A-25 ソフトボールの打撃で飛翔中に打球の軌道を変化させるインパクト特性(バットとボールとのインパクト)

Abstract

The purpose of this study was to examine the three-dimensional kinematic parameters of ball impact that cause the phenomenon of the lateral deviation of the batted ball. Nineteen women's collegiate softball players performed four "free-batting" trials with maximal effort to project the batted ball toward various directions; fly or line drive toward same field, grounder toward same field, fly ot line drive toward opposite field, and grounder toward opposite field. Behavior of the ball impact was recorded with two high speed cameras (1000 fps). Three-dimensional trajectory of the batted ball was calculated using the initial condition of the batted ball (velocity of the batted ball, spin rate, orientation of spin axis) immediately after impact. The projection angles of the bat on the horizontal plane (horizontal bat angle), the vertical plane (vertical bat angle) and the angle from horizontal of the line of impact (line of impact angle) were determined at the ball impact. Laterally-deflected distance of batted ball in opposite-field hitting (6.01±1.85 m) was longer than same field hitting (2.23±1.75 m). Meanwhile, within-group variance of laterally-deflected ratio (laterally-deflected angle per second) varied widely. The laterally-deflected ratio was correlated with the horizontal bat angle and the line of impact angle, but the vertical bat angle was not. The results indicate that the laterally-deflected ratio of the batted ball was increased by if the impact surface of the bat is facing toward the direction of the batted ball at the instant of ball impact.