A New Approach for Assessing Kinematics of Torso Twist in Baseball Batting: A Preliminary Report

The motions of segments involved in striking and throwing events are generally sequenced in a proximal-to-distal fashion (Putnam 1993). Welch et al. (1995) analyzed baseball batting using a rigid-body-link model with a two-segment torso, and indicated the importance that the lower torso starts rotation in the direction of pitcher before the upper torso, which, in turn, should start before the arm segments. Also, this sequential motion is considered to allow the kinetic link system to generate synergy between the musculature of the torso and upper extremity. Specifically, the upper torso is expected to have an important function to accelerate distal upper extremity and bat. However previous studies employed a two-segment torso model and the influence of the motions of the shoulder-girdles to the torso’s sequential action for twisting was ignored. In the present study, torso’s sequential twisting was analyzed with a three-segment torso model, and the kinematics of torso twist in baseball batting was evaluated.