Abstract des Autors

In order to determine the level of hypoxemia which is sufficient to impair maximal performance, seven well-trained male cyclists <maximum oxygen consumption (VO2max) >/= 5 l/min or 60 ml/kg/min> performed a 5-min performance cycle test to exhaustion at maximal intensity as controlled by the subject, under three experimental conditions: normoxemia (persentage of arterial oxyhemoglobin saturation (SaO2) > 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, undere normoxemia, mild, and moderate hypoxemia, respectively>. However, only performance in the moderate hypoxemia condition was significanlty different than in normoxemia (P=0.02). Mean oxygen consumption and heart rate were similar in the three conditions (P=0.18 and P=0.95, respectively). End-tidal partial pressure of CO2 was significantly lower (P=0.005) during moderate hypoxemia compared with normoxemia, and ventilatroy 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.