Paper Title
Pitching Analysis of Body Variables According to Ball Velocity in Amateur Baseball Pitchers Using Gyro Sensor.

Abstract
In baseball, pitching with maximum ball velocity is an important factor for a pitcher's success. Some studies have used the inertial sensors in a manner to compensate for these limitations of the motion capture system for obtaining kinematic data. For this reason, inertial sensors (gyro sensor) were also used in this study to analyze body variables during pitching performance. Thus, the purpose of this study was to examine the correlation of ball velocity with body variables in eight amateur baseball pitchers. In this study, they performed 10 to 15 maximal fastball pitch trials. Pitching velocity was measured by speed gun. The wearable gyro sensor was used to investigate the body variables (horizontal abduction and abduction of shoulder, trunk rotation angle (anterior and posterior), trunk rotation angular velocity, food direction, stride length) during the pitching performance. The mean and standard deviation data from the eight amateur pitchers was used for data analysis. We calculated a Pearson correlation coefficient to determine the associations between ball velocity and body variables. According to result, ball velocity significantly correlated with the horizontal abduction and abduction of shoulder at arm cocking, torso angular velocity and stride length (p<0.05). When the external rotation is greater, stronger shoulder contraction may occur due to the action of stored elastic energy, the myotatic reflex, and a greater rate of force production during pre-stretched and contracting muscles during arm acceleration phase. For stride length, it is regarded a not only critical kinematic factor for determine the timing of kinetic chain events but also transitioning energy to the pitching arm from lower extremity. As increased trunk rotation angular velocity, levels of trunks action develop more advanced and led to increases in energy transfer to the pitching arm. Thus, these body variables should be considered to increase the ball velocity, which is an important ability of the baseball pitcher in training and rehabilitation. Keywords- Gyro, Baseball, Pitcher, Ball velocity, Kinematics, Biomechanics