title: Human muscle metabolism during intermittent maximal exercise.
abstract: Eight male subjects volunteered to take part in this study. The exercise protocol consisted of ten 6-s maximal sprints with 30 s of recovery between each sprint on a cycle ergometer. Needle biopsy samples were taken from the vastus lateralis muscle before and after the first sprint and 10 s before and immediately after the tenth sprint. The energy required to sustain the high mean power output (MPO) that was generated over the first 6-s sprint (870.0 +/- 159.2 W) was provided by an equal contribution from phosphocreatine (PCr) degradation and anaerobic glycolysis. Indeed, within the first 6-s bout of maximal exercise PCr concentration had fallen by 57% and muscle lactate concentration had increased to 28.6 mmol/kg dry wt, confirming significant glycolytic activity. However, in the tenth sprint there was no change in muscle lactate concentration even though MPO was reduced only to 73% of that generated in the first sprint. This reduced glycogenolysis occurred despite the high plasma epinephrine concentration of 5.1 +/- 1.5 nmol/l after sprint 9. In face of a considerable reduction in the contribution of anaerobic glycogenolysis to ATP production, it was suggested that, during the last sprint, power output was supported by energy that was mainly derived from PCr degradation and an increased aerobic metabolism.
authors.affiliation: Department of Physical Education, Sports Science, and Recreation Management, Loughborough University, Leicestershire, United Kingdom.
authors.forename: G C
authors.initials: GC
authors.lastname: Gaitanos
authors.forename: C
authors.initials: C
authors.lastname: Williams
authors.forename: L H
authors.initials: LH
authors.lastname: Boobis
authors.forename: S
authors.initials: S
authors.lastname: Brooks
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001810:Blood Volume / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D004837:Epinephrine / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D009132:Muscles / Q000378:metabolism*; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D010725:Phosphocreatine / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D007773:Lactates; D010725:Phosphocreatine; D019344:Lactic Acid; D000255:Adenosine Triphosphate; D006003:Glycogen; D009638:Norepinephrine; D004837:Epinephrine