Changes in Running Performance Following Intermittent Altitude Exposure Simulated With Tents

Abstract

Exposure to natural altitude using the live high-train low method enhances endurance performance at sea level, but the effect of exposure to simulated altitude is less clear. PURPOSE To investigate the effect of intermittent hypoxia on sea-level performance by simulating altitude with hypoxic tents. METHODS Eleven male competitive runners and triathletes (age 31 ± 9 y, mean ± standard deviation) 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 hr per day, progressing from a simulated altitude of 2500 m to 3500 m above sea level. Washout period between control and altitude treatments was 4 wk. Performance tests, scheduled 7 d after the control and altitude treatments, were three treadmill runs to exhaustion lasting ± 2, ± 4 and ± 8 min. Some athletes repeated the tests 5 d later. Times for standard competitions distances (800, 1500 and 3000 m) were predicted using a log-log model and analyzed by mixed modeling. Venous blood was sampled at 4 wk and 1 wk before and 1–7 d after altitude and control treatments RESULTS Effects of altitude exposure on predicted 800, 1500 and 3000 m performance were enhancements of 1.0% (90% confidence limits, ± 1.3%), 1.4% (± 1.2%) and 1.8% (± 1.5%) respectively. Enhancements were greater in the six athletes carrying an I allele for angiotensin converting enzyme (ACE): 2.3% (± 1.4%), 2.2% (± 1.4%), and 2.1%, (± 2.2%) respectively. For a smallest substantial change in performance of 0.5%, chances of real benefit were likely (>75%) and chances of real harm were very unlikely (<5%) for all these effects. The effects were apparently unrelated to oxygen carrying capacity of the blood, which showed a trend towards a decrease in mean values for hemoglobin concentration and hematocrit following the altitude treatment relative to the control. CONCLUSIONS The effects of altitude exposure on endurance performance after the use of hypoxic tents are worthwhile, but only for elite athletes. If further research supports the effects of the ACE genotype on performance, genotype assessment would make use of tents more cost effective.