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This Article Full Text Full Text (PDF) All Versions of this Article: 297/5/R1383    most recent 00203.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Green, H. J. Articles by Ranney, D. A. PubMed PubMed Citation Articles by Green, H. J. Articles by Ranney, D. A.

Articles

Time-dependent effects of short-term training on muscle metabolism during the early phase of exercise

Department of Kinesiology, University of Waterloo, Waterloo, Ontarion, Canada

Submitted April 9, 2009 ; accepted in final form August 17, 2009

In this study, we investigated the hypothesis that the metabolic adaptations observed during steady-state exercise soon after the onset of training would be displayed during the nonsteady period of moderate exercise and would occur in the absence of increases in peak aerobic power (o_2peak) and in muscle oxidative potential. Nine untrained males [age = 20.8 ± 0.70 (SE) yr] performed a cycle task at 62% o_2peak before (Pre-T) and after (Post-T) training for 2 h/day for 5 days at task intensity. Tissue samples extracted from the vastus lateralis at 0 min (before exercise) and at 10, 60, and 180 s of exercise, indicated that at Pre-T, reductions (P < 0.05) in phosphocreatine and increases (P < 0.05) in creatine, inorganic phosphate, calculated free ADP, and free AMP occurred at 60 and 180 s but not at 10 s. At Post-T, the concentrations of all metabolites were blunted (P < 0.05) at 60 s. Training also reduced (P < 0.05) the increase in lactate and the lactate-to-pyruvate ratio observed during exercise at Pre-T. These adaptations occurred in the absence of change in o_2peak (47.8 ± 1.7 vs. 49.2 ± 1.7 ml·kg^–1·min^–1) and in the activities (mol·kg protein^–1·h^–1) of succinic dehydrogenase (3.48 ± 0.21 vs. 3.77 ± 0.35) and citrate synthase (7.48 ± 0.61 vs. 8.52 ± 0.65) but not cytochrome oxidase (70.8 ± 5.1 vs. 79.6 ± 6.6 U/g protein; P < 0.05). It is concluded that the tighter metabolic control observed following short-term training is initially expressed during the nonsteady state, probably as a result of increases in oxidative phosphorylation that is not dependent on changes in o_2peak while the role of oxidative potential remains uncertain.

adaptation; exercise; muscle; non-steady state; metabolism; enzymes