Assessment of Muscular Fatigue on Hip and Torso Biomechanics in Adolescent Baseball Pitchers

Johnson, AL, Kokott, W, Dziuk, C, and Cross, JA. Assessment of muscular fatigue on hip and torso biomechanics in adolescent baseball pitchers. J Strength Cond Res 39(8): 893-899, 2025-Muscular fatigue is an injury risk indicator, and its effect on pitching biomechanics warrants investigation. This study evaluated hip and torso biomechanics to measure muscular fatigue after a limited number of pitches thrown. We hypothesized that postpitching tests would reveal reduced stride length and hip and torso strength, altering hip and torso kinematics and increasing throwing arm kinetics. Adolescent male baseball pitchers' hip and abdominal oblique strength were measured before and after a short pitching session. Pitching biomechanics were calculated from pitches within the first 5 and last 5 of a single throwing session. Means and standard deviations were calculated, and a linear regression model examined the relationships between total number of pitches and dependent variables, with significance level of p ≤ 0.05. Seventeen adolescent male baseball pitchers (age: 17.1 ± 1.0 years, height: 183.9 ± 7.1 cm, mass: 82.9 ± 10.3 kg) completed an average 35 pitches. Significant decreases were found for torso rotation angle and body separation angle at ball release, along with decreased timing of maximum shoulder internal rotation velocity. Strength measurements significantly decreased for back hip extension, lead hip extension, back hip external rotation, lead hip external rotation, and lead hip internal rotation. The linear regression model showed 3 significant observations: body separation angle at foot contact, body separation angle at ball release, and peak pelvis rotation velocity. Scatter plots demonstrated a bimodal distribution between 35 and 40 pitches, with more variability at higher pitch counts. Significant changes in pre- and postpitching tests highlight the impact of muscular fatigue, demonstrating areas for targeted strength training in adolescent baseball pitchers.