Long-Term Intermittent Hypoxia Increases O 2 -Transport Capacity but Not V O 2max

Abstract

Prommer, Nicole, Katja Heinicke, Teresa Viola, Jorge Cajigal, Claus Behn, and Walter F.J. Schmidt. Long-term intermittent hypoxia increases O₂-transport capacity but not V_O2max . High Alt. Med. Biol. 8:225–235, 2007.—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 V_O2max 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. V_O2max was determined in both groups 1 day after arrival at altitude and at sea level. At altitude, the decrease in V_O2max was less pronounced in IH (10.6 ± 4.2%) than in SL (14.1 ± 4.7%). However, no significant differences in V_O2max were found between the groups either at sea level or at altitude, although arterial oxygen content (Ca_O2 ) 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_O2 mainly resulted from augmented hemoglobin mass (IH: 836 ± 103 g, SL: 751 ± 72g, p < 0.05) and at altitude also from increased arterial O₂-saturation. In conclusion, acclimatization to long-term intermittent hypoxia substantially increases Ca_O2 , but has no beneficial effects on physical performance either at altitude or at sea level.