Effects of high-intensity interval training under hypoxic conditions on energy system performance in collegiate football players

Introduction: High-Intensity Interval Training (HIIT) is widely recognized for enhancing athletic performance. However, whether simulated hypoxic conditions amplify the physiological effects of HIIT especially in sports like football that rely on multiple energy systems, remains underexplored. Objective: To investigate whether simulated hypoxic HIIT elicits greater improvements in aerobic and anaerobic performance compared to normoxic HIIT and standard training in collegiate football players. Methodology: Twenty-four male collegiate football players were randomly assigned to three groups: Hypoxic HIIT, Normoxic HIIT, or Control. Over a four-week intervention period, the experimental groups engaged in sport-specific HIIT under their respective environmental conditions, while all participants continued standard team training. Pre- and post-training assessments included VO₂max, Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1), Running-Based Anaerobic Sprint Test (RAST), and 30-meter flying sprint. Results: The Hypoxic HIIT group showed significant improvements in VO₂max and Yo-Yo IR1 distance (p < 0.01), with moderate gains in RAST peak power. Minimal changes were observed in ATP-PC system performance. These adaptations exceeded those observed in the Normoxic and Control groups. Discussion: The findings indicate that hypoxic stress provides an additive stimulus to aerobic conditioning. This aligns with existing literature on the role of hypoxia in enhancing oxygen transport, mitochondrial function, and endurance capacity. Conclusions: Simulated hypoxic HIIT effectively enhances aerobic capacity and selectively improves anaerobic performance. It represents a time-efficient and evidence-based conditioning strategy for competitive football.