Document Detail

Muscle metabolic, SR Ca(2+) -cycling responses to prolonged cycling, with and without glucose supplementation.
MedLine Citation:
PMID:  17916667     Owner:  NLM     Status:  MEDLINE    
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.
T A Duhamel; H J Green; R D Stewart; K P Foley; I C Smith; J Ouyang
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Publication Detail:
Type:  Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't     Date:  2007-10-04
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  103     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2007 Dec 
Date Detail:
Created Date:  2007-12-06     Completed Date:  2008-02-21     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1986-98     Citation Subset:  IM    
Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada.
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MeSH Terms
Administration, Oral
Blood Glucose / drug effects,  metabolism
Calcium / metabolism*
Drug Administration Schedule
Energy Metabolism / drug effects
Glucose / administration & dosage,  pharmacology*
Glycogen / metabolism
Lactic Acid / blood
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
Reg. No./Substance:
0/Blood Glucose; 50-21-5/Lactic Acid; 50-99-7/Glucose; 7440-70-2/Calcium; 9005-79-2/Glycogen; EC Reticulum Calcium-Transporting ATPases

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