Document Detail

Evaluation of exercise and training on muscle lipid metabolism.
MedLine Citation:
PMID:  9886956     Owner:  NLM     Status:  MEDLINE    
To evaluate the hypothesis that endurance training increases intramuscular triglyceride (IMTG) oxidation, we studied leg net free fatty acid (FFA) and glycerol exchange during 1 h of cycle ergometry at two intensities before training [45 and 65% of peak rate of oxygen consumption (V(O2) peak)] and after training [65% pretraining V(O2) peak, same absolute workload (ABT), and 65% posttraining V(O2) peak, same relative intensity (RLT)]. Nine male subjects (178.1 +/- 2.5 cm, 81.8 +/- 3.3 kg, 27.4 +/- 2.0 yr) were tested before and after 9 wk of cycle ergometer training, five times per week at 75% V(O2) peak. The power output that elicited 66.1 +/- 1.1% of V(O2) peak before training elicited 54.0 +/- 1.7% after training due to a 14.6 +/- 3.1% increase in V(O2) peak. Training significantly (P < 0.05) decreased pulmonary respiratory exchange ratio (RER) values at ABT (0.96 +/- 0.01 at 65% pre- vs. 0.93 +/- 0.01 posttraining) but not RLT (0.95 +/- 0.01). After training, leg respiratory quotient (RQ) was not significantly different at either ABT (0.98 +/- 0.02 pre- vs. 0.98 +/- 0.03 posttraining) or RLT (1.01 +/- 0.02). Net FFA uptake was increased at RLT but not ABT after training. FFA fractional extraction was not significantly different after training or at any exercise intensity. Net glycerol release, and therefore IMTG lipolysis calculated from three times net glycerol release, did not change from rest to exercise or at ABT but decreased at the same RLT after training. Muscle biopsies revealed minor muscle triglyceride changes during exercise. Simultaneous measurements of leg RQ, net FFA uptake, and glycerol release by working legs indicated no change in leg FFA oxidation, FFA uptake, or IMTG lipolysis during leg cycling exercise that elicits 65% pre- and 54% posttraining V(O2) peak. Training increases working muscle FFA uptake at 65% V(O2) peak, but high RER and RQ values at all work intensities indicate that FFA and IMTG are of secondary importance as fuels in moderate and greater-intensity exercise.
B C Bergman; G E Butterfield; E E Wolfel; G A Casazza; G D Lopaschuk; G A Brooks
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  276     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1999 Jan 
Date Detail:
Created Date:  1999-03-09     Completed Date:  1999-03-09     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  E106-17     Citation Subset:  IM; S    
Department of Integrative Biology, University of California, Berkeley, California 94720, USA.
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MeSH Terms
Blood Glucose / analysis
Calorimetry, Indirect
Carbon Dioxide / blood
Exercise / physiology*
Fatty Acids, Nonesterified / blood,  metabolism
Glycerol / blood
Lactic Acid / blood
Leg / blood supply
Lipid Metabolism*
Muscle, Skeletal / metabolism*
Osmolar Concentration
Oxygen / blood
Physical Education and Training*
Physical Endurance / physiology
Regional Blood Flow / physiology
Triglycerides / metabolism
Grant Support
Reg. No./Substance:
0/Blood Glucose; 0/Fatty Acids, Nonesterified; 0/Triglycerides; 124-38-9/Carbon Dioxide; 50-21-5/Lactic Acid; 56-81-5/Glycerol; 7782-44-7/Oxygen

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