Has your coach ever recommended that you rinse your mouth with a sports drink instead of drinking it? Have you ever seen athletes on television rinsing their mouths with their bottles and then spitting out the contents? So, is mouth rinsing a myth or a reality?
A little reminder about sports performance
The carbohydrates we consume are transformed into glucose, which can then be used by our muscles to perform. Glucose is our body's #1 source of energy. But glucose can also be stored in the liver or muscles as glycogen. During a short physical effort, our muscles use glucose and glycogen to help us perform (1).
Principle
The principle of carbohydrate mouth rinse is based on the fact that we can potentially trick our brain. Our taste buds are receptors that detect the carbohydrates contained in the drink with which we rinse our mouth. These taste buds send a signal to the brain that energy (glucose) is on its way! The brain, thinking that this is true, sends a signal to the muscles to become more active (2). This is why we can see an increase in sports performance.
The problem? This energy (glucose) will never reach the muscles, since we don't swallow our drink. Rinsing our mouth with a sweet liquid would therefore allow us to trick our brain!
What the science says
The results are rather mixed and the mechanism is still being studied. It could work for some athletes, but not for others (each person is different!) (3). It would also depend on the initial glycogen reserves (2). If one has consumed enough carbohydrates before the effort (which is desirable), one would see less effects than if one had not consumed enough. With little energy to perform, the body would be in "panic mode" and would be more sensitive to the carbohydrates that hit our taste buds.
Even so, carbohydrate mouth rinse could be of interest to more digestively sensitive athletes, as it would reduce the adverse gastrointestinal effects that can occur when consuming carbohydrates during very high intensity exercise (2).
For some athletes only
Is this practice as effective for a marathon runner as for a sprinter? No! It would only be effective for sports with a maximum duration of one hour of moderate to high intensity (1, 4), i.e. sprinting, speed skating, field hockey and soccer of short duration, etc. However, it is important to mention that this practice is for high level athletes, where a fraction of a second can make a difference.
Beware of the frequency!
If we rinse our mouths all the time, it is very likely that our brain will become aware of the trick we are trying to pull. So why not save this technique for competition days only?
A word of caution
Just because carbohydrate mouth rinse might have its benefits, it doesn't mean we should abandon our good hydration practices during exercise! Staying well hydrated and consuming an adequate amount of carbohydrates should remain a priority, especially when the effort lasts more than an hour. It is therefore important to consult your sports dietitian to ensure that you perform well while protecting your health!
References:
- Ledoux, M., Lacombe, N., & St-Martin, G. (2019). Nutrition, sport et performance. Vélo Québec éditions.
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de Ataide e Silva, T. et al. (2013). Can carbohydrate mouth rinse improve performance during exercise? A systematic review. Nutrients.
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Ferreira, A. M. et al. (2018). The effect of carbohydrate mouth rinse on performance, biochemical and psychophysiological variables during a cycling time trial: a crossover randomized trial. Journal of the International Society of Sports Nutrition.
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Clarke, N. D. et al. (2017). Carbohydrate mouth rinse improves morning high-intensity exercise performance. European journal of sport science.
