Effects of high-intensity interval repeated sprint training with change of direction on aerobic and anaerobic capacity in 16-year-old male soccer players

Background: High-Intensity Interval Training (HIIT) with Repeated Sprint Training (RST) and Change of Direction (COD) is a promising approach to enhance aerobic and anaerobic capacities in youth soccer players, particularly in non-elite settings where resources are limited. However, its efficacy in improving soccer-specific physiological outcomes remains underexplored in non-elite U-17 populations. Aim: This study aimed to evaluate the effects of an 8-week HIIT RST program with COD on aerobic (VO2max, YYIR1 running distance) and anaerobic (RAST anaerobic capacity) capacities in non-elite 16-year-old male soccer players. Methods: Sixteen male soccer players (age: 16 ± 0.5 years) underwent an 8-week HIIT RST program (2 sessions/week, 10s maximal sprints, 45°/90° COD, 1:5 work-to-rest ratio). Pre- and post-intervention assessments included the Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) for VO2max and running distance, and the Running-based Anaerobic Sprint Test (RAST) for anaerobic capacity (sum of six sprint PPOs). Paired t-tests assessed within-group changes, with Cohen’s d effect sizes (small: 0.2, medium: 0.5, large: 0.8) and significance set at p