High Oxidation Rates from Combined Carbohydrates Ingested during Exercise


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Abstract

JENTJENS, R. L. P. G., J. ACHTEN, and A. E. JEUKENDRUP. High Oxidation Rates from Combined Carbohydrates Ingested during Exercise. Med. Sci. Sports Exerc., Vol. 36, No. 9, pp. 1551–1558, 2004. Studies that have investigated oxidation of a single carbohydrate (CHO) during exercise have reported oxidation rates of up to 1 g·min−1. Recent studies from our laboratory have shown that a mixture of glucose and sucrose or glucose and fructose ingested at a high rate (1.8 g·min−1) leads to peak oxidation rates of ~1.3 g·min−1 and results in ~20 to 55% higher exogenous CHO oxidation rates compared with the ingestion of an isocaloric amount of glucose.Purpose:The purpose of the present study was to examine whether a mixture of glucose, sucrose and fructose ingested at a high rate would result in even higher exogenous CHO oxidation rates (>1.3 g·min−1).Methods:Eight trained male cyclists (V̇O2max: 64 ±·kg−1 BM·min−1) cycled on three different occasions for 150 min at 62 ± 1% V̇O2max and consumed either water (WAT) or a CHO solution providing 2.4 g·min−1 of glucose (GLU) or 1.2 g·min−1 of glucose + 0.6 g·min−1 of fructose + 0.6 g·min−1 of sucrose (MIX).Results:High peak exogenous CHO oxidation rates were found in the MIX trial (1.70 ± 0.07 g·min−1), which were ~44% higher (P < 0.01) compared with the GLU trial (1.18 ± 0.04 g·min−1). Endogenous CHO oxidation was lower (P < 0.05) in MIX compared with GLU (0.76 ± 0.12 and 1.05 ± 0.06 g·min−1, respectively).Conclusion:When glucose, fructose and sucrose are ingested simultaneously at high rates (2.4 g·min−1) during cycling exercise, exogenous CHO oxidation rates can reach peak values of ~1.7 g·min−1 and estimated endogenous CHO oxidation is reduced compared with the ingestion of an isocaloric amount of glucose.

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