Self-selecting Fluid Intake while Maintaining High Carbohydrate Availability Does not Impair Half-marathon Performance

We aimed to test the hypothesis that self-selecting fluid intake but maintaining high exogenous CHO availability (60g/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 3xglucose (20g) gels (G-GEL) or glucose-fructose (13g glucose+7g fructose) gels (GF-GEL) per hour. Fluid intake (DRINK: 1557 +/- 182, G-GEL: 473 +/- 234, GF-GEL: 404 +/- 144ml) 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 +/- 12.8min). 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 +/- 0.4g/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.