Induced motion analysis of upper body in baseball batting: (Changes in bat-motion generating mechanism between inside and outside hitting-points)

The purpose of this study was to investigate the changes in the bat-motion generation mechanism in baseball tee batting at different hitting points during induced speed analysis of baseball whole-body batting motion. The whole-body with bat was modelled as a system of 16-rigid linked segments. One male experienced baseball player, who has 10-year experience and was right-handed hitter, performed a baseball tee batting. He was instructed to hit a teed ball set at his belt height and placed at 3 locations (inside, center and outside) toward the net as strong as possible placed in 3 directions (left, center and right). The motions were captured with a motion capture system, and kinetic data were measured with 2 force platforms and an instrumented bat. The results obtained in this study showed that the flexion-extension torque at the knob-side shoulder joint showed large positive contribution rather at inside ball batting than that at outside ball batting, and that the flexion-extension torque at the knob-side elbow joint was negative contributor to the generation of bat head speed rather at inside ball batting than that at outside ball batting when focusing on upper-body.