Changes in running endurance performance following intermittent altitude exposure simulated with tents

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The effect of intermittent hypoxia on sea‐level endurance performance was assessed by using hypoxic tents to simulate the live high‐train low approach to altitude training. Eleven male sub‐elite competitive runners and triathletes participated in a crossover study of usual training (control) and usual training with altitude exposure (altitude). Altitude treatment consisted of 25±3 d (mean±SD) of sleeping in tents for 8.1±0.6 h.d −1 , progressing from a simulated altitude of 2500 m to 3500 m above sea level. Washout period between control and altitude treatments was 4 wk. Three treadmill runs to exhaustion lasting ∼2, ∼4 and ∼8 min were completed 7 and 12 d after control and altitude treatments. Times for standard competition distances (800, 1500 and 3000 m), were predicted using a log‐log model, improved by 1.0% (90% confidence limits, ±1.3%), 1.4% (±1.2%) and 1.9% (±1.5%), respectively. Improvements were greater in the six athletes with an I allele for angiotensin converting enzyme (ACE): 2.3% (±1.5%), 2.2% (±1.5%), and 2.1%, (±2.1%), respectively. Effects of simulated altitude on hemoglobin concentration were unclear. Altitude exposure simulated with hypoxic tents is likely to enhance performance substantially in middle‐distance endurance running events, especially for individuals with an I allele of the ACE gene.