Training in Normobaric Hypoxia and Its Effects on Acute Mountain Sickness after Rapid Ascent to 4559 m

Abstract

Abstract

Schommer, Kai, Neele Wiesegart, Elmar Menold, Ute Haas, Hermann Buhl, Pezter Bärtsch, and Christoph Dehnert. Training in normobaric hypoxia and its effects on acute mountain sickness after rapid ascent to 4559 m. High Alt. Med. Biol. 11:19–25, 2010.—In a randomized, placebo-controlled, double-blind study, we tested a 4-week program in normobaric hypoxia that is commercially offered for the prevention of acute mountain sickness (AMS). Twenty-two male and 18 female healthy subjects [mean age 33 ± 7 (SD) years] exercised 70 min, 3x/week for 3 weeks on a bicycle ergometer at workloads of 60% Vo₂max either in normoxia (normoxia group, NG) or in normobaric hypoxia (hypoxia group, HG), corresponding to altitudes of 2500, 3000, and 3500 m during weeks 1, 2, and 3, respectively. Four passive exposures of 90 min in normoxia (NG) or hypoxia corresponding to 4500 m (HG) followed in week 4. Five days after the last session, subjects ascended within 24 h from sea level to 4559 m (one overnight stay at 3611 m) and stayed there for 24 h. AMS was defined as LL (Lake Louise score) ≥5 and AMS-C ≥0.70. The AMS incidence (70% in NG vs. 60% in HG, p = 0.74), LL scores (7.1 ± 4.3 vs. 5.9 ± 3.4, p = 0.34), and AMS-C scores (1.50 ± 1.22 vs. 0.93 ± 0.81, p = 0.25) at the study endpoint were not significantly different between the groups. However, the incidence of AMS at 3611 m (6% vs. 47%, p = 0.01) and the functional LL score at 4559 m were lower in HG. Spo₂ at 3611 m, heart rate during ascents, and arterial blood gases at 4559 m were not different between groups. We conclude that the tested program does not reduce the incidence of AMS within a rapid ascent to 4559 m, but our data show that it prevents AMS at lower altitudes. Whether such a program would prevent AMS at higher altitudes, but with slower ascent, remains to be tested.