title: Self-selecting fluid intake while maintaining high carbohydrate availability does not impair half-marathon performance.
abstract: We aimed to test the hypothesis that self-selecting fluid intake but maintaining high exogenous CHO availability (60 g/h) does not compromise half-marathon performance. 15 participants completed 3 half-marathons while drinking a 6% CHO solution to guidelines (DRINK) or a non-caloric solution in self-selected volumes when consuming 3×glucose (20 g) gels (G-GEL) or glucose-fructose (13 g glucose+7 g fructose) gels (GF-GEL) per hour. Fluid intake (DRINK: 1 557±182, G-GEL: 473±234, GF-GEL: 404±144 ml) and percent body mass loss (DRINK: - 0.8±0.9, G-GEL: - 2.0±0.6, GF-GEL: -2.3±1.1) were different (P<0.05) between conditions, though race time did not differ (DRINK: 110.6±14.4, G-GEL: 110.3±14.6, GF-GEL: 113.7±12.8 min). In G-GEL, there was a positive correlation (P<0.05) between body mass loss and race time. Plasma glucose was lower (P<0.05) in GF-GEL compared with other conditions, and total CHO oxidation (DRINK: 3.2±0.5, G-GEL: 3.0±0.4, GF-GEL: 2.6±0.4 g/min) was lower (P=0.06) in this trial. Self-selecting fluid intake but maintaining high CHO availability does not impair half-marathon performance. Additionally, consuming glucose-fructose mixtures in sub-optimal amounts reduces plasma glucose and total rates of CHO oxidation.
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: M J C
authors.initials: MJ
authors.lastname: Lee
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: K M
authors.initials: KM
authors.lastname: Hammond
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Vasdev
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: K L
authors.initials: KL
authors.lastname: Poole
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: S G
authors.initials: SG
authors.lastname: Impey
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: G L
authors.initials: GL
authors.lastname: Close
authors.affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: J P
authors.initials: JP
authors.lastname: Morton
mesh_terms: D000328:Adult; D001628:Beverages; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D004734:Energy Metabolism; D005260:Female; D005632:Fructose / Q000008:administration & dosage; D005947:Glucose / Q000008:administration & dosage; D006801:Humans; D008297:Male; D010807:Physical Endurance / Q000502:physiology*; D015532:Rehydration Solutions; D012420:Running / Q000502:physiology*; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D015532:Rehydration Solutions; D005632:Fructose; D005947:Glucose