Effects of intermittent hypoxic exposure on physical performance in trained basketball players
Strong evidence exists to support the use of a continuous (>8hr/day) hypoxic stimulus (either geographical altitude or simulated hypoxia) for enhancing the physical performance of endurance athletes. However, evidence supporting the use of acutely intermittent hypoxia (<1hr/day) for enhancing performance is less clear. The purpose of this study was to determine the effect of acutely intermittent hypoxic exposure on physiological and physical performance measures in team sport athletes. Using a single-blind controlled design, 14 trained basketball players (HYP = 7, CON = 7) were subjected to 15 days of intermittent hypoxia or normoxia. Each exposure was 37 minutes in duration (four cycles of 7min on, 3min off) and achieved using a nitrogen dilution device (Airo Ltd, Auckland, NZ). Prescribed peripheral oxygen saturation levels (SpO2) were maintained using an automatic biofeedback system and were progressively decreased from 86-89% on Day 1 to 75-78% on Day 15. A range of physiological measures and performance tests were conducted seven and two days before, and ten days after the intervention. The tests were: an incremental treadmill test to establish peak oxygen consumption ( peak) and running economy (RE), Yo-Yo Intermittent Recovery Test (YYIRT), and the Repeated High-Intensity Endurance Test (RHIET). Whole-blood samples were taken to assess a range of haematological measures. At 10 days post-intervention the HYP group, relative to the CON group, exhibited the following percent changes (±90% confidence limits, CL), and effect sizes (ES; ±90% CL); YYIRT running speedpeak (4.8; ± 1.6%, ES: 1.0 ± 0.4; benefit almost certain), RHIET total sprint time (-3.5; ± 1.6%; ES: -0.4 ± 0.2; benefit very likely), RHIET slowest sprint time (-5.0; ± 2.4%; ES: -0.5 ± 0.2; benefit very likely), soluble transferrin receptor (9.2; ± 10.1%; ES: 0.3 ± 0.3; benefit possible) running economy (11km.hr-1) (-9.0; ± 9.7%; ES: -0.7 ± 0.7; benefit likely, probable), and running economy (13km.hr-1) (-8.2; ± 6.9%; ES: -0.7 ± 0.5; benefit likely, probable). Changes to running economy (9km.hr-1), peak, maximum heart rate and lactate and all other blood measures were unclear. In conclusion, acutely intermittent hypoxia resulted in worthwhile changes in physical performance of trained basketball players in tests relevant to competition. However, the lack of clear change in physiological and haematological measures makes it difficult to determine the underlying mechanism for such enhancement.