Mouth rinsing with a bitter solution without ingestion does not improve sprint cycling performance.

PURPOSE: Recently, we have shown that combining mouth rinsing with the ingestion of a 2 mM quinine solution immediately before a 30-s cycling sprint significantly improves performance. However, the strong bitterness of such a solution produces an unpleasant taste and evokes nausea at higher concentrations. Given the possibility that mouth rinsing with quinine without ingesting it may not produce nausea, a mouth rinse only protocol may be a more practical approach to administer quinine for improving exercise performance. The purpose of the present study was to determine whether mouth rinsing with quinine without ingesting it improves 30-s sprint cycling performance. METHODS: Twelve competitive male cyclists performed a 30-s maximal cycling sprint immediately after rinsing their mouth for 10 s with either a 10 mM bitter quinine solution (QUI), plain water (WAT), a 7.1 % w/v sweet glucose solution (GLU), or no solution at all (control; CON). Sprint performance was assessed, and heart rate, ratings of perceived exertion and blood variables were measured pre- and post-exercise. RESULTS: Mean power output during the 30-s sprint (QUI 888 ± 38; CON 873 ± 39; WAT 885 ± 37; GLU 873 ± 42 W; p = 0.431) as well as peak power (QUI 1230 ± 61; CON 1,208 ± 65; WAT 1,220 ± 70; GLU 1,202 ± 59 W; p = 0.690) were similar between the four conditions. There were no significant differences in any other performance measures, heart rate, subjective ratings or blood variables between conditions. CONCLUSIONS: Mouth rinsing with a bitter tasting quinine solution without ingestion does not improve 30-s sprint cycling performance.

Mouth rinsing and ingestion of a bitter-tasting solution increases corticomotor excitability in male competitive cyclists.

PURPOSE: Recently, we have shown that the combination of mouth rinsing and ingesting a bitter-tasting quinine solution immediately prior to the performance of a maximal 30-s cycling sprint significantly improves mean and peak power output. This ergogenic effect was proposed to be related to the activation of the corticomotor pathway by afferent taste signals originating from bitter taste receptors in the oral cavity. The aim of the present study was to use single-pulse transcranial magnetic stimulation to investigate whether mouth rinsing and ingestion of a bitter quinine solution increases corticomotor excitability. METHODS: A series of 10 motor-evoked potentials (MEPs) were recorded from the relaxed first dorsal interosseus muscle in 16 male competitive cyclists immediately before and after they rinsed their mouth for 10 s and then ingested either a 2 mM bitter quinine solution or plain water. RESULTS: Mean MEP amplitude was significantly increased in response to quinine administration by 16% (p < 0.05), with no evidence of a time-dependent effect over the 10 pulses. Mean MEP amplitude also increased by 10% in response to water administration (p < 0.05), though this increase was significantly smaller than the response to quinine (p < 0.05). CONCLUSIONS: We conclude that the activation of bitter taste receptors in the oral cavity and upper gastrointestinal tract has the capacity to increase corticomotor excitability in male competitive cyclists.

Opposition of carbohydrate in a mouth-rinse solution to the detrimental effect of mouth rinsing during cycling time trials.

Studies have reported that rinsing the mouth with a carbohydrate (CHO) solution improves cycling time-trial performance compared with rinsing with a placebo solution. However, no studies have compared the effect of mouth rinsing with a no-mouth-rinse control condition. The aim of this study was to compare the effects of a CHO mouth rinse with those of a placebo rinse and a no-rinse condition. Ten male cyclists completed three 1,000-kJ cycling time trials in a randomized, counterbalanced order. At every 12.5% of the time trial completed, participants were required to rinse their mouths for 5 s with either a 6.4% maltodextrin solution (CHO), water (WA), or no solution (CON). Heart rate and ratings of perceived exertion (RPE) were recorded every 25% of the time trial completed. Time to completion was faster in both CHO (65.7 ± 11.07 min) and CON (67.6 ± 12.68 min) than in WA (69.4 ± 13.81 min; p = .013 and p = .042, respectively). The difference between CHO and CON approached significance (p = .086). There were no differences in heart rate or RPE between any conditions. In summary, repeated mouth rinsing with water results in decreased performance relative to not rinsing at all. Adding CHO to the rinse solution appears to oppose this fall in performance, possibly providing additional benefits to performance compared with not rinsing the mouth at all. This brings into question the magnitude of the effect of CHO mouth rinsing reported in previous studies that did not include a no-rinse condition.

New Insights into Enhancing Maximal Exercise Performance Through the Use of a Bitter Tastant.

It is generally acknowledged that for an orally administered ergogenic aid to enhance exercise performance it must first be absorbed by the gastrointestinal tract before exerting its effects. Recently, however, it has been reported that some ergogenic aids can affect exercise performance without prior absorption by the gastrointestinal tract. This is best illustrated by studies that have shown that rinsing the mouth with a carbohydrate (CHO) solution, without swallowing it, significantly improves exercise performance. The ergogenic effects of CHO mouth rinsing in these studies have been attributed to the activation of the brain by afferent taste signals, but the specific mechanisms by which this brain activation translates to enhanced exercise performance have not yet been elucidated. Given the benefits of CHO mouth rinsing for exercise performance, this raises the issue of whether other types of tastants, such as bitter-tasting solutions, may also improve exercise performance. Recently, we performed a series of studies investigating whether the bitter tastant quinine can improve maximal sprint performance in competitive male cyclists, and, if so, to examine some of the possible mechanisms whereby this effect may occur. These studies have shown that mouth rinsing and ingesting a bitter-tasting quinine solution can significantly improve the performance of a maximal cycling sprint. There is also evidence that the ergogenic effect of quinine is mediated, at least in part, by an increase in autonomic nervous system activation and/or corticomotor excitability. The purpose of this article is to discuss the results and implications of these recent studies and to suggest avenues for further research, which may add to the understanding of the way the brain integrates signals from the oral cavity with motor behaviour, as well as uncover novel strategies to improve exercise performance.

Mouth rinsing and ingesting a bitter solution improves sprint cycling performance.

PURPOSE: There is evidence that carbohydrate (CHO) mouth rinsing can improve endurance exercise performance as well as muscle force production and sprint performance. Whether the oral administration of non-CHO tastants also affects exercise performance is not known. The purpose of this study was to investigate whether mouth rinsing and ingesting a bitter-tasting solution of quinine improves maximal sprint cycling performance. METHODS: Fourteen competitive male cyclists performed a 30-s maximal cycling sprint immediately after rinsing their mouth for 10 s and then ingesting a 2-mM bitter quinine solution, plain water, a 0.05% (w/v) sweet aspartame solution, or no solution at all (control). Cycling power output was recorded during the sprint. Heart rate, perceived exertion, blood lactate, and blood glucose were measured preexercise, immediately postexercise, and 7 min postexercise. RESULTS: Quinine significantly improved mean power output by 2.4%-3.9% compared with the three other conditions [P ≤ 0.021, effect size (ES) = 0.81-0.85]. Peak power output in the quinine condition was higher compared with the water (3.7%, P = 0.013, ES = 0.71) and control (3.5% P = 0.021, ES = 0.84) conditions but was not significantly different from aspartame (1.9%, P = 0.114, ES = 0.47). There were no significant differences in cycling performance between water, aspartame, and control conditions. There were no differences in heart rate, perceived exertion, or blood variables between any of the conditions. CONCLUSION: This study shows for the first time that mouth rinsing and ingesting a bitter-tasting solution immediately before a maximal sprint exercise can improve performance.