Associations Between Lower Limb Stiffness and Baseball Pitching and Batting Velocity are Influenced by Playing Level and Body Mass

Previous research shows a positive relationship between countermovement jump (CMJ) stiffness and baseball pitching velocity, suggesting that athletes who exhibit greater spring-like lower limb mechanics may generate greater throwing speeds. However, it remains unclear whether this relationship persists for batting or if these relationships remain consistent across playing levels. PURPOSE: The purpose of this study was to examine the relationship between CMJ-derived lower limb stiffness and both pitching and batting velocity across high school (HS), collegiate (COL), and professional (PRO) baseball players. METHODS: HS, COL, and PRO baseball players performed countermovement jumps using dual force plates (1000 Hz). Lower limb stiffness was calculated as peak eccentric phase force divided by countermovement displacement. Peak pitching and batting velocity were measured using camera-based motion capture (360 Hz). Data were extracted from the OpenBiomechanics Project (Wasserberger et al. 2022), and included 911 pitchers (317 HS, 470 COL, 124 PRO) and 1069 batters (549 HS, 437 COL, 83 PRO). Pearson correlations were used to examine relationships between stiffness and velocity metrics within each playing level. Partial correlations were additionally calculated to control for body mass. RESULTS: Significant small-to-moderate correlations were observed between absolute lower limb stiffness and bat velocity (HS r=0.50, p