What is carbohydrate mouth rinsing?
Carbohydrate mouth rinsing is simply swilling, not swallowing, a carbohydrate-based drink around your mouth before spitting it out. Carbohydrate mouth rinsing is predominantly used during endurance exercise that lasts more than 45 minutes. Powerade, Gatorade and Lucozade sport are common carbohydrates-based sports drinks used for this purpose.
Why do it?
The process of carbohydrate mouth rinsing acts on the central nervous system (brain) to mask fatigue and reduce perceived excretion. This then allows athletes to keep exercising for longer and therefore has the potential to improve performance. The notion of rinsing and spitting stimulates the oral sensors that tell the brain carbohydrates are on the way. It may be more beneficial for athletes to swallow the drink and make use of the extra calories but this method is very useful for athletes who struggle to keep anything down during moderate to high intensity exercise of at least 1hr duration.
Does carbohydrate mouth rinsing actually work?
During an event, rinsing your mouth with a carbohydrate drink may reduce the perception of fatigue via the central nervous system. Researchers have found that simply rinsing the mouth with a carbohydrates drink for 5-10 seconds improves performance even when the drink isn't swallowed. Another study found that runners ran faster and covered more distance during a 30 minute treadmill run when they mouth rinsed compared to a placebo.
However, the benefits of mouth rinsing may be greater when exercising in a glycogen depleted state or in a fasted state (not eating before exercising). Researchers found that cyclists who were in a glycogen depleted state performed better in a 1 hour stimulated time trial following an overnight fast compared to those who had a meal prior to the time trial. The performance benefits seem to be higher when mouth rinsing is combined with caffeine during high intensity exercise.
It seems the ergogenic (performance enhancing) effect of mouth rinsing is due to its impact on carbohydrate receptors in the mouth, signalling to the brain that the food is on its way. Despite not actually consuming any carbohydrates, these sensors activate the brain's pleasure and reward centres. It overrides the perception of effort and fatigue so the athlete is able to continue exercising.
For exercise lasting 45-75 minutes, consuming any carbohydrates isn't necessary but simply rinsing the mouth with a carbohydrate drink or even sucking on a sweet will be enough to give a performance boost. For athletes who find it difficult to consume anything during exercise this strategy is particularly beneficial, especially if gastrointestinal problems are also experienced when consuming carbohydrates during high intensity exercise or competitions/events lasting longer than 1hr. Gastrointestinal problems are particularly common for endurance athletes, due to a number of mechanical, physiological and nutritional causes.
In summary, carbohydrate mouth rinsing is a great strategy to use, particularly for endurance athletes, during exercise to improve performance and prolong exercise duration. Many studies have found that athletes who used this technique run faster or cover more distance during their event. If athletes are prone to gastrointestinal problems during exercise, mouth rinsing is a useful tool to avoid this. Studies have shown that simply rinsing the mouth with a carbohydrate drink for 5-10 seconds improves performance.
References
Carter, James & Jeukendrup, Asker & Jones, David. (2004). The Effect of Carbohydrate
Mouth Rinse on 1-h Cycle Time Trial Performance. Medicine and science in sports and
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Rollo I, Williams C, Gant N, Nute M. The influence of carbohydrate mouth rinse on
self-selected speeds during a 30-min treadmill run. Int J Sport Nutr Exerc Metab. 2008
Dec;18(6):585-600. doi: 10.1123/ijsnem.18.6.585. PMID: 19164829.
Lane SC, Bird SR, Burke LM, Hawley JA. Effect of a carbohydrate mouth rinse on
simulated cycling time-trial performance commenced in a fed or fasted state. Appl
Physiol Nutr Metab. 2013 Feb;38(2):134-9. doi: 10.1139/apnm-2012-0300. Epub 2012
Nov 26. PMID: 23438223.
Bean, A,. 2017, Complete Guide to Sports Nutrition. [S.I]: Bloomsbury Sport