Oral Carbohydrates Linked to Boost in Cycling Performance

Carbohydrates in mouth may activate brain regions involved in reward and motor activity

TUESDAY, April 21 (HealthDay News) -- The improvement in athletic performance that follows the presence of carbohydrates in the mouth may be due to brain responses linked to reward, according to research published April 1 in the Journal of Physiology.

Edward S. Chambers, Ph.D., of the University of Birmingham in the United Kingdom, and colleagues conducted two studies, each featuring a group of eight trained cyclists who completed a time trial equivalent to cycling an hour at 75 percent maximum power output. In the first study, they rinsed their mouths with glucose solution or saccharine-sweetened placebo. In the second, they rinsed with maltodextrin or placebo. Corresponding functional MRI studies assessed brain changes in response to these liquids in other subjects.

Both groups of cyclists completed the cycle time trial faster with glucose or maltodextrin than placebo. The functional MRI studies found that glucose - but not saccharine - activated reward-related regions of the brain, and that similar brain activation patterns were seen in response to both carbohydrate solutions.

"We suggest that activation of these regions of the brain may provide a mechanism to explain the improvement in exercise performance that is observed when carbohydrate is present in the mouth," the authors conclude. "The findings also support the existence of oral receptors sensitive to the caloric value of carbohydrate and which are independent of sweetness."

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