Developmental Patterns Of Baseball Performance In Youth Players: A Longitudinal Study

Identifying developmental patterns of baseball-related performance is important to optimize skill acquisition and injury prevention; however, limited studies have examined how baseball performance improves during youth. PURPOSE: (1) To identify developmental patterns in baseball-related performance, including ball speed, swing velocity, and sprint, and (2) to determine their association with growth tempo during youth. METHODS: 962 baseball players aged 6 to 14 years from 15 teams from 2017 to 2022, accounting for up to six testing occasions, participated in this study. Of these, 235 players (557 measurements) who completed two or more measurements were eligible for analysis to evaluate developmental patterns of baseball-related performance (e.g., ball speed in pitching, swing velocity in tee-batting, 30-meter sprint time). The latent growth curve models of the baseball-related performance development process were performed to identify developmental patterns. A subgroup analysis was also conducted to analyze the differences in baseball-related performance development among growth tempo (GT). GT was calculated by the height increase divided by the period from take-off age to peak height velocity age, as analyzed by the AUXAL 3.1 program. Results were classified as gradual (GTG), middle (GTM), and rapid (GTR) by the Z-score. A linear mixed model with baseball-related performance as a fixed effect and individuals as a random effect was used to identify differences in developmental patterns by GT classification. RESULTS: The 30-meter sprint time showed an accelerated improvement at 12–13 years old. However, the ball speed and swing velocity demonstrated a gradual decline and a plateau, respectively, at the same period. GTR had a higher intercept for ball speed (Interact = -0.20, p = 0.008) and swing speed (Interact = -0.12, p = 0.010) than GTG and GTM, whereas the slope was significantly small. CONCLUSION: The development of ball speed and swing speed slows down at age 12-13, and players with rapid GT may be more susceptible to performance stagnation.