Physical Performance after Adaptation to Different Protocols of Intermittent Hypoxia

Abstract

PURPOSE: Disparity in reports of the effect of adaptation to acutely intermittent hypoxia on physical performance may be due in part to differences in exposure protocols. Here we report effects of differences in the dose of hypoxia on performance in tests simulating a team sport. METHODS: Fifteen club and junior representative rugby players were randomized to one of four hypoxia dose groups. All players used a personal rebreathing device to achieve 1-hour daily sessions of hypoxia consisting of six intervals of hypoxia interspersed with recovery periods of ambient air. The groups differed in the duration of hypoxia+recovery intervals: 5+5, 6+4, 7+3 and 8+2 min. An initial 15-day loading period of exposures was followed by two 5-day maintenance periods, over a total of 45 d. Pulse oximetry was used to progressively reduce each player's oxygen saturation (Day 1, 89–91%, Day 15 onwards, 76–78%). Before and 2 d after the exposure period, players performed a game-length simulation consisting of 14 circuits, each involving five different sprints and two scrum-like drives. The effect of mean dose of hypoxia (6.5 min; an uncontrolled outcome) and effect of dose difference (1.5 min; effectively a controlled outcome) on sprint speed and drive peak power were expressed as percents, and qualitative inferences were derived by standardizing these effects with pre-exposure standard deviations. RESULTS: The effect of the mean dose was mainly trivial for sprint speeds (−0.6% to 2.3%; 90% confidence limits ±1% to ±2%) but harmful for drive power (−6.2% and −7.2%; ±4.2%). Increasing the dose produced a mixture of trivial, beneficial and harmful differences in sprint speed (−2.6% to 2.4%; ±1.2% to ±2.6%) and an increase in the harmful effect on drive power (by 5.2% and 6.1%; ±4.2%). CONCLUSIONS: There was little consistent effect of intermittent hypoxia on sprint speed, and an apparently harmful effect on drive power would be made worse by increasing the duration of the hypoxic intervals.