Abstract
Introduction: Physical preparation is fundamental to school PE, yet heterogeneity exists in the effectiveness of various training models for adolescent fitness, with few empirical comparisons in real educational settings. Objective: This study compared the effects of HIIT, resistance, combined aerobic-resistance, and circuit training on multidimensional physical preparation in secondary school students. Methodology: A 12-week quasi-experimental parallel study included 156 adolescents aged 13–16, cluster-randomized into four intervention groups and one control group (n=39 each). Physical preparation was assessed via cardiorespiratory fitness, strength, endurance, speed-agility and flexibility. Data were analyzed using mixed-design ANOVA, Bonferroni post-hoc tests and effect size calculation. Results: Significant Time × Group interactions were observed across all variables (p < 0.001, η²p = 0.18–0.34). High-intensity interval training produced the largest improvements in cardiorespiratory fitness (ΔVO₂max = +4.2 ml·kg⁻¹·min⁻¹, d = 1.15). Resistance training maximized strength and power development (d = 0.91–0.98). Circuit-based training demonstrated superior muscular endurance (d = 0.96–1.02) and speed-agility improvements (d = 0.87). Combined training generated the most balanced adaptations across domains (mean d = 0.82, SD = 0.09). Post-pubertal participants showed significantly greater strength gains across all models (p < 0.05). Discussion: The findings confirmed distinct domain-specific physiological adaptations across training models, consistent with training specificity literature. Results highlighted the importance of tailored training strategies for targeted physical outcomes in education. Conclusion: Different training models yield specific performance benefits; therefore, schools should implement structured, periodized, and outcome-oriented training programs, with combined and circuit-based approaches offering the most comprehensive physical development.