Training in normobaric hypoxia and its effects on acute mountain sickness after rapid ascent to 4559 m

High Alt Med Biol. Spring 2010;11(1):19-25. doi: 10.1089/ham.2009.1019.

Abstract

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, 3 x /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) > or =5 and AMS-C > or =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.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Acclimatization*
  • Adult
  • Altitude Sickness / epidemiology
  • Altitude Sickness / prevention & control*
  • Blood Gas Analysis
  • Double-Blind Method
  • Female
  • Heart Rate
  • Hematocrit
  • Hemoglobins / analysis
  • Humans
  • Hypoxia*
  • Lactic Acid / blood
  • Male
  • Oximetry
  • Physical Education and Training / methods*

Substances

  • Hemoglobins
  • Lactic Acid