title: Reduction in muscle glycogen and protein utilization with glucose feeding during exercise.
abstract: Effects of feeding glucose on substrate metabolism during cycling were studied. Trained (60.0 +/- 1.9 mL x kg(-1) x min(-1)) males (N = 5) completed two 75 min, 80% VO(2max) trials: 125 g 13(C)-glucose CHO); 13(C)-glucose tracer, 10 g (C). During warm-up (30 min 30% VO2max) 2 . 2 g 13(C)-glucose was given as bicarbonate pool primer. Breath samples and blood glucose were analyzed for 13(C/12)C with IRMS. Protein oxidation was estimated from urine and sweat urea. Indirect calorimetry (protein corrected) and 13(C/12)C enrichment in expired CO(2)and blood glucose allowed exogenous (Gexo), endogenous (Gendo), muscle (Gmuscle), and liver glucose oxidation calculations. During exercise (75 min) in CHO versus C (respectively): protein oxidation was lower (6.8 +/- 2.7, 18.8 +/- 5.9 g; P = 0.01); Gendo was reduced (71.2 +/- 3.8, 80.7 +/- 5.7% P = 0.01); Gmuscle was reduced (55.3 +/- 6.1, 65.9 +/- 6.0%; P = 0.01) compensated by increased Gexo(58.3 +/- 2.1, 3.87 +/- 0.85 g; P = 0.000002). Glucose ingestion during exercise can spare endogenous protein and carbohydrate, in fed cyclists, without glycogen depletion.
authors.affiliation: Dept. of Movement Sciences, Maastricht University, Maastricht, The Netherlands.
authors.forename: Dennis
authors.initials: D
authors.lastname: van Hamont
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Harvey
authors.forename: Denis
authors.initials: D
authors.lastname: Massicotte
authors.forename: Russell
authors.initials: R
authors.lastname: Frew
authors.forename: François
authors.initials: F
authors.lastname: Peronnet
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Rehrer
mesh_terms: D000293:Adolescent; D000328:Adult; D001642:Bicycling / Q000502:physiology; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism; D001944:Breath Tests; D002247:Carbon Isotopes; D018592:Cross-Over Studies; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005947:Glucose / Q000493:pharmacokinetics*; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology; D011506:Proteins / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D002247:Carbon Isotopes; D011506:Proteins; D006003:Glycogen; D005947:Glucose