EFFECTS OF A 12-WEEK HIGH-INTENSITY INTERVAL TRAINING VERSUS MODERATE-INTENSITY CONTINUOUS TRAINING PROGRAMME ON AEROBIC CAPACITY AND BODY COMPOSITION IN MIXED-SEX UNIVERSITY ATHLETES: A RANDOMIZED CONTROLLED TRIAL

Authors: Karimov Bekzod Boyqobilovich

Abstract: Background: High-Intensity Interval Training (HIIT) has emerged as a time-efficient alternative to Moderate-Intensity Continuous Training (MICT) for improving cardiorespiratory fitness and body composition. However, comparative evidence among mixed-sex university athlete populations using extended 12-week protocols remains limited. Objective: This randomized controlled trial aimed to compare the effects of 12-week HIIT and MICT programmes on maximal oxygen uptake (VO₂max), body composition, and resting heart rate in university athletes. Methods: Thirty university athletes (n = 18 males, n = 12 females; mean age 21.4 ± 2.1 years) were randomly allocated to either a HIIT group (n = 15) or a MICT group (n = 15). The HIIT protocol consisted of 4 × 4-minute intervals at 85–95% of maximum heart rate (HRmax) with 3-minute active recovery periods, performed three sessions per week. The MICT protocol involved continuous treadmill running at 60–70% HRmax for 40 minutes, three sessions per week. Primary outcomes — VO₂max (20-metre multistage fitness test), body fat percentage (bioelectrical impedance analysis), and resting heart rate — were assessed at baseline and post-intervention. Statistical analyses included paired-samples t-tests, independent-samples t-tests, two-way repeated-measures ANOVA, Cohen's d effect sizes, and 95% confidence intervals. Results: Both groups demonstrated significant within-group improvements across all outcomes (p < 0.05). The HIIT group showed significantly greater improvements in VO₂max (Δ = 4.8 mL·kg⁻¹·min⁻¹; d = 1.14; p = 0.003) and body fat percentage (Δ = −3.2%; d = 0.98; p = 0.007) compared to the MICT group. No significant between-group difference was found for resting heart rate (p = 0.21). Conclusion: Twelve weeks of HIIT produced superior aerobic capacity and body composition improvements compared to isocaloric-matched MICT in university athletes. HIIT represents a time-efficient, evidence-based training modality suitable for integration into university physical education curricula.

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