Exogenous carbohydrate oxidation from drinks ingested during prolonged exercise in a cold environment in humans

S. D. Galloway, S. A. Wootton, Joanne Murphy, Ronald John Maughan

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    Six healthy male volunteers performed four rides to exhaustion on a cycle ergometer at similar to 80% of maximal oxygen consumption. Subjects ingested a bolus volume of fluid (7.14 ml/kg) immediately before exercise and additional fluid volumes (1.43 ml/kg) every 10 min during exercise. The fluids ingested were either a flavored water control or glucose- electrolyte beverages with glucose concentrations of 2, 6, or 12%. The beverages were labeled with [U-C-13] glucose (99.2%: 0.05 g/l). Exercise capacity was not different (P = 0.13) between trials; median (range) exercise time was 83.52 (79.85-89.68), 103.19 (78.82-108.22), 100.37 (80.60-124.07), and 94.76 (76.78-114.25) min in the 0, 2, 6, and 12% trials, respectively. The oxidation of exogenous glucose in each 15-min period was significantly lower in the 2% trial (P = 0.02) than in the 6 and 12% trials where oxidation rates were between 0.5 and 0.7 g/min. No difference in endogenous glucose oxidation was observed between trials (P = 0.71). These findings indicate that the oxidation of exogenous glucose during exercise of this intensity and duration in a cold environment is similar to that observed in warmer conditions. Thus a low oxidation of exogenous substrate is unlikely to be a factor limiting the effectiveness of carbohydrate-electrolyte drink ingestion on exercise capacity in a cold environment.

    Original languageEnglish
    Pages (from-to)654-660
    Number of pages6
    JournalJournal of Applied Physiology
    Issue number2
    Publication statusPublished - 2001


    • stable isotopes
    • hydration
    • glucose oxidation
    • PLASMA
    • BLOOD
    • MEN


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