title: Oxidation rates of orally ingested carbohydrates during prolonged exercise in men.
abstract: Six male volunteers exercised on a cycle ergometer at 65% of maximal work load for 120 min on six occasions while ingesting water (W) only, four doses of maltodextrin (M) [0.92, 1.85, 2.77, and 3.70 g/kg body wt (4, 8, 12, and 16% M, respectively)], and sucrose (S) [1.85 g/kg body wt (8% S)]. Drinks were given during warm-up (8 ml/kg body wt) and each 15 min during exercise (2 ml/kg body wt). M and S were of high 13C natural abundance. Total carbohydrate (CHO) and fat oxidations were calculated from the nonprotein respiratory exchange ratio. M and S increased total CHO oxidation compared with W; no difference was observed between CHO solutions. Total CHO oxidation decreased continuously with time and more rapidly after W than after M or S. Fat oxidation increased continuously in all treatments. Oxidation rates of ingested CHO were 52 +/- 19, 76 +/- 12, 86 +/- 10, and 91 +/- 9 g/2 h for 4, 8, 12, and 16% M, respectively. The oxidation rate of S was 81 +/- 10 g/2 h (not different from 8% M), which indicated that the glucose polymer had no advantage over S. Oxidation rates of M and S increased to a plateau after 90-120 min of exercise. For all solutions except 4% M, the plateau oxidation rate was close to 1.0 g/min. Differences between 8, 12, and 16% M and 8% S were minimal such that ingestion of 8% M or S may well have had an optimal ergogenic effect.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Human Biology, University of Limburg, Maastricht, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: Wagenmakers
authors.forename: F
authors.initials: F
authors.lastname: Brouns
authors.forename: W H
authors.initials: WH
authors.lastname: Saris
authors.forename: D
authors.initials: D
authors.lastname: Halliday
mesh_terms: D000328:Adult; D001642:Bicycling; D002151:Calorimetry; D002245:Carbon Dioxide / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000493:pharmacokinetics*; D004041:Dietary Fats / Q000493:pharmacokinetics; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology; D011134:Polysaccharides / Q000493:pharmacokinetics; D013395:Sucrose / Q000493:pharmacokinetics
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D011134:Polysaccharides; D002245:Carbon Dioxide; D013395:Sucrose; C008315:maltodextrin