title: Glycogen reduction in non-exercising muscle depends on blood lactate concentration.
abstract: The purpose of this study was to determine for the first time by repeated non-invasive 13C-NMR spectrometry whether blood lactate concentration affects glycogen reduction in non-exercising muscle during prolonged (6 h) physical exercise in healthy adult males. Such an effect would indirectly show that glycogenolysis independent of nervous activation occurs in non-exercising muscle. After an overnight fast, 12 subjects performed alternating one-leg cycle exercise and arm cranking exercise at an average work load of 106 (SD 26) W [63 (9)% maximum oxygen consumption for one-leg exercise] and 69 (13) W [61 (10)% maximum oxygen consumption for arm cranking exercise], respectively. During the 6-h exercise test, glycogen concentration of the non-exercising calf muscle decreased by 17 (7)% while the glycogen concentration in the exercising calf muscle decreased by 45 (8)%. In a resting control group (n=6), the glycogen concentration did not decrease significantly. The higher the exercise intensity and therefore blood lactate concentration, the smaller was the glycogen reduction in the non-exercising calf muscles. We conclude that during prolonged physical exercise glycogenolysis in non-exercising human muscles decreases as exercise intensity increase contrary to exercising muscles. This observation might be an indirect evidence for a non-exercise induced glycogenolysis in inactive muscles.
authors.affiliation: Exercise Physiology, Institute for Human Movement Sciences, Swiss Federal Institute of Technology, Winterthurerstr. 190, 8057 Zurich, Switzerland. kohlerg@physiol.unizh.ch
authors.forename: Götz
authors.initials: G
authors.lastname: Kohler
authors.forename: Urs
authors.initials: U
authors.lastname: Boutellier
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism; D004576:Electromyography; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D005260:Female; D006003:Glycogen / Q000097:blood / Q000378:metabolism*; D006801:Humans; D019344:Lactic Acid / Q000097:blood*; D007866:Leg / Q000502:physiology; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D012146:Rest / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D019344:Lactic Acid; D006003:Glycogen