ON MAXIMAL OXYGEN-CONSUMPTION IN HYPOXIC HUMANS

The present paper discusses the factors affecting maximal O2 consumption (V(O)2 max) in hypoxia (4300 m above sea level) along the following lines: 1) In acute hypoxia, the fractional limitation to V(O)2 max imposed by circulatory O2 transport (FQ') is 50%, instead of 70% as in normoxia. This is due to the increase in the blood O2 transport coefficient (beta-b) as P(O)2 decreases, as a consequence of the sigmoidal shape of the O2 dissociation curve of hemoglobin. The remaining 50% is assumed to be equally partitioned between tissue O2 transfer (Ft') and mitochondria O2 utilization (Fm'). 2) In chronic hypoxia, FQ' = .045, Ft' = 0.20 and Fm' = 0.35, as a consequence of reduced muscle fiber size and muscle mitochondrial density following acclimatization. 3) The relationship between V(O)2 mas and PI(O)2 in both acute and chronic hypoxia reflects the O2 dissociation curve. 4) Acclimatization to chronic hypoxia does not have the function of preserving V(O)2max.