Arterial hypoxemia and performance during intense exercise
- Cite this article as:
- Koskolou, M.D. & McKenzie, D.C. Europ. J. Appl. Physiol. (1994) 68: 80. doi:10.1007/BF00599246
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In order to determine the level of hypoxemia which is sufficient to impair maximal performance, seven well-trained male cyclists [maximum oxygen consumption (VO2max)≥51·min−1 or 60 ml·kg−1·min−1] performed a 5-min performance cycle test to exhaustion at maximal intensity as controlled by the subject, under three experimental conditions: normoxemia [percentage of arterial oxyhemoglobin saturation (%Sa O2)>94%], and artificially induced mild (%SaO2=90±1%) and moderate (%SaO2=87±1%) hypoxemia. Performance, evaluated as the total work output (Worktot) performed in the 5-min cycle test, progressively decreased with decreasing %SaO2 [mean (SE) Worktot=107.40 (4.5) kJ, 104.07 (5.6) kJ, and 102.52 (4.7) kJ, under normoxemia, mild, and moderate hypoxemia, respectively]. However, only performance in the moderate hypoxemia condition was significantly different than in normoxemia (P=0.02). Mean oxygen consumption and heart rate were similar in the three conditions (P=0.18 andP=0.95, respectively). End-tidal partial pressure of CO2 was significantly lower (P=0.005) during moderate hypoxemia compared with normoxemia, and ventilatory equivalent of CO2 was significantly higher (P=0.005) in both hypoxemic conditions when compared with normoxemia. It is concluded that maximal performance capacity is significantly impaired in highly trained cyclists working under an %SaO2 level of 87% but not under a milder desaturation level of 90%.