title: Assessing a commercially available sports drink on exogenous carbohydrate oxidation, fluid delivery and sustained exercise performance.
abstract: 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 (Wmax: 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 (2H2O) to assess quantification of fluid delivery. Expired air samples were analysed for CHOEXO according to the 13C/12C 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-1and 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 2H2O 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.
authors.affiliation: School of Life & Medical Sciences, University of Hertfordshire, College Lane, Hatfield, Hertfordshire, UK.
authors.forename: Justin D
authors.initials: JD
authors.lastname: Roberts
authors.affiliation: School of Life & Medical Sciences, University of Hertfordshire, College Lane, Hatfield, Hertfordshire, UK.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Tarpey
authors.affiliation: School of Life & Medical Sciences, University of Hertfordshire, College Lane, Hatfield, Hertfordshire, UK.
authors.forename: Lindsy S
authors.initials: LS
authors.lastname: Kass
authors.affiliation: School of Life & Medical Sciences, University of Hertfordshire, College Lane, Hatfield, Hertfordshire, UK.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Tarpey
authors.affiliation: School of Life & Medical Sciences, University of Hertfordshire, College Lane, Hatfield, Hertfordshire, UK.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Roberts