title: Carbohydrate feeding during prolonged strenuous exercise can delay fatigue.
abstract: 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).
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004837:Epinephrine / Q000097:blood; D005080:Exercise Test; D005221:Fatigue; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005947:Glucose / Q000008:administration & dosage; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D007003:Hypoglycemia / Q000517:prevention & control; D007328:Insulin / Q000097:blood; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D009132:Muscles / Q000378:metabolism* / Q000502:physiology; D010807:Physical Endurance; D005082:Physical Exertion; D011659:Pulmonary Gas Exchange; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D007773:Lactates; D019344:Lactic Acid; D006003:Glycogen; D005947:Glucose; D004837:Epinephrine