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 (CaO2 ) 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 CaO2 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 CaO2 , but has no beneficial effects on physical performance either at altitude or at sea level.
© Copyright 2007 High Altitude Medicine & Biology. Mary Ann Liebert. Alle Rechte vorbehalten.