Changes in kinematics and kinetics of pitching motion with different trunk posture

Abstract

This study aimed to investigate how the changes in trunk posture affect pitching performance in experienced baseball players. The five experienced university baseball players participated in this study. We asked subjects to perform the pitching with two conditions of trunk postures, as the throws were made as usual without any instructions (NT: normal throws) and throwing with slouched posture by relaxing trunk muscles (ST: Slouched throwing). Their pitching motion was collected in an indoor room with four high-speed cameras, located in front of the pitching direction (right and left) and reverse side of the direction (right and left), with 250 fps and a shutter speed of 1/1000 sec. We calculated angular velocities and several torque components about the pitching arm and trunk. We found that, during the ball releasing phase, significant positive correlations between the hand tip velocity and the elbow extensor velocity and between the tip velocity and elbow flexor interaction torque were obtained in the NT, while in the ST, a significant positive correlation between the hand tip velocity and palm flexor angular velocity, and between was obtained. The findings indicate that the difference in the trunk posture affected pitching movement in several joints and torque exertion in the elbow joint for increasing ball releasing velocity.