A-15 Generating mechanism of racket head-speed for the upper limb in tennis serve motion : The influence of skill level on the contributions in forward dynamics analysis
Details
The purposes of this study were to quantify the contribution of the upper limb joint torques and shoulder joint reaction force to the racket head speed and make clear the generation factor of motion dependent term during tennis serve motion. The upper limb segments and racket were modeled as a system of 4-rigid linked segments. The axes of the elbow and wrist joints were modeled by a two-axis re volute joint to consider the degree of freedom (DOF) of the joint, and the hand was considered to be connected with the racket via zero DOF joint. The equation of motion with respect to the upper limb and racket was obtained from the equation of motion for each segment and from equations for constraint condition in which adjacent segments are connected by joint, and from constraint axes equations for elbow and wrist joints. The dynamic contributions of the joint moments, shoulder joint force, motion dependent term and gravity term to the racket head speed were derived from the dynamic equation of the system. Collegiate male tennis players' motion were captured by VICON 612 system (9-camera, 250Hz). The results obtained in this study show 1) not only joint moments but also motion dependent term make significant role for generating racket head speed during forward swing motion in tennis serve, and 2) shoulder internal external rotation torque is most important factor of generating motion dependent term.
