Carbohydrate feeding during prolonged strenuous exercise can delay fatigue

J Appl Physiol Respir Environ Exerc Physiol. 1983 Jul;55(1 Pt 1):230-5. doi: 10.1152/jappl.1983.55.1.230.


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 (VO2 max) (range 70-79% of VO2 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 VO2 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 two 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 less than 0.01).

Publication types

  • Clinical Trial
  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Blood Glucose / metabolism
  • Dietary Carbohydrates / administration & dosage*
  • Epinephrine / blood
  • Exercise Test
  • Fatigue*
  • Fatty Acids, Nonesterified / blood
  • Female
  • Glucose / administration & dosage
  • Glycogen / metabolism*
  • Humans
  • Hypoglycemia / prevention & control
  • Insulin / blood
  • Lactates / blood
  • Lactic Acid
  • Male
  • Muscles / metabolism*
  • Muscles / physiology
  • Physical Endurance*
  • Physical Exertion*
  • Pulmonary Gas Exchange
  • Time Factors


  • Blood Glucose
  • Dietary Carbohydrates
  • Fatty Acids, Nonesterified
  • Insulin
  • Lactates
  • Lactic Acid
  • Glycogen
  • Glucose
  • Epinephrine