TOOLBOX: “Did you know that you don’t need to ingest your energy drink? A simple carbohydrate mouth rinse for a few seconds can increase your exercise performance…”
At least that’s how I first heard of it 10 years ago while on my Nutrition and Dietetics degree. The thing is, we can still hear coaches and other professionals talk about this the same way as they did 10 years ago: “Just rinse it every now and then. It seems to do something.” Turns out, there’s a proper way of doing it and a proper context to apply it, and it may not be suited when racing.
In previous articles, we have discussed how to properly periodize carbohydrate ingestion according to the session ahead and how to accurately perform a carb-loading protocol when racing.
So what happens now? One day I’m telling you to “feast on carbs” and all of a sudden you should have them for a few seconds in your mouth and can’t even swallow them?
Well, this is called “toolbox” for a reason. Nutrition has become a toolbox full of different tools to use in the right moment.
What exactly is carbohydrate mouth rinse?
Carbohydrate mouth rinsing can be defined as flushing a carbohydrate-based drink around the oral cavity multiples times and for a certain period of time (studies so far have tested this from 5 up to 15 seconds), followed by the subsequent expulsion of fluid. We have just published a research paper if you want to take a look.
So how did scientists come up with the idea of studying the effects of rinsing a carbohydrate drink (without swallowing) on exercise performance?
Back in 2004, Dr. James Carter and his colleagues from the the University of Birmingham infused with either glucose (1 g/min) or saline (placebo) in six endurance trained cyclists and instructed them to complete a set amount of work in a cycle ergometer as quickly as possible. To their surprise, the infusion of glucose did not produce any ergogenic effect over saline infusion.
So, what’s wrong here? We know that ingesting carbohydrates has a direct impact on exercise performance but when we directly infuse glucose, there’s no ergogenic effect? There’s must be something to the ingestion process that is related to this?
So the authors purposed doing a second study to see if there was some ergogenic effect to the simple sensing of carbohydrates in the mouth, without ingestion. Surprisingly again, rinsing with non-sweet maltodextrin for 5 s in regular intervals versus water had a positive effect on a 1h cycling time trial.
What are the studied effects of rinsing carbohydrate-rich drinks in the mouth?
1. It appears that there are taste receptors in the mouth that can influence neural pathways, ultimately leading to improved exercise performance.
2. These receptors in the mouth appear to be sensitive to non-sweet carbohydrates and could directly stimulate reward centers in the brain, leading to a positive “central drive”.
Plenty of research associates carbohydrate mouth rinse to positive effects in athletic performance, not only in endurance activities but also with a growing interest in high intensity sprint-based activities. However, there some aspects to take into account before considering the practical application of this strategy:
Rinsing frequency
It’s definitely not “just rinse it every now and then” with no criteria whatsoever. In order to reproduce the findings from the studies, a carbohydrate drink needs to be rinsed in regular periods of 5 to 10 min, which may not be practical in a lot of contexts.
Type of carbohydrate
All types of carbohydrates tested so far have demonstrated positive and similar results. But the effects are not dependent upon the sweetness of the drink, as maltodextrin is quite tasteless. Artificial sweeteners do taste quite sweet, yet they don’t seem to promote beneficial effects on performance and the same brain areas that are activated when rinsing with carbohydrates, do not appear to be activated when rinsing with artificial sweeteners.
Carbohydrate drink concentration (%)
As for drink concentration, there’s no secret here. Almost all concentrations ranging from 6% up to 17% concentration of CHO seem to work, which is the range of most of commercial fruit juices, sodas and even sports drinks. I would just say that using a sports drink or an isotonic drink to spit it out may be a waste of money when you can use a regular commercial fruit juice, or the cheapest option of all: adding table sugar to water since, sucrose seems to work as well as other CHOs (I’d say at least 2 and half tbsp. per 500ml in your bottle would be required).
Duration of the rinse in the mouth
It took 9 years until researchers started considering that the process mouth rinsing may possibly be detrimental to performance through breathing restriction. Research has been performed using protocols from 5 up to 15 seconds with some greater effect with a slightly superior effect with 10 s, which may restrict even further the utilization of such strategies in moments of higher intensity and increased breathing pattern during exercise. I’d say that aiming for 10 s would be the ideal, aiming for at least 5 s in more physically demanding moments
Fed VS fasted state
The answer would be: when in a fasted state. Higher power output and faster trial times are observed when subjects are in a fasted state VS subjects in a fed state. This has been seen mostly in events lasting between 30 and 75 min.
Putting everything together, what’s the right context to resort to carbohydrate mouth rinse?
1. Rinsing each 5 to 10 min (between 5 to 10s in the mouth)
2. At least 6% carbohydrate concentration
3. Exercise duration from 30 to 75 min
4. Superior effect in a fasted state
In which context of cycling could this apply in terms of duration? That’s an easy answer right? Time trials. But is this truly applicable to time trial events?
Aerodynamics is probably the most important factor during time trial events and maintaining an aero position on the bike is absolutely essential. It may not be practical at all to reach for the drink every 5 or 10 minutes. We don’t even see cyclists eating or drinking during that period. Teams often choose not to carry bottles in the rider’s bikes during such event.
Not even mentioning the fact the cyclists are not in a fasted state when racing in such conditions. Therefore the expectable effects wouldn’t probably be worth the trouble.
Even in mountain bike or cyclocross race-events, this could be even worse given the greater technical skill required to maintain balance, avoid obstacles constantly and produce constant peaks of power output during the race.
What may be the right context to use carbohydrate mouth rinse?
While race-like events may not allow for such strategy to be performed for the reasons I’ve just mentioned, there may yet be an application in a training context, particularly when intentionally training in the fasted state, the typical “sleep-low train-low” as part of a training low strategy.
This may just provide the closest condition in which carbohydrate mouth rinse may actually work: being in a fasted state, ability to rinse frequently with rest intervals that allow for the rinsing duration not to condition your performance as it would happen in a race-like environment.
So in this context, carbohydrate mouth rinse can be performed and it could perhaps help in maintaining or increasing power output during a workout in which we don’t want carbohydrate to be ingested as a strategy to counter the negative effects of training with low carbohydrate availability.
In case you are interested, I have just launched an episode on this topic on my Fuel the Pedal Podcast.
About Gabriel Martins:
Gabriel Martins is a Portuguese Nutritionist with a Master’s degree in Sports Nutrition. He currently lives in Spain where he works with cycling teams and integrates the research group on sports physiology at the University Camilo José Cela in Madrid. Additionally, Gabriel is the Host of Fuel the Pedal Podcast. A show where he interviews researchers, sports nutritionists and cyclists discussing topics related to nutrition and physiology.
Gabriel can be reached for comments at [email protected]. You can also follow him on Instagram, Twitter and Facebook.
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