THE EFFECTS OF OVERLOADING ON THROWING MECHANICS

Abstract

In baseball. the incidence of injury to the external rotator (ER) muscles of the throwing shoulder in pitchers is common. Injury to this muscle group has been found to occur primarily after the ball is released. At that instant, the major role of the ER muscles is to eccentricallly contract whereby causing the rapidly moving arm to come to a gradual halt. Because of the repetitious nature of pitching, the ER muscle group fatigues quickly increasing injury potential. The purpose of this research was to develop an effective method of overloading the throwing arm throughout the entire pitch sequence without altering pitching mechanics. In the long course, the application of overload to the throwing arm is hypothesized to increase the eccentric strength of the ER muscles allowing for more efficient, less stressful follow through. Six male collegiate pitchers served as subjects in this investigation. At random, each subject threw six fastballs from an indoor pitching mound constructed to collegiate specifications. Three pitches were thrown while wearing a 7 ounce skin-tight glove on the throwing hand and three pitches were thrown without the added overload. Three-dimensional high-speed videography (200 Hz) was used to determine x, y, and z coordinate positions of joint markers. Utilizing this data. kinematic computations were performed to define motion of upper arm segment, lower arm segment, shoulder segment, and torso. Forces and moments for both the elbow and shoulder of the throwing arm were then calculated for the entire pitch sequence. The effects of overload on the elbow exhibited an increase in elbow flexion prior to and following release. and increased decompression force at release, increased shear forces at and following release. and an increased extension moment prior to release. The effects of overload on the shoulder revealed an increase in horizontal flexion velocity after release. increased decompression force at release, increased internal rotation moment after release. and increased adduction following release. Overall, when overloading the throwing arm, slight kinetic and kinematic changes were found to occur to the elbow and shoulder. In an effort to investigate further the ability of the weighted glove to prevent external rotator cuff injuries, implementation into a long range throwing program is necessary.