Document Detail

Preexercise muscle glycogen content affects metabolism during exercise despite maintenance of hyperglycemia.
MedLine Citation:
PMID:  9458751     Owner:  NLM     Status:  MEDLINE    
Trained cyclists with low muscle glycogen (LGH; n = 8) or normal glycogen (NGH; n = 5) exercised for 145 min at 70% of maximal oxygen uptake during a hyperglycemic clamp. Respiratory exchange ratio was higher in NGH than LGH, and free fatty acid concentrations were lower in NGH than LGH. Areas under the curve for insulin and lactate were lower in LGH than NGH. Total glucose infusion and total glucose oxidation were not different between NGH and LGH, and total glucose oxidation amounted to 65 and 66% of total glucose infusion in NGH and LGH, respectively. Rates of glucose oxidation rose during exercise, reaching peaks of 9.2 +/- 1.7 and 8.3 +/- 1.1 mmol/min in NGH and LGH, respectively. Muscle glycogen disappearance was greater in NGH than LGH. Thus 1) low muscle glycogen content does not cause increased glucose oxidation, even during hyperglycemia; instead there is an increase in fat oxidation, 2) there is an upper limit to the rate of glucose oxidation during exercise with hyperglycemia irrespective of muscle glycogen status, and 3) net muscle glycogen utilization is determined by muscle glycogen content at the start of exercise, even during hyperglycemia.
S M Weltan; A N Bosch; S C Dennis; T D Noakes
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of physiology     Volume:  274     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1998 Jan 
Date Detail:
Created Date:  1998-02-19     Completed Date:  1998-02-19     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  E83-8     Citation Subset:  IM; S    
Department of Physiology, University of Cape Town Medical School, Observatory, South Africa.
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MeSH Terms
Analysis of Variance
Blood Glucose / metabolism
Fatty Acids, Nonesterified / blood
Glucagon / blood
Glucose Clamp Technique
Glycogen / metabolism*
Hyperglycemia / physiopathology*
Lactates / blood
Muscle Fatigue
Muscle, Skeletal / physiology*
Oxygen Consumption*
Physical Endurance / physiology*
Physical Exertion / physiology*
Reg. No./Substance:
0/Blood Glucose; 0/Fatty Acids, Nonesterified; 0/Lactates; 9005-79-2/Glycogen; 9007-92-5/Glucagon

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