Swinging a baseball bat at a pitched ball takes less than half of a second. A hitter uses his lower extremities to generate power, and coordination of the swing motion gradually transfers power through the trunk to the upper extremities during bat-ball impact. The most important instant of the baseball swing is at the bat-ball impact, after which the direction, speed, height, and distance of the hit ball determines whether runs can be scored. Thus, analyzing the biomechanical parameters at the bat-ball impact is useful for evaluating player performance. Different motion-capture systems use different methods to identify bat-ball impact. However, the level of accuracy to detect bat-ball impact is not well documented. The study aim was to examine the required accuracy to detect bat-ball impact timing. The results revealed that ±2 ms accuracy is required to report trunk and hand kinematics, especially for higher-order time-derivatives. Here, we propose a new method using a hand-worn inertial measurement unit to accurately detect bat-ball impact timing. The results of this study will be beneficial for analyzing the kinematics of baseball hitting under real-game conditions.
Keywords: IMU; acceleration; accuracy; batting; kinematics.