Most endurance athletes know they need 45 to 90 grams of carbohydrates per hour for efforts lasting over 2.5 hours to prevent glycogen depletion.
But what if your session is shorter? Say, one hour of high-intensity effort?
There typically is no benefit to fueling for short efforts—your stored glycogen should be adequate. However, you can still get a performance boost from carbohydrates without actually consuming them.
This technique is called mouth rinsing.
What is Mouth Rinsing?
Carbohydrate mouth rinsing is exactly what it sounds like: you swish a carbohydrate-based drink in your mouth for a few seconds, then spit it out. The idea is to trick your brain into thinking you are consuming carbohydrates.
This simple neural trick works: multiple studies show it can boost performance by 2% to 3%, especially during high-intensity efforts lasting around an hour.
Why Mouth Rinsing Works
The secret of mouth rinsing lies in the brain, not the muscles. Your mouth contains specialized carbohydrate receptors that detect the presence of energy. When you rinse with a carbohydrate-based solution, these receptors send signals to the brain. The brain thinks it is getting energy, even if you never swallow the fuel.
This was seen in a landmark study. Researchers had athletes do mouth rinsing and then looked at their brains using fMRI imagery. They found mouth rinsing activated regions of the brain involved in motivation, motor control, and reward processing—leading to a measurable decrease in perceived exertion and an increase in performance.
In short, mouth rinsing helps the brain believe it's fueled, which allows the body to:
- Push harder with less discomfort
- Delay fatigue
- Maintain focus
- Increase power output
What the Research Says
- A review of 11 randomized trials found that carbohydrate mouth rinsing improved endurance performance in time trials lasting around 1 hour, with performance increases of 2% to 3% on average (Jeukendrup & Chambers, 2010).
- In one trial, cyclists who rinsed with a carb solution during a 1-hour time trial produced significantly more power and finished faster than those who rinsed with artificially sweetened water (Carter et al., 2004).
- A 2024 study from the University of Georgia found similar improvements in resistance-trained athletes, suggesting that mouth rinsing could also help during strength or mixed-mode workouts—not just endurance efforts (UGA, 2024).
When to Use It
Mouth rinsing seems to be most effective for high-intensity efforts lasting 30 to 70 minutes, such as:
- Short races or time trials
- Interval sessions
- Warm-ups before a longer event
- Any shorter session where you want to push hard but don’t want to take in carbohydrates
Mouth rinsing is not a substitute for fueling during longer sessions. After ~90 minutes of effort, your glycogen stores run low, so fueling is necessary.
How to Do Mouth Rinsing
- Mix a carbohydrate drink like Nrgy Drink.
- Swish a small mouthful in your mouth for 5 to 10 seconds.
- Spit it out.
Note: Plain water or artificially sweetened drinks don’t have this effect. The drink must contain actual carbohydrates—glucose, fructose, or a combination.
Why Spit It Out?
It’s important that the mouth-rinsing lasts at least five seconds, so tongue receptors have time to detect the carbohydrates and send signals to your brain. You can swallow or spit the drink. However, spitting is better if you want to avoid carbohydrate intake for:
- Weight management: Not fueling during your session makes it easier to stay in energy balance.
- GI distress: No undigested fuel in the gut means less chance of problems.
- Training low: Some carbohydrate periodization methods involve not fueling during sessions.
Bottom Line
Mouth rinsing is a simple but effective tool for boosting performance without actual fueling. It’s science-backed, fast-acting, and ideal for short, intense, or fasted sessions.
If you’re racing or training hard but don’t want the gut load or calories—just swish and go.