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Carbohydrate In The Mouth Enhances Activation Of Brain Circuitry Involved In Motor Performance And Sensory Perception

Posted:  Tuesday, July 08, 2014

Swishing a sports drink around in your mouth and then spitting it out might sound like a nonsensical way to boost performance, but it's been nearly a decade since research first suggested that rinsing improves your workout. A found that during an hour-long workout, cyclists who swished carbohydrate-rich sports drinks for longer covered more distance and felt less tired than after a five-second rinse or rinsing with water.

It has to be real carbohydrates, though; the scientists used a solution of water and a flavorless starch derivative called maltodextrin. Artificial sweeteners have no effect.

Simply swilling a 6% concentration maltodextrin solution around the mouth for 5 seconds and then spitting it out a total of eight times every 2 minutes was enough to improve power output. Interestingly, the improvement in power output seemed confined to the first 5 seconds of the sprint, suggesting that there is a small window of effect for a carbohydrate mouth rinse on sprint performance.

And the scientists think they have figured out why it works. It appears that the brain can sense carbohydrates in the mouth, even tasteless ones. The sensors are different from the ones for sweetness, and they prompt the brain to respond, spurring on the athlete.

Many athletes depend on sugary beverages to keep them going. But often, when blood is diverted from the stomach to working muscles during intense exercise, drinks or foods cause stomach cramps. So a carbohydrate rinse can be a way to get the same effect.

Until then, exercise scientists thought they knew why it could help to eat or drink carbohydrates during a long endurance event like a marathon. Muscles can use up their glycogen, the storage form of glucose, during long exercise sessions. But if athletes consume carbohydrates, they can provide a new source of fuel for their starving muscles.

That theory predicts that carbohydrates should have no effect on performance in shorter races, an hour or less. Muscles can’t use up their glycogen that fast, and by the time the body metabolizes the carbohydrates for fuel, the race is almost over.

Then came a handful of studies showing that carbohydrates did have an effect in short exercise sessions. Athletes, often trained cyclists, rode hard and fast for an hour or so after drinking either a beverage containing carbohydrates or one that tasted the same but contained an artificial sweetener.

In intense exercise sessions lasting more than half an hour, the athletes were able to go faster or keep going longer when they had the drink with carbohydrates. Their performance improved as much as 14 percent.

Not only does the rinse give you a performance boost of about 2 percent, but it also helps avoid indigestion from swallowing carbs during workouts. "When performing high-intensity exercise lasting less than 60 minutes, using a carbohydrate rinse for 5-10 seconds can improve performance," says experts. "It could potentially allow you to train harder." If you're doing a couple hours of exercise, however, rinsing will start to lose its effect since your muscles really do need more carbs.