Long-term intermittent hypoxia increases O2-transport capacity but not VO2max

High Alt Med Biol. Fall 2007;8(3):225-35. doi: 10.1089/ham.2007.8309.


Long-term intermittent hypoxia, characterized by several days or weeks at altitude with periodic stays at sea level, is a frequently occurring pattern of life in mountainous countries demanding a good state of physical performance. The aim of the study was to determine the effects of a typical South American type of long-term intermittent hypoxia on VO2max at altitude and at sea level. We therefore compared an intermittently exposed group of soldiers (IH) who regularly (6 months) performed hypoxic-normoxic cycles of 11 days at 3550 m and 3 days at sea level with a group of soldiers from sea level (SL, control group) at 0 m and in acute hypoxia at 3550 m. VO2max was determined in both groups 1 day after arrival at altitude and at sea level. At altitude, the decrease in VO2max was less pronounced in IH (10.6 +/- 4.2%) than in SL (14.1 +/- 4.7%). However, no significant differences in VO2max were found between the groups either at sea level or at altitude, although arterial oxygen content (Ca(O(2) )) at maximum exercise was elevated (p < 0.001) in IH compared to SL by 11.7% at sea level and by 8.9% at altitude. This higher Ca(O(2) ) mainly resulted from augmented hemoglobin mass (IH: 836 +/- 103 g, SL: 751 +/- 72 g, p < 0.05) and at altitude also from increased arterial O(2)-saturation. In conclusion, acclimatization to long-term intermittent hypoxia substantially increases Ca(O(2) ), but has no beneficial effects on physical performance either at altitude or at sea level.

Publication types

  • Clinical Trial
  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological
  • Adult
  • Altitude Sickness / blood*
  • Altitude*
  • Analysis of Variance
  • Blood Volume
  • Chile
  • Erythrocyte Count
  • Erythrocyte Volume
  • Erythropoietin / blood
  • Hemoglobins / analysis
  • Humans
  • Hypoxia / blood*
  • Male
  • Military Personnel*
  • Oxygen Consumption


  • Hemoglobins
  • Erythropoietin