speed before 60% of the normalization time when the influence of the MDT became large.