Assessing a commercially available sports drink on exogenous carbohydrate oxidation, fluid delivery and sustained exercise performance

Background: Whilst exogenous carbohydrate oxidation (CHOEXO) is influenced by mono-and disaccharide combinations, debate exists whether such beverages enhance fluid delivery and exercise performance. Therefore, this study aimed to ascertain CHOEXO, fluid delivery and performance times of a commercially available maltodextrin/fructose beverage in comparison to an isocaloric maltodextrin beverage and placebo. Methods: Fourteen club level cyclists (age: 31.79 +/- 10.02 years; height: 1.79 +/- 0.06 m; weight: 73.69 +/- 9.24 kg; VO2max: 60.38 +/- 9.36 mL.kg(-1) min(-1)) performed three trials involving 2.5 hours continuous exercise at 50% maximum power output (W-max: 176.71 +/- 25.92 W) followed by a 60 km cycling performance test. Throughout each trial, athletes were randomly assigned, in a double-blind manner, either: (1) 1.1 g.min(-1) maltodextrin + 0.6 g.min(-1) fructose (MD + F), (2) 1.7 g.min(-1) of maltodextrin (MD) or (3) flavoured water (P). In addition, the test beverage at 60 minutes contained 5.0 g of deuterium oxide ((H2O)-H-2) to assess quantification of fluid delivery. Expired air samples were analysed for CHOEXO according to the C-13/C-12 ratio method using gas chromatography continuous flow isotope ratio mass spectrometry. Results: Peak CHOEXO was significantly greater in the final 30 minutes of submaximal exercise with MD + F and MD compared to P (1.45 +/- 0.09 g.min(-1), 1.07 +/- 0.03 g.min(-1) and 0.00 +/- 0.01 g.min(-1) respectively, P < 0.0001), and significantly greater for MD + F compared to MD (P = 0.005). The overall appearance of (H2O)-H-2 in plasma was significantly greater in both P and MD + F compared to MD (100.27 +/- 3.57 ppm, 92.57 +/- 2.94 ppm and 78.18 +/- 4.07 ppm respectively, P < 0.003). There was no significant difference in fluid delivery between P and MD + F (P = 0.078). Performance times significantly improved with MD + F compared with both MD (by 7 min 22 s +/- 1 min 56 s, or 7.2%) and P (by 6 min 35 s +/- 2 min 33 s, or 6.5%, P < 0.05) over 60 km. Conclusions: A commercially available maltodextrin-fructose beverage improves CHOEXO and fluid delivery, which may benefit individuals during sustained moderate intensity exercise. The greater CHOEXO observed when consuming a maltodextrin-fructose beverage may support improved performance times.