抄録
The purpose of this study was to clarify the kinetic role of the upper limbs under conditions of different hitting-point heights in the baseball T-batting motion through inverse kinetic analysis. Twenty-three collegiate male baseball players' motion were captured with VICON MX system (12-camera, 250Hz), and kinetic data at each hand were collected by using an instrumented bat equipped with 28 strain gauges (lOOOHz). Three heights of hitting point (high, middle, low) were set according to the baseball rules. The joint torques and works of the upper limbs were divided into the values caused by horizontal and vertical component offerees exerted on the bat by each hand. The results show that (1) the hitting point motion of bat were modified mainly with translational movement of the bat, and a significant difference occurs in the forces of each hand in the vertical direction under the height conditions, (2) the barrel side upper limb contributes to adjust the bat height from the analysis of joint torques caused by horizontal component of bat force, (3) shoulder joints are great contributors to adjust the bat height in the down swing phase from the analysis of joint torques caused by vertical component of bat forces, and (4) the role of elbow joint of the barrel-side upper limb is to control the bat head movement because the work done by the joint was negative values.
