The role of an Accuracy Restriction on the Separation Time between the Pelvis and the Trunk in Baseball Pitching

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Abstract

The purpose of this study was to determine whether a change of an accuracy restriction (AR) leads to a change in the separation time between the peak rotational velocities of the pelvis and the trunk during a pitching motion, while the ball velocity is kept constant. The peak rotational velocities of the pelvis, trunk, the separation time and ball velocity were measured on ten players (age: 20.4±2.4 years, length: 187.6±4.7 cm, bodyweight: 81.3±9.7 kg, pitching experience: 10.7±4.2 years). They performed two tasks twice. First, they had to perform ten fastballs on a large target with a low accuracy restriction. Secondly, they had to perform ten fastballs on a small target with a high accuracy restriction. A week later they performed the same tasks but in reversed order. The associations between the kinematic variables and the accuracy restriction were separately determined using generalized estimating equations. The rotational velocity of the pelvis was significantly associated with the accuracy restriction. The separation time and rotational velocity of the trunk were not significantly associated with the accuracy restriction. It cannot be concluded that the separation time was affected by a change in accuracy restriction.