According to a study by researchers from Denmark and The Netherlands published in the October 2008 print issue of The FASEB Journal, the brain, just like muscles, works harder during strenuous exercise and is fueled by lactate, rather than glucose. Not only does this finding help explain why the brain is able to work properly when the body's demands for fuel and oxygen are highest, but it goes a step further to show that the brain actually shifts into a higher gear in terms of activity. This opens doors to entirely new areas of brain research related to understanding lactate's specific neurological effects.

To reach their conclusion, the researchers looked at research that compared the blood running to and from the heads of volunteers undergoing strenuous exercise. They found that the blood on its way to the brain contained considerably more lactate than blood flowing from the brain.