Document Detail

Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling.
MedLine Citation:
PMID:  20466803     Owner:  NLM     Status:  MEDLINE    
We determined the effects of varying daily carbohydrate intake by providing or withholding carbohydrate during daily training on endurance performance, whole body rates of substrate oxidation, and selected mitochondrial enzymes. Sixteen endurance-trained cyclists or triathletes were pair matched and randomly allocated to either a high-carbohydrate group (High group; n = 8) or an energy-matched low-carbohydrate group (Low group; n = 8) for 28 days. Immediately before study commencement and during the final 5 days, subjects undertook a 5-day test block in which they completed an exercise trial consisting of a 100 min of steady-state cycling (100SS) followed by a 7-kJ/kg time trial on two occasions separated by 72 h. In a counterbalanced design, subjects consumed either water (water trial) or a 10% glucose solution (glucose trial) throughout the exercise trial. A muscle biopsy was taken from the vastus lateralis muscle on day 1 of the first test block, and rates of substrate oxidation were determined throughout 100SS. Training induced a marked increase in maximal citrate synthase activity after the intervention in the High group (27 vs. 34 micromol x g(-1) x min(-1), P < 0.001). Tracer-derived estimates of exogenous glucose oxidation during 100SS in the glucose trial increased from 54.6 to 63.6 g (P < 0.01) in the High group with no change in the Low group. Cycling performance improved by approximately 6% after training. We conclude that altering total daily carbohydrate intake by providing or withholding carbohydrate during daily training in trained athletes results in differences in selected metabolic adaptations to exercise, including the oxidation of exogenous carbohydrate. However, these metabolic changes do not alter the training-induced magnitude of increase in exercise performance.
Gregory R Cox; Sally A Clark; Amanda J Cox; Shona L Halson; Mark Hargreaves; John A Hawley; Nikki Jeacocke; Rodney J Snow; Wee Kian Yeo; Louise M Burke
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Publication Detail:
Type:  Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't     Date:  2010-05-13
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  109     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2010 Jul 
Date Detail:
Created Date:  2010-06-30     Completed Date:  2010-10-14     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:  126-34     Citation Subset:  IM    
Sports Nutrition, Australian Institute of Sport, Queensland Academy of Sport, PO Box 956, Nathan, Queensland 4111, Australia.
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MeSH Terms
Adaptation, Physiological
Citrate (si)-Synthase / analysis
Dietary Carbohydrates / administration & dosage,  metabolism*
Energy Metabolism
Exercise / physiology*
Exercise Test
Glucose / administration & dosage,  metabolism*
Glycogen / analysis,  metabolism
Muscle, Skeletal / cytology,  physiology
Physical Endurance / physiology*
Young Adult
Reg. No./Substance:
0/Dietary Carbohydrates; 50-99-7/Glucose; 9005-79-2/Glycogen; EC (si)-Synthase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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