Is Carbohydrate Rinsing the Future of Refuelling?
Published at 1 May 2019

Can rinsing then spitting carbs really be the answer to on-the-go fuelling?

 

Numerous studies over the past 30 years have shown that consuming carbohydrate drink to replenish stores on the move (or at the very least, slow down the rate at which your body’s stores of muscle glycogen are depleted) prolongs time to exhaustion and improves endurance performance.

More recent studies have created a bit of mystery around carbohydrate and shorter duration performance. A study twelve years ago discovered that cyclists performing a 40km time trial were on average one minute faster if they had a carbohydrate drink during the trial. This was unexpected because:

- during exercise of one hour or less, low blood sugar doesn’t develop

- it takes time for ingested carbohydrate to be absorbed, transported to and used by the muscles, so only a small amount of the carbohydrate drink was actually used as fuel. 

Even stranger was the finding that if this carbohydrate was fed to the cyclists through a drip, it had no effect on performance whatsoever - it had to be drunk.

Scientists are now convinced that the above effect occurs as a result of ‘brain-mouth’ connection. Carbohydrate receptors in the mouth send positive signals to three main areas in the brain. These signals are integrated with fatigue signals from the muscles and an appropriate motor output (i.e. less perceived fatigue) is generated.

The study was later repeated with one major change - instead of drinking the carbohydrate drink, the cyclists rinsed their mouths with it and then spat it out again - the effect on performance was the same as when the carbohydrate was ingested. The theory is that when you ‘carbohydrate rinse’, carbohydrate sensors in the mouth signal to the brain that food is on its way, thus reducing the perception of effort and making the exercise task easier.

In the last two years a larger number of further studies have been carried out with fairly mixed results. Overall however, the researchers concluded that carbohydrate mouth rinsing seems to improve performance during moderate to high-intensity exercise of at leats 1 hours duration. They also concluded that the benefits of mouth rinsing seem to be accentuated when muscle and liver glycogen stores are reduced - i.e. towards the end of a long bout of exercise - possibly due to a greater sensitivity of the oral receptors later on in exercise. Something else also emerged - a 10 second mouth rinse is better than a 5 second rinse for performance (there is a ‘dose response’ to the duration of the mouth rinse). 

Practical advice

Mouth rinsing studies have shown that it is a less effective practice during shorter bouts of exercise, flat-out exercise or when you’re not already carbohydrate depleted. Another downside of rinsing is simply that for most athletes there doesn’t seem to be a disadvantage in actually swallowing your drink (unless you frequently suffer from gastro-intestinal distress). When training is prolonged for 2 hours or more, carbohydrate is a very important fuel and it is essential to ingest it. 

The advantages can be seen, however, during longer events when you’re already carbohydrate depleted. Another instance is where your carbohydrate drink is running low and you want to eek it out: regular rinsing with small sips over an extended period can be more effective than gulping what you have left in one go. 

When you are carbohydrate rinsing, ensure you rinse for at least 10 seconds, do this every 10 minutes or so. 

Be aware that constant rinsing and swirling around your teeth can be detrimental to your dental health. If you suffer from sensitive teeth use a low-acidity drink formulation.

Carbohydrate Rinsing

 

 

 
 
 
 
 



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