Optimising adolescent health: a comparative study of high-intensity interval training and moderate-intensity continuous training on body composition and cardiovascular fitness in sedentary male youth.

BACKGROUND

Excess body fat and weight are key risk factors for morbidity and mortality, particularly during adolescence. High-Intensity Interval Training (HIIT) and Moderate-Intensity Continuous Training (MICT) are both widely used strategies to improve body composition, yet limited evidence exists comparing their effects among sedentary, normal-weight adolescent males.

METHODS

This randomized controlled study aimed to compare the effects of HIIT and MICT on body composition and cardiovascular fitness in sedentary male adolescents. Sixty normal-weight males aged 16-17 years were randomly assigned to one of three groups: HIIT (n = 20), MICT (n = 20), or control (CG; n = 20). The HIIT protocol comprised six 30-second high-intensity running intervals (80%-90% HRmax) interspersed with 90 s of low-intensity walking (50% HRmax), totalling 20 min per session. The MICT protocol involved continuous running at 60%-70% HRmax for 30 min, inclusive of warm-up and cool-down. Both intervention groups trained four times weekly over 8 weeks, while the control group received no intervention. Pre- and post-intervention measurements included body fat percentage, body weight, skinfold thickness, and resting heart rate, analysed using one-way ANOVA with Bonferroni post hoc comparisons. Given its shorter duration and comparable outcomes, HIIT appears time-efficient for school-based delivery in normal-weight adolescent males, addressing a population and setting under-represented in prior trials.

RESULTS

Significant reductions in body fat were observed in both the HIIT (-6.0%, p < 0.001, ES = 0.97) and MICT (-5.7%, p < 0.001, ES = 0.76) groups, with no meaningful change in the CG (-1.0%, p > 0.05). Both HIIT and MICT groups also demonstrated significant weight loss (-7.45%, p < 0.001), compared to a negligible change in CG (-0.89%, p > 0.05). Skinfold thickness significantly decreased in HIIT (-24.70%, p < 0.001) and MICT (-23.66%, p < 0.001), with minor change in CG (-4.12%, p > 0.05). Resting heart rate improved in HIIT (-9.14%, p < 0.001) and MICT (-7.12%, p < 0.001), whereas the CG experienced a slight increase (+0.026%, p > 0.05).

CONCLUSIONS

Both HIIT and MICT are effective for improving body composition and cardiorespiratory fitness in sedentary male adolescents. Given its shorter duration and comparable outcomes, HIIT may be a time-efficient option for integration into school-based physical education.