INTRODUCTION. “Pitching-fatigue”, considered a primary mechanism for throwing arm injuries, can impact lower body power generation to adopt compensatory stride lengths. The purpose of the study was to investigate stride length compensation impacts on brace-transfer ground reaction forces. Brace-transfer refers to the phase initiated at stride foot contact (SFC) ending at maximal external shoulder rotation (MER). We hypothesize that brace-transfer forces are affected by stride variations without impacting ball velocity. METHODS. Nineteen elite high school and collegiate baseball pitchers were randomly crossed over to throw two, 80-pitch simulated games ; (A) +25% desired stride, and (B) -25% desired stride length. Normalized stride length to body height indicated 76% and 52%, for (A) and (B), respectively. The four highest ball velocity trials per subject (Jugs Sports, Tualatin, OR) recorded by 3D kinematics software (Vicon Nexus, Oxford Metrics, UK) derived normalized propulsion and bracing ground reaction force data (Kistler Instrument Corp., Amherst, NY). Post-processing (Visual 3D, C-Motion Inc, Rockville, MD, USA) indicated SFC, MER, and peak linear throwing hand velocity at ball release (BR). RESULTS. Stride lengthening increased propulsion vertical and anterior shear impulses and posterior shear drive foot forces (p<0.001). Greater stride leg posterior shear forces occurred with increased strides (p=0.002). Ball and throwing hand velocities were not affected. DISCUSSION. Overexertion impacting stride length affects baseball pitchers’ typical propulsion and bracing strategies without impacting ball velocity. CONCLUSION. Radar velocities may not detect high effort pitches thrown consistently with altered ground reaction forces, which may lead to arm injuries.
Listed In: Biomechanics, Sports Science