Effect of hyperoxia on aerobic and anaerobic performances and muscle metabolism during maximal cycling exercise.
The hyperoxia-improved tolerance to maximal aerobic performance was studied in relation to exercising muscle metabolic state. Five students were submitted to four different tests on a cycle ergometer, each being conducted under normoxia and hyperoxia (60% FiO2) on separate days: Test 1, a progressive exercise until exhaustion to determine the maximal work load (Wmax) which was unchanged by hyperoxia; Test 2, an exercise at Wmax (287 +/- 12 W) until exhaustion to determine the performance time (texh) which was elevated by 38% under hyperoxia but exhaustion occurred at the same arterial proton and lactate concentrations; Test 3 (S-Exercise test) consisted of cycling at Wmax for 90% normoxic-texh (4.8 +/- 0.5 min under both O2 conditions) then followed by a 10-s sprint bout during which the total work output (Wtot) was determined; Wtot was elevated by 15% when exercising under hyperoxia; Test 4 (M-Exercise test) consisted also of cycling at Wmax for 4.8 +/- 0.5 min with blood and muscle samples taken at rest and at the end of the exercise to compare the level of different metabolites. During hyperoxic M-Exercise test, glycogen was twice more depleted whereas glucose-6-phosphate and lactate were less accumulated when compared with normoxia. No significant differences were observed for pyruvate, phosphocreatine and muscle/blood lactate ratio between the two conditions. Conversely to normoxia, levels of ATP, ADP and total NADH were maintained at their resting level under 60% FiO2. These data lead us to suppose a higher oxidation rate for pyruvate and NADH in mitochondria, thereby lowering the metabolic acidosis and allowing a better functioning of the glycolytic and contractile processes to delay the time to exhaustion.
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Laboratoire de Physiologie - GIP Exercice, Faculté de Médecine Saint-Etienne, 15 rue Ambroise Paré, Saint-Etienne Cedex 2, France.
Dormois
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Arsac
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Denis
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Gay
J P
JP
Geyssant
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Lacour
J R
JR
D000328:Adult; D000332:Aerobiosis; D000693:Anaerobiosis; D001769:Blood / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006019:Glycolysis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018496:Hyperoxia / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology
D019344:Lactic Acid