Effect of Low-To-Moderate Exogenous Carbohydrate Supplementation on Time to Exhaustion During Constant Load Intense Cycling in Healthy Individuals. A Double-Blind, Randomised and Placebo-Controlled Crossover Trial

Exogenous carbohydrate (CHO) supplementation during exercise is an efficient strategy to enhance endurance performance. However, the effects of low-to-moderate amounts of exogenous CHO on time to exhaustion (TTE) have not been fully investigated. Nineteen healthy moderately active participants (26.2 ± 1.7 years and BMI: 22.4 ± 2.3 kg·m⁻²) performed four TTE tests at the second lactate turn point (LTP2) in a double-blind, randomised and placebo-controlled setting consuming either 20, 40 and 60 g·L⁻¹·h⁻¹ of a glucose and fructose combination (CHO_20, CHO₄₀ and CHO₆₀) or a placebo (PLA). Glucose [Glu⁻] and lactate concentrations [La⁻] as well as ventilatory, heart rate (HR) and rating of perceived exertion (RPE) values were recorded during the tests. There were no statistically significant differences in TTE (PLA: 32.5 ± 9.6 min, CHO₂₀: 35.9 ± 14.5 min, CHO₄₀: 35.1 ± 12.9 min, CHO₆₀: 38.0 ± 17.5 min and p = 0.11). Within each trial arm, no statistically significant differences were found between pre- and post-exercise [Glu⁻] (p > 0.05). Post-exercise [Glu⁻] for CHO₆₀ were significantly higher when compared to PLA (p = 0.03). Lastly, mean ventilatory parameters as well as HR and RPE during exercise showed no statistically significant differences between trial arms (p > 0.05). Low-to-moderate amounts of exogenous CHO do not increase TTE in healthy moderately active individuals when compared to a placebo. Therefore, when exercising for less than 60 min at high intensities, exogenous CHO supplementation is not necessary if a CHO rich diet is followed prior to exercise.

Trial Registration

DRKS-ID: DRKS00030531