The Colour Of An Artificially Sweetened, Non Caloric, Placebo Mouth Rinse Solution Influenced Exercise Performance

PURPOSE: To determine whether the colour of an artificially sweetened solution perceived to be a carbohydrate mouth rinse influences 4km cycling time-trial performance. METHODS: Thirty recreationally trained cyclists (18 male and 12 females; age 37 ± 7 y, V̇O2peak 49 ± 11 ml.kg-1 min-1) completed four main sessions in a randomized, counterbalanced, double-blind, crossover fashion. Participants performed a 4km time-trial following mouth rinsing of one of three artificially sweetened, non-caloric, placebo solutions, one congruent with sweetness (red), one incongruent with sweetness (green) and one without colour. On one occasion, participants performed the exercise without any mouth rinse (control). A linear mixed model including individuals as a random factor and an interaction between experimental condition and participant sex as fixed factors was used for statistical inference on performance (time-to-completion) and perceived sweetness (12-point scale), and an interaction between condition and distance was used for ratings of perceived exertion (RPE). RESULTS: There was a significant improvement in time-to-complete the 4km time-trial with the green solution (coefficient: -18.1s [95%CI -30.6; -5.5],p=0.01) compared to control (486.8s [95%CI 465.4; 508.4]), but no significant differences between other conditions (all p>0.05). Although the interaction between condition and sex was not significant (p>0.06), data visualization suggests a larger effect in all conditions for women compared to men. There was no difference in the sweet perception of the red (-0.13, [95%CI -1.06; 0.80], p=0.77) and green (-0.17, [95%CI -1.10; 0.76], p=0.72) compared to the colourless solution (mean 3.83 [95%CI -3.08; 4.59]). There was an interaction between the green solution and distance on RPE compared to control (0.2 increase per 1km, [95%CI 0.06; 0.5], p=0.01), suggesting a higher increase in RPE as the test progressed. CONCLUSIONS: Mouth rinsing a green colour solution improved cycling time-trial performance and increased RPE, with no difference in perceived sweetness, compared to a control session. These performance effects appeared to be influenced by sex, with larger improvements in women. These results have implications for nutritional studies and performance assessments in real-world sport scenarios. FAPESP