Effects of a Simulated Game on Upper Extremity Pitching Mechanics and Muscle Activations Among Various Pitch Types in Youth Baseball Pitchers

Background: Throwing requires proper stability and orientation of the pelvis and scapula for efficient energy transfer during pitching. Fatigue of the pelvis and scapular musculature throughout the course of a game can impair pitching performance, and place excessive demands on the throwing arm leading to injury. The purpose of this study was to examine differences in pelvis, torso, and upper extremity pitching mechanics and muscle activations between the fastball, change-up, and curveball pitches in youth baseball pitchers following a simulated game. Methods: Fourteen youth baseball pitchers with no history of injury participated. Pitching mechanics were collected using an electromagnetic tracking system. Surface electromyography data were collected on the bilateral gluteus medius and maximus; and throwing arm side latissimus dorsi, lower trapezius, upper trapezius, and serratus anterior. Participants were instructed to throw maximum effort pitches during a simulated game that provided random game situations similar to those that occur in competition. Participants were limited to 85 pitches based on age-restricted pitch counts. Data from 3 fastballs, curveballs, and change-ups thrown in the first and last innings were selected for analysis. Results: Repeated measures multivariate analyses of variance revealed that neither pitch type nor the effect of a simulated game resulted in statistically significant changes in pitching mechanics (F-(10,F-600)=0.55, P=0.85), or muscle activations (pelvic: F-(4,F-195)=0.07, P=0.85; scapular: F-(4,F-118)=0.09, P=0.52). Conclusions: The principle findings of this study revealed that pitching to the age-restricted pitch count limit did not result in altered pitching mechanics or muscle activations, and no differences occurred between the 3 pitches. These results support previous research that indicate the curveball pitch is no more dangerous for youth than the other pitches commonly thrown. This is supported by the pitcher's ability to maintain a proper arm slot during all 3 pitches and indicates that they are obtaining the spin on the ball from their grip and not by altering upper extremity mechanics.