Longitudinal Trajectories of Basic and Sport-Specific Fitness in High-School Water Polo Athletes

During adolescence, athletes undergo concurrent biological maturation and training-induced adaptation, making the transition from general to sport-specific fitness a critical phase in performance development. This longitudinal study investigated changes in basal and sport-specific fitness over three years in high school male water polo athletes. Ten athletes were assessed annually for basal fitness (e.g., sit-up, vertical jump, back strength, shuttle run, and flexibility) and for proxy sport-specific indicators, including isokinetic strength and anaerobic power. Repeated-measures ANCOVA (controlling for height and weight) and multiple regression analyses were conducted to evaluate temporal changes and inter-variable associations. Significant improvements were observed in vertical jump and back strength, whereas isokinetic strength and anaerobic power remained statistically unchanged. However, the notable rise from Year 1 to Year 2 followed by stabilization suggested a potential critical window for the transition of general to sport-specific capacities. Regression models demonstrated moderate explanatory power, although individual predictors were not statistically significant. These findings indicate that explosive lower-limb power and posterior chain strength develop selectively during this developmental period, supporting the nonlinear and maturation-dependent nature of fitness adaptation. Practically, early-to-mid high school may represent an optimal stage for integrating foundational strength programs with water-specific performance training.