Document Detail

Fat metabolism during high-intensity exercise in endurance-trained and untrained men.
MedLine Citation:
PMID:  10647075     Owner:  NLM     Status:  MEDLINE    
To determine whether trained individuals rely more on fat than untrained persons during high-intensity exercise, six endurance-trained men and six untrained men were studied during 30 minutes of exercise at 75% to 80% maximal oxygen consumption (VO2max). The rates of appearance (Ra) and disappearance (Rd) of glycerol and free fatty acids (FFAs) were determined using [1,1,2,3,3-2H]glycerol and [1-13C]palmitate, respectively, whereas the overall rate of fatty acid oxidation was determined using indirect calorimetry. During exercise, the whole-body rate of lipolysis (ie, glycerol Ra) was higher in the trained group (7.1 +/- 1.2 v 4.5 +/- 0.7 micromol x min(-1) x kg(-1), P < .05), as was the Ra (approximately Rd) of FFA (9.0 +/- 0.9 v 5.0 +/- 1.0 micromol x min(-1) x kg(-1), P < .001). FFA utilization was higher in trained subjects even when expressed as a percentage of total energy expenditure (10% +/- 1% v 7% +/- 1%, P < .05). However, this difference in plasma FFA flux could not account for all of the difference in fatty acid oxidation between trained and untrained subjects (20.8 +/- 3.3 v 7.9 +/- 1.6 micromol x min(-1) x kg(-1), or 23% +/- 3% v 13% +/- 2% of total energy expenditure, both P < .05). Thus, the oxidation of fatty acids derived from some other source also must have been greater in the trained men. We conclude that trained athletes use more fat than untrained individuals even during intense exercise performed at the same percentage of VO2max. The additional fatty acids appear to be derived from both adipose tissue and, presumably, intramuscular triglyceride stores.
A R Coggan; C A Raguso; A Gastaldelli; L S Sidossis; C W Yeckel
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Metabolism: clinical and experimental     Volume:  49     ISSN:  0026-0495     ISO Abbreviation:  Metab. Clin. Exp.     Publication Date:  2000 Jan 
Date Detail:
Created Date:  2000-02-02     Completed Date:  2000-02-02     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0375267     Medline TA:  Metabolism     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  122-8     Citation Subset:  IM; S    
Shriners Burns Institute and The University of Texas Medical Branch, Galveston, USA.
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MeSH Terms
Epinephrine / blood
Fatty Acids, Nonesterified / blood
Glycerol / blood
Insulin / blood
Lactic Acid / blood
Lipid Metabolism*
Norepinephrine / blood
Physical Endurance / physiology*
Grant Support
Reg. No./Substance:
0/Fatty Acids, Nonesterified; 11061-68-0/Insulin; 50-21-5/Lactic Acid; 51-41-2/Norepinephrine; 51-43-4/Epinephrine; 56-81-5/Glycerol

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