Nutritionists have believed for a number of years that carbohydrates help athletes make it through endurance events by refueling muscles of their glycogen stores. They theorized that if that's the case, carbohydrates should have little to no effect on shorter races since the body doesn't metabolize glycogen that quickly.
Newer studies proved that theory wrong—carbohydrates DID have an effect on shorter races. So HK author, Asker Jeukendrup, and his colleagues began to question why—and what they found was remarkable: just rinsing the mouth with a carbohydrate solution had the same effect as drinking it. They now theorize that that the brain can sense carbohydrates in the mouth and prompt the body to react.
Read the full article at http://www.nytimes.com/2010/07/20/health/nutrition/20best.html?_r=2&scp=20&sq=exercise&st=cse