The study investigated the ingestion of maltodextrin, fructose, and protein on exogenous carbohydrate oxidation (CHOEXO) and exercise performance. Seven trained cyclists and (or) triathletes (maximal oxygen consumption, 59.20 ± 9.00 mL/kg/min) performed 3 exercise trials that consisted of 150 min of cycling at 50% maximal power output (160 ± 11 W), followed by a 60-km time trial. One of 3 beverages were randomly assigned during each trial and consumed at 15-min intervals: (i) 0.84 g/min maltodextrin + 0.52 g/min fructose + 0.34 g/min protein (MD+F+P); (ii) 1.10 g/min maltodextrin + 0.60 g/min fructose (MD+F); or (iii) 1.70 g/min maltodextrin (MD). CHOEXO and fuel utilisation were assessed via measurement of expired air 13C content and indirect calorimetry, respectively. Mean total CHO oxidation (CHOTOT) rates were 2.35 ± 0.18, 2.76 ± 0.08, and 2.61 ± 0.17 g/min with MD, MD+F, and MD+F+P, respectively, although not significantly different. Peak CHOEXO rates with MD+F were significantly greater by 41.4% (p = 0.001) and 45.4% (p = 0.0001) compared with MD+F+P and MD, respectively (1.57 ± 0.22 g/min, 1.11 ± 0.08 g/min, and 1.08 ± 0.11 g/min, respectively). Performance times were 2.2% and 5.0% faster with MD+F compared with MD+F+P and MD, respectively; however, they were not statistically significant. Ingestion of an MD-fructose-protein commercial sports beverage significantly reduced peak and mean CHOEXO rates compared with MD+F, but did not significantly influence CHOTOT. The addition of protein to an MD+F beverage did not enhance performance times.
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