Effect of hyperoxia on aerobic and anaerobic performances and muscle metabolism during maximal cycling exercise
Abstract: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 (W˙max) which was unchanged by hyperoxia; Test 2, an exercise at W˙max (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 W˙max 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 (W˙tot) was determined; W˙tot was elevated by 15% when exercising under hyperoxia; Test 4 (M-Exercise test) consisted also of cycling at W˙max 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.
Document Type: Research Article
Affiliations: 1: Laboratoire de Physiologie – GIP Exercice, Faculté de Médecine Saint-Etienne, 15 rue Ambroise Paré, Saint-Etienne Cedex 2, France 2: Laboratoire Performance Sportive et Santé, Faculté de Sciences et Sports, Av Camille Jullian, Domaine Universitaire, Talence Cedex, France 3: Laboratoire Central de Pharmacologie et de Toxicologie, CHU St-Etienne, Bd Pasteur, Saint-Etienne Cedex, France 4: Laboratoire de Physiologie – GIP Exercice, Faculté de Médecine Lyon-Sud, Oullins Cedex, France
Publication date: 2000-03-01