| Muscle metabolic, SR Ca(2+) -cycling responses to prolonged cycling, with and without glucose supplementation. | |
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MedLine Citation:
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PMID: 17916667 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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This study investigated the effects of prolonged exercise, with and without glucose supplementation, on metabolism and sarcoplasmic reticulum (SR) Ca(2+)-handling properties in working vastus lateralis muscle. Fifteen untrained volunteers [peak O(2) consumption (Vo(2peak)) = 3.45 +/- 0.17 l/min; mean +/- SE] cycled at approximately 60% Vo(2peak) on two occasions, during which they were provided with either an artificially sweetened placebo beverage (NG) or a 6% glucose (G) beverage (~1.00 g carbohydrate/kg body mass). Beverage supplementation started at 30 min of exercise and continued every 15 min thereafter. SR Ca(2+) handling, metabolic, and substrate responses were assessed in tissue extracted from the vastus lateralis at rest, after 30 min and 90 min of exercise, and at fatigue in both conditions. Plasma glucose during G was 15-23% higher (P < 0.05) than those observed during NG following 60 min of exercise until fatigue. Cycle time to fatigue was increased (P < 0.05) by approximately 19% during G (137 +/- 7 min) compared with NG (115 +/- 6 min). Prolonged exercise reduced (P < 0.05) maximal Ca(2+)-ATPase activity (-18.4%), SR Ca(2+) uptake (-27%), and both Phase 1 (-22.2%) and Phase 2 (-34.2%) Ca(2+)-release rates during NG. The exercise-induced reductions in SR Ca(2+)-cycling properties were not altered during G. The metabolic responses to exercise were all unaltered by glucose supplementation, since no differences in respiratory exchange ratios, carbohydrate and lipid oxidation rates, and muscle metabolite and glycogen contents were observed between NG and G. These results indicate that the maintenance of blood glucose homeostasis by glucose supplementation is without effect in modifying the muscle metabolic, endogenous glycogen, or SR Ca(2+)-handling responses. |
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Authors:
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T A Duhamel; H J Green; R D Stewart; K P Foley; I C Smith; J Ouyang |
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Publication Detail:
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Type: Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't Date: 2007-10-04 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 103 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2007 Dec |
Date Detail:
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Created Date: 2007-12-06 Completed Date: 2008-02-21 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: United States |
Other Details:
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Languages: eng Pagination: 1986-98 Citation Subset: IM |
Affiliation:
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Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Administration, Oral Adult Beverages* Bicycling* Blood Glucose / drug effects, metabolism Calcium / metabolism* Drug Administration Schedule Energy Metabolism / drug effects Female Glucose / administration & dosage, pharmacology* Glycogen / metabolism Humans Lactic Acid / blood Male Muscle Contraction / drug effects* Muscle Fatigue / drug effects Muscle, Skeletal / drug effects*, enzymology, metabolism Oxygen Consumption / drug effects Physical Exertion / physiology* Respiration / drug effects Sarcoplasmic Reticulum / drug effects*, enzymology, metabolism Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism Time Factors |
| Chemical | |
Reg. No./Substance:
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0/Blood Glucose; 50-21-5/Lactic Acid; 50-99-7/Glucose; 7440-70-2/Calcium; 9005-79-2/Glycogen; EC 3.6.3.8/Sarcoplasmic Reticulum Calcium-Transporting ATPases |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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