In this novel study of effects of acutely intermittent simulated altitude exposure on running performance, 29 highly trained male soccer and hockey players were each randomly allocated a functional or placebo re-breathing device for 15 d. Each day`s exposure consisted of alternately breathing hypoxic and ambient air for 6 and 4 min respectively over 1 h. Oxygen saturation was monitored individually with pulse oximeters and progressively reduced in the altitude group (Day 1, 90%; Day 15, 77%). Performance tests, which included blood-lactate and heart-rate measurements, were an incremental run to peak speed followed by six maximal-effort sprints; tests were performed 1 d before, 3 d after, and 12 d after the 15-d treatment. Blood-cell counts were taken 1 d pre and post treatment. Measures of blood acid-base status were taken immediately pre and post exposure on Days 1 and 15. Relative to placebo, at 3 d post treatment the altitude group showed a mean increase in peak speed of 2.0% (90% confidence limits, ±0.5%); sprint speed was also relatively faster by 1.5% in the first sprint through 6.9% in the last (±1.9%). Noteworthy changes in blood measures in the altitude group relative to placebo were increases in hemoglobin concentration (1.2%, ±1.9%) and hematocrit (2.0%, ±2.7%) and substantial reductions in exercise lactates and resting and exercise heart rates. Large effects on performance were still present 9 d later. We conclude that acutely intermittent simulated altitude exposure dramatically improves high-intensity running performance possibly via changes in oxygen transport rather than buffering capacity.
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