title: Effects of 7 wk of endurance training on human skeletal muscle metabolism during submaximal exercise.
abstract: This is the first study to examine the effects of endurance training on the activation state of glycogen phosphorylase (Phos) and pyruvate dehydrogenase (PDH) in human skeletal muscle during exercise. We hypothesized that 7 wk of endurance training (Tr) would result in a posttransformationally regulated decrease in flux through Phos and an attenuated activation of PDH during exercise due to alterations in key allosteric modulators of these important enzymes. Eight healthy men (22 +/- 1 yr) cycled to exhaustion at the same absolute workload (206 +/- 5 W; approximately 80% of initial maximal oxygen uptake) before and after Tr. Muscle biopsies (vastus lateralis) were obtained at rest and after 5 and 15 min of exercise. Fifteen minutes of exercise post-Tr resulted in an attenuated activation of PDH (pre-Tr: 3.75 +/- 0.48 vs. post-Tr: 2.65 +/- 0.38 mmol.min(-1).kg wet wt(-1)), possibly due in part to lower pyruvate content (pre-Tr: 0.94 +/- 0.14 vs. post-Tr: 0.46 +/- 0.03 mmol/kg dry wt). The decreased pyruvate availability during exercise post-Tr may be due to a decreased muscle glycogenolytic rate (pre-Tr: 13.22 +/- 1.01 vs. post-Tr: 7.36 +/- 1.26 mmol.min(-1).kg dry wt(-1)). Decreased glycogenolysis was likely mediated, in part, by posttransformational regulation of Phos, as evidenced by smaller net increases in calculated muscle free ADP (pre-Tr: 111 +/- 16 vs. post-Tr: 84 +/- 10 micromol/kg dry wt) and P(i) (pre-Tr: 57.1 +/- 7.9 vs. post-Tr: 28.6 +/- 5.6 mmol/kg dry wt). We have demonstrated for the first time that several signals act to coordinately regulate Phos and PDH, and thus carbohydrate metabolism, in human skeletal muscle after 7 wk of endurance training.
authors.affiliation: Department of Medicine, McMaster University Health Science Centre, Hamilton, ON, Canada L8N 3Z5.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Leblanc
authors.forename: Krista R
authors.initials: KR
authors.lastname: Howarth
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Gibala
authors.forename: George J F
authors.initials: GJ
authors.lastname: Heigenhauser
mesh_terms: D000108:Acetylcarnitine / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006003:Glycogen / Q000378:metabolism; D024981:Glycogen Phosphorylase / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D010725:Phosphocreatine / Q000378:metabolism; D010807:Physical Endurance / Q000502:physiology*; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism; D019289:Pyruvic Acid / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D011768:Pyruvate Dehydrogenase Complex; D010725:Phosphocreatine; D019344:Lactic Acid; D000108:Acetylcarnitine; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D006003:Glycogen; D024981:Glycogen Phosphorylase