It had been thought sports drinks boosted athletic performance by providing a hit of sugar, salts, and carbohydrates which the body converts to energy.
This study in the Journal of Physiology finds the carbohydrate drinks sent reward and pleasure signals to areas of the brain. In return, this helped reduce the athlete's perceptions of how heavy the workload was enhancing performance.
Scientist's say much of the energy from carbohydrates in sports drinks is provided by signaling directly from mouth to brain-- rather than providing energy for working muscles.
The theory is it's not the muscles, heart or lungs that ultimately limit performance but the brain itself.