A-37 Racket Speed Generating Mechanism during Tennis Serve Motion in Consideration of Muscle Force Generating Characteristics

Abstract

The purpose of this study was to quantify the dynamic contribution of racket side arm muscles in consideration with muscle contraction types in tennis serve motion. In order to assess dynamic contribution of individual muscle forces, a musculoskeletal model with 144 muscle elements was constructed by using the SIMM software, and the contributions of muscle forces of the racket side arm to the racket face speed at impact and to the shoulder joint angular velocity were obtained from a dynamics analysis based on the equation of upper-body motion with consideration of the generating factors of the motion dependent term. Male collegiate athletes, participated as subjects in this study, performed first services. Trajectories of markers on the body and ground reaction forces were measured with VICON-MX system and a force plate, respectively. The results obtained in this study indicate that 1) the concentric muscle torque of clavicle part of deltoid and subscapularis via shoulder internal/external rotation axis was great contributor to the racket face speed, 2) the shoulder external rotation angular velocity inducing eccentric internal rotation torque was generated by concentric muscle torque of clavicular part of deltoid, infraspinatus, teres minor, and coracobrachialis and by eccentric muscle torque of clavicular part of deltoid and coracobrachialis, and 3) contributions of concentric components of individual muscle forces are greater than those of eccentric components. It must be noted that the results depend on the object function and parameters used in the musculoskeletal model.