Abstract
The purpose of this study was to quantify the contribution of the whole-body joint torques to the vertical component of the bat head velocity during baseball batting motion. The segments and bat were modeled as a system of sixteen-ridig linked segments, and constraint axes of the elbow, wrist, knee and ankle joints were modeled with anatomical constraint equations in order to consider the degree of freedom (DOF) of the joint. Each hand was considered to be connected with the bat through zero DOF joint. The equation of motion with respect to the whole-body and bat was obtained from 1) the equation of motion for each segment, 2) equations for constraint condition in which adjacent segments are connected by joint, 3) equations for constraint axes of joints. The dynamic contributions of the joint moments, shoulder joint force, motion dependent term and gravity term to the vertical component of the bat head velocity was derived from the dynamic equation of the system.
