Running performance after adaptation to acutely intermittent hypoxia

To quantify the effects of adaptation to acutely intermittent hypoxia on running performance, we randomized 29 trained male hockey and soccer players in double‐blind fashion to altitude or placebo groups for 15 days of daily use of a functional or placebo hypoxic re‐breathing device. Each day's exposure consisted of alternately breathing stale and fresh air for 6 and 4 min respectively over 1 h. Oxygen saturation was monitored with pulse oximeters and progressively reduced in the hypoxia group (90% on Day 1, 77% on Day 15; equivalent to altitudes of ∼3600–6000 m above sea level). Performance tests were an incremental run to maximum speed followed by six maximal‐effort running sprints; tests were performed 1 day before, 3 days after, and 12 days after the 15‐day treatment. Relative to placebo, at 3 days post treatment the hypoxia group showed a mean increase in maximum speed of 2.0% (90% confidence limits, ±0.5%); sprint speed was relatively faster by 1.5% (±1.7%) in the first sprint through 7.0% (±1.5%) in the last; there were also substantial reductions in exercise lactate concentration and resting and exercise heart rate. Substantial effects on performance were still present 9 days later. Thus, adaptation to acutely intermittent hypoxia substantially improves high‐intensity running performance.