Intermittent hypoxic training (IHT) is sometimes used by athletes to enhance non-hematological physiological adaptations to simulated altitude. This study investigated whether IHT would result in greater improvements in muscle energetics and exercise tolerance compared with work matched intermittent normoxic (sea level) training (INT).

Physically active men (n=9) completed 3 weeks of intensive, single-leg knee-extensor exercise training. Each training session consisted of 25 min of Intermittent Hypoxic Training with the experimental leg and 25 min of Intermittent Normoxic Training withthe alternate leg, which served as a control.

Before and after the training intervention, subjects completed a test protocol consisting of a bout of submaximal constant-work-rate exercise, a 24-s high-intensity exercise bout to quantify the phosphocreatine recovery time constant, and an incremental test to the limit of tolerance.The tests were completed in normoxia and hypoxia in both INT and IHT legs.

Improvements in the time-to-exhaustion during incremental exercise were not significantly different between training conditions either in normoxia or hypoxia. Changes in muscle metabolite concentrations during exercise were essentially not different between Intermittent Hypoxic Training and Intermittent Normoxic Training. Under the conditions of this investigation, IHT does not appreciably alter muscle metabolic responses or incremental exercise performance compared with INT.