Effects of Hypoxic Training versus Normoxic Training on Exercise Performance in Competitive Swimmers

In swimming competition, optimal swimming performance is characterized by a variety of interchangeable components, such as aerobic exercise capacity, anaerobic power and muscular function. Various hypoxic training methods would potentiate greater performance improvements compared to similar training at sea-level. Therefore, this study aimed to evaluate the effects of six-weeks of hypoxic training on exercise performance in moderately trained competitive swimmers. Twenty swimmers were equally divided into a normoxic training group (n = 10) for residing and training at sea-level (P_IO₂ = 149.7 mmHg), and a hypoxic training group (n = 10) for residing at sea-level but training at 526 mmHg hypobaric hypoxic condition (P_IO₂ = 100.6 mmHg). Aerobic exercise capacity, anaerobic power, muscular function, hormonal response and 50 and 400 m swimming performance were measured before and after training, which was composed of warm-up, continuous training, interval training, elastic resistance training, and cool-down. The training frequency was 120 min, 3 days per week for 6 weeks. Muscular function and hormonal response parameters showed significant interaction effects (all p < 0.032, η > 0.288) in muscular strength and endurance, growth hormone; GH, insulin like growth factor-1; IGF-1, and vascular endothelial growth factor; VEGF. The other variables demonstrated no significant interaction effects. However, a hypoxic training group also showed significantly increased maximal oxygen consumption; VO₂max (p = 0.001), peak anaerobic power (p = 0.001), and swimming performances for 50 m (p = 0.000) and 400 m (p = 0.000). These results indicated that the hypoxic training method proposed in our study is effective for improvement of muscular strength and endurance in moderately trained competitive swimmers compared to control group. However, our hypoxic training method resulted in unclear changes in aerobic exercise capacity (VO₂max), anaerobic power, and swimming performance of 50 m and 400 m compared to normoxic training.