| Nutritional strategies to minimize fatigue during prolonged exercise: fluid, electrolyte and energy replacement. | |
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MedLine Citation:
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PMID: 9232556 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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While the presence of palatable (20 mmol l-1) concentrations of NaCl in drinks containing carbohydrate consumed during intense exercise would not be expected to promote absorption or significantly help maintain fluid balance, there is no doubt that athletes should ingest some from of carbohydrate (other than fructose) during moderate-intensity exercise lasting > 90 min. As only approximately 20 g of ingested carbohydrate is oxidized in the first hour of exercise, athletes should probably consume 100 ml every 10 min of a dilute (3-5 g 100 ml-1) carbohydrate solution and thereafter increase the carbohydrate concentration to approximately 10 g 100 ml-1 to match the peak (approximately 1 g min-1) rates of plasma glucose oxidation. Drinking more than those amounts of carbohydrate may increase muscle glycogen oxidation by attenuating the fall in plasma insulin concentration and thereby delaying fat mobilization, especially at relatively low (55% of peak oxygen consumption) intensity exercise. As carbohydrate ingestion does not slow the rate of glycogen utilization in working muscle, it is also advisable for endurance athletes to start exercise with an adequate supply of muscle glycogen, irrespective of whether or not they ingest carbohydrate during exercise. While carbohydrate ingestion 'spares' conversion of liver glycogen to plasma glucose and prevents hypoglycemia, it does not delay the fatigue associated with a low (approximately 20 mmol kg-1) glycogen content in working muscle. Conversely, increases in glycogen content of working muscle at the start of exercise have no effect on the rates of plasma glucose oxidation. Higher initial rates of glycogen utilization by active muscles in 'carbohydrate-loaded' subjects decrease the indirect oxidation (via lactate) of non-working muscle glycogen, rather than the conversion of liver glycogen to plasma glucose. Hence, athletes should ingest carbohydrate during endurance exercise even if they have 'carbohydrate-loaded' before exercise. |
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Authors:
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S C Dennis; T D Noakes; J A Hawley |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Journal of sports sciences Volume: 15 ISSN: 0264-0414 ISO Abbreviation: J Sports Sci Publication Date: 1997 Jun |
Date Detail:
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Created Date: 1997-09-09 Completed Date: 1997-09-09 Revised Date: 2007-11-15 |
Medline Journal Info:
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Nlm Unique ID: 8405364 Medline TA: J Sports Sci Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 305-13 Citation Subset: IM; S |
Affiliation:
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MRC/UCT Bioenergetics of Exercise Research Unit, University of Cape Town Medical School, Sports Science, Institute of South Africa, Newlands, South Africa. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Dietary Carbohydrates
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administration & dosage* Electrolytes / administration & dosage Energy Intake* Exercise / physiology* Fatigue / prevention & control* Fluid Therapy* Glycogen / metabolism Guidelines as Topic Humans Muscle, Skeletal / physiology Water-Electrolyte Balance / physiology* |
| Chemical | |
Reg. No./Substance:
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0/Dietary Carbohydrates; 0/Electrolytes; 9005-79-2/Glycogen |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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