The Effects of Plyometric Training on Basic and Specialized Physical Fitness in Elite Middle School Baseball Players

Purpose: This study examined the effects of a 12-week plyometric training program on basic physical fitness and sport-specific fitness in elite middle school baseball players. Methods: Twenty-four elite middle school baseball players participated in a single-group pre–post design. The plyometric training program was periodized into three phases: adaptation (weeks 1–4), power development (weeks 5–8), and sport-specific conversion/peaking (weeks 9–12), with progressive overload based on RPE and ground contacts. Basic physical fitness variables included back strength, sit-ups, standing long jump, side step, light reaction time, trunk lift, sit-and-reach, and one-leg stance. Sport-specific fitness variables included anaerobic power (mean power and peak power) and eye–hand coordination (time and errors). Paired t-tests were conducted with the significance level set at p<.05. Results: Back strength, sit-ups, standing long jump, and side step significantly improved after training (all p<.001). Light reaction time decreased but was not statistically significant ( p>.05). Flexibility (trunk lift, sit-and-reach) and balance (one-leg stance) showed no significant changes ( p>.05). For sport-specific fitness, mean power and peak power significantly increased (both p<.001). Eye–hand coordination time significantly decreased ( p<.01), whereas coordination errors showed a non-significant decreasing trend ( p>.05). Conclusion: A 12-week periodized plyometric training program improved key components of basic physical fitness (strength, muscular endurance, power, and agility) and sport-specific fitness (anaerobic power and coordination time) in elite middle school baseball players. These findings support the practical use of progressive, phase-based plyometric training to enhance performance-related fitness in adolescent baseball athletes.