Carbohydrate feeding during prolonged strenuous exercise can delay fatigue

E. F. Coyle, J. M. Hagberg, B. F. Hurley, W. H. Martin, A. A. Ehsani, J. O. Holloszy

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This study was undertaken to determine whether carbohydrate feeding during exercise can delay the development of fatigue. Ten trained cyclists performed two bicycle ergometer exercise tests 1 wk apart. The initial work rate required 74 ± 2% of maximum O2 consumption (V̇O2(max)) (range 70-79% of V̇O2(max)). The point of fatigue was defined as the time at which the exercise intensity the subjects could maintain decreased below their initial work rate by 10% of V̇O2(max). During one exercise test the subjects were fed a glucose polymer solution beginning 20 min after the onset of exercise; during the other they were given a placebo. Blood glucose concentration was 20-40% higher during the exercise after carbohydrate ingestion than during the exercise without carbohydrate feeding. The exercise-induced decrease in plasma insulin was prevented by carbohydrate feeding. The respiratory exchange ratio was unchanged by the glucose feeding. Fatigue was postponed by carbohydrate feeding in 7 of the 10 subjects. This effect appeared to be mediated by prevention of hypoglycemia in only 2 subjects. The exercise time to fatigue for the 10 subjects averaged 134 ± 6 min (mean ± SE) without and 157 ± 5 min with carbohydrate feeding (P < 0.01).

Original languageEnglish
Pages (from-to)230-235
Number of pages6
JournalJournal of Applied Physiology Respiratory Environmental and Exercise Physiology
Issue number1 I
StatePublished - Sep 8 1983


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