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Failure of hypoxia to exaggerate the metabolic stress in working muscle following short-term training

Department of Kinesiology, University of Waterloo, Ontario, Canada

Submitted 19 December 2008 ; accepted in final form 23 May 2009

This study investigated the effects of hypoxia (experiment 1) and the effects of hypoxia following short-term training (experiment 2) on metabolism in working muscle. In experiment 1, eight males with a peak aerobic power (O_2peak) of 45 ± 1.7 ml·kg^–1·min^–1 ( ± SE) cycled for 15 min at 66.1 ± 2.1% O_2peak while breathing room air [normoxia (N)] or 14% O₂ [hypoxia (H)]. In experiment 2, nine males with a O_2peak of 43.3 ± 1.6 ml·kg^–1·min^–1 performed a similar protocol at 60.7 ± 1.4% O_2peak during N and during H following 5 days of submaximal exercise training (H + T). Tissue samples extracted from the vastus lateralis before exercise and at 1, 3, and 15 min of exercise indicated that compared with N, H resulted in lower (P < 0.05) concentrations (mmol/kg dry wt) of creatine phosphate and higher (P < 0.05) concentrations of creatine, inorganic phosphate, and lactate, regardless of exercise time. When the exercise was performed at H + T and compared with N, no differences were observed in creatine phosphate, creatine, inorganic phosphate, and lactate, regardless of duration. Given the well-documented effects of the short-term training model on elevating O₂ kinetics and attenuating the alterations in high-energy phosphate metabolism and lactate accumulation, it would appear that the mechanism underlying the reversal of these adaptations during H is linked to a more rapid increase in oxidative phosphorylation, mediated by increased oxygen delivery and/or mitochondrial activation.

metabolism; regular exercise; nonsteady state

This article has been cited by other articles:

				H. J. Green, E. Bombardier, M. E. Burnett, I. C. Smith, S. M. Tupling, and D. A. Ranney Time-dependent effects of short-term training on muscle metabolism during the early phase of exercise Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2009; 297(5): R1383 - R1391. [Abstract] [Full Text] [PDF]