126 Effects of breaking ball on the states of ball-release and the motion during baseball pitch

Abstract

The purpose of this study was to investigate the difference of joint motion and state of ball-contact between the pitches of fastball and breaking ball. The joint motion of upper limb, trunk and lower limb during baseball pitch were measured by accelerometers and gyro sensors. The state of ball-contact was measured indirectly by eight strain gauges attached to the surface of nail of 2nd and 3rd finger. Four subjects belonged to a college baseball team participated in this study and pitched fastball and breaking ball such as slider, shoot, forkball and curve ball five to ten times. Measuring with the sensors mentioned above, the angular velocities of joint motions and the strain of nail during the ball-contact were obtained directly or calculated. Those were rotation and tilting forward of trunk, rotation of hip, swing of forearm and upper arm, pronation of forearm, internal rotation of shoulder, rotation and swing of both side thighs, and left leg. As the results of analysis of the joint motion and the strain of nails, the following were clarified. The joint motions during the pitches of slider were similar to those during the pitches of fastball. The timing of ball-release of fastball pitches were later than that of slider pitches, and were earlier than that of shoot pitches. The strain of nail during the pitch of fastball was larger at nail tips called 'N' in this study. During the pitch of slider, the strain was larger at radial side of nail called 'W' in this study.