Effects of a 12-week extracurricular resistance training program on physical fitness parameters in adolescents: a controlled quasi-experimental study

Background and Study Aim. Physical activity during adolescence is essential not only for healthy growth but also for maintaining mental balance and recovery from everyday stress. In India, many schools lack structured recreational fitness programs, which limits opportunities for students to engage in health-oriented activity. Resistance training, while often considered a performance method, may also function as a tool for recreation and rehabilitation. The aim of this study was to evaluate the effects of a 12-week structured resistance training program on physical fitness and to examine its recreational and rehabilitative relevance for adolescents aged 13–16 years. Materials and Methods. Ninety-nine students (IG = 50; CG = 49) from two public schools in North Delhi participated. The intervention group undertook three weekly 60-minute resistance training sessions for 12 weeks, while the control group continued regular school activities. Outcomes included muscular endurance, power, speed, aerobic capacity, balance, coordination, flexibility, and BMI. A 2×2 mixed MANOVA tested Group × Time effects, followed by repeated-measures ANOVAs and paired t-tests. Effect sizes were reported using η² and Cohen’s d. Results. Significant Group × Time interactions were observed for muscular endurance and power, including sit-ups (η² = 0.23, p < 0.001), push-ups (η² = 0.19, p < 0.001), and broad jump (η² = 0.26, p < 0.001). Speed improved significantly in the 20-m sprint (η² = 0.14, p < 0.001). Within the intervention group, large effect sizes were found for sit-ups (d = 1.20), push-ups (d = 1.07), and broad jump (d = 1.35). Moderate gains were detected in countermovement jump, aerobic capacity, lateral jumps, and balance. Flexibility and BMI did not change, confirming that adaptations were domain-specific. Conclusions. A structured 12-week resistance training program proved safe, feasible, and effective in enhancing strength, power, speed, and endurance among adolescents. Beyond physiological outcomes, the program demonstrated recreational and rehabilitative value by providing a supportive context for recovery, stress reduction, and long-term engagement in active lifestyles. These findings support the integration of resistance training into school-based physical education as a model for recreation- and rehabilitation-oriented practice.