Want to improve performance? Rinse your mouth with Gatorade

Well known to endurance athletes are the benefits of carbohydrate during exercise lasting more than an hour. Ingesting the appropriate amount (the recommended amount is 40-60 g/hr, which is equivalent to 2/3-1 liter of Gatorade per hour) improves endurance performance. The effect of eating carbohydrate is to maintain optimal rates of carbohydrate use in the muscle, with or without sparing the glycogen stores. This becomes particularly important during the latter stages of endurance exercise when liver glycogen stores are too low to maintain blood glucose and avoiding hypoglycemia becomes difficult.

During exercise lasting 1 hour or less, the evidence for rationalizing carbohydrate ingestion is less clear. Some studies indicate that ingesting carbohydrate during this short period does indeed improve performance, while others have not observed this. Because of the lack of consensus, carbohydrate ingestion during periods of exercise lasting less than 1 hour has never been vigorously recommended.

Interestingly enough, there is some evidence that simply mouth rinsing with a carbohydrate drink improves performance, at least in cyclists. When given a carbohydrate drink just as a mouth rinse, some athletes began to feel better and were able to pick up the pace without having swallowed the carbohydrate. These results suggest that the brain may be monitoring the carbohydrate stores in the body. If the brain recognizes the carbohydrate in the mouth, it may be receiving signals that indicates an incoming energy source. In anticipation of its energy source, the brain may alter its response to exercise, resulting in a selected faster pace.

To further investigate this effect, Rollo and colleagues from Loughborough University in the UK tested carbohydrate mouth rinsing on runners during a 30-min treadmill run. These investigators did something alittle different from traditional performance studies. One way to test performance in the laboratory is to quantify power output or distance during a set amount of time and allow the athlete to adjust the pace accordingly. This is relatively easy to do with cyclists because the athlete simply has to increase or decrease his or her pedal rate to affect power output. But for runners on a treadmill, changing the running pace is less spontaneous and requires manual adjustment of the treadmill speed. To overcome this limitation, these investigators used an automated treadmill where the speed of the treadmill was automatically changed when the runner simply moved to the front or the back of the belt.

Ten endurance trained male runners each ran twice for 30 minutes, once with a placebo and once with a carbohydrate solution mouth rinse provided. The athletes were asked to run at a hard pace and were free to adjust the intensity at any time during the run. The mouth rinse was administered every 5 minutes in an amount of 25 milliliters (5 teaspoons). This study was a double blind (no one knew if the athlete was getting the placebo or carbohydrate solution until after the study was completed) and randomized (the order of the trials ) study.

The investigators found that the carbohydrate mouth rinse did:

• not affect heart rate or sweat rate response
• not affect rating of perceived activation
• improve feelings of "good" at the beginning of exercise, but not after that
• increase pace during the first 5 min resulting in overall improved performance (greater distance covered during the run)

From these results, it appears that simply rinsing your mouth with a carbohydrate solution has some positive effect on performance. The actual improvement in distance was approximately 1/10th of a mile (4.1 vs 4.0), on average. That's an increase in average running pace from 8.0 to 8.2 mph, certainly enough to give someone an advantage during a race.

Why did the benefits only occur at the beginning of exercise? Maybe the brain is too smart to be fooled more than once. If that is the case, the strategy of mouth rinsing may be beneficial only during short duration exercise (less than 1 hour). At least for runners who are prone to GI discomfort during races, a mouth rinse may be an alternative to not drinking anything, at least during 5k or 10k races. Anything longer than that, you are better off swallowing that carbohydrate solution.

Reference: Rollo et al. The influence of carbohydrate mouth rinse on self-selected speeds during a 30-min treadmill run. Int. J. Sport Nutr. Exerc. Metab. 18, 2008.