Effects of HIIT long interval training-based running with change of direction on aerobic and anaerobic capacity of youth soccer players

Background: Soccer demands robust aerobic and anaerobic capacities to sustain high-intensity running, sprinting, and change of direction (COD) actions, particularly for youth players developing competitive fitness. Enhancing these capacities in-season is critical for performance and progression in amateur settings. Aim: This study investigated the effects of an 8-week high-intensity interval training (HIIT) protocol with COD on aerobic (Yo-Yo Intermittent Recovery Test Level 1 [YYIR1]) and anaerobic (Running-based Anaerobic Sprint Test [RAST]) capacities in U-17 male soccer players. Methods: Twenty-five male players (age: 16.0±0.5 years) from the “Albanët” Football Team, Albanian Football Federation, participated. Pre- and post-intervention assessments included anthropometric measurements (height, weight, BMI), YYIR1 (VO2max, distance), and RAST (anaerobic capacity: sum of six sprint peak power outputs [PPOs]). The 8-week intervention (2 sessions/week, 70 s at 105% maximal aerobic speed, 1:5 work-to-rest ratio, 840 m/session) incorporated 45° and 90° COD on a FIFA-standard artificial pitch. Paired-sample t-tests assessed changes (p