Effect of hyperoxia on metabolic and catecholamine responses to prolonged exercise

Abstract

The use of inspired gas mixtures with an oxygen fraction in excess of 0.3 has been associated with a decrease in the gas exchange ratio (R) during prolonged work in humans. It had been hypothesized that the lower R was due to a lower plasma catecholamine concentration caused by the hyperoxia (Med. Sci. Sports 10: 167-170, 1978). We tested this hypothesis by measuring changes in plasma epinephrine and norepinephrine when the subjects were switched from breathing air to 60% O2 (and vice versa) during 40 min of cycle ergometer exercise at 67% maximal oxygen uptake (VO2max). The subject breathed one gas mixture for the first 30 min and was switched to the other in the last 10 min. The order was reversed in the second test. The switch in gas mixtures from air to 60% O2 resulted in a significant reduction in R, heart rate, minute ventilation, blood lactate concentration, and plasma epinephrine concentration (P less than 0.05). The plasma norepinephrine concentration (0.1 greater than P greater than 0.05) and the plasma free fatty acid concentration were not significantly changed. Although the direction of the epinephrine change was consistent with the change in R, the epinephrine change was quantitatively small (20 pg/ml) and of questionable physiological significance. This suggests a direct effect of PO2 on cellular metabolism as one cause of the change in R when the subjects were switched from air to 60% O2.

Effect of exercise-induced arterial hypoxemia on quadriceps muscle fatigue in healthy humans

“…The slight but significant increase in V O 2 ( (14,20,23,32) and to increase locomotor muscle V O 2 (28).…”

Effects of moderate hyperoxia on oxygen consumption during submaximal and maximal exercise

“…Some authors have reported no significant difference in _ V V O 2 during submaximal exercise (Adams and Welch 1980;Byrnes et al 1984;Welch and Pedersen 1981), while three studies found an increase in _ V V O 2 under hyperoxia (Graham and Wilson 1983;Hogan and Welch 1984;Howley et al 1983). In spite of these contradictory results, it has been suggested that the body's metabolic response changes during exercise under hyperoxia (Howley et al 1983;Welch and Pedersen 1981).…”

A high blood lactate induced by heavy exercise does not affect the increase in submaximal $$\dot V{\text{O}}_2 $$ with hyperoxia

“…As we conducted this operation in the two ambiances, there should be no methodological bias relative to this technique in one condition compared to the other. Besides, several studies with different measurement techniques such as Douglas bags (Wilson et al 1975), automatic systems (Prieur et al 2002), mixing chamber (Howley et al 1983) or different analysers such as micro-Scholander apparatus (Wilson et al 1975;Howley et al 1983), mass spectrometer (Peltonen et al 2001b), electrochemical (Prieur et al 2002) or paramagnetic analyzers (present study) evidenced a rise of _ V O 2 in hyperoxia. On the other hand, it has been shown (Hornby et al 1995) that infrared analyser underestimates F E CO 2 when not using hyperoxic calibration gases (e.g.…”

“…The only greater oxidation of fatty acids during hyperoxia proposed by several authors appears here to be insufficient to explain the whole _ V O 2 excess. Moreover, studies from Howley et al (1983), Adams et al (1986) and Linossier et al (2000) concluded that blood levels of free fatty acids were similar and that there was no glycogen sparing during exercise in hyperoxia. Thus, there should be another mechanism responsible for the O 2 overconsumption in hyperoxia.…”

“…At maximal exercise, this is illustrated by the larger increase in maximal oxygen uptake _ V O 2 max À Á than in maximal work rate (WR max ): on average 11-12% versus 3-4%, respectively (Peltonen et al 1995(Peltonen et al , 2001a(Peltonen et al , 2001bNielsen et al 1998Nielsen et al , 1999Prieur et al 2002;Wilber et al 2003). Moreover, several studies evidenced an increase in oxygen uptake _ V O 2 À Á during submaximal exercise in hyperoxia than in normoxia, at the same absolute WR (Wilson et al 1975;Graham and Wilson 1983;Howley et al 1983;Prieur et al 1998Prieur et al , 2002Peltonen et al 2001b). However, occurrence of O 2 overconsumption with hyperoxia for moderate intensity exercises, i.e.…”