Exercise makes you smarter?

Previous research had linked physical exertion with higher levels of neuronal growth factors known as neurotrophins in the spinal cord and skeletal muscles… The scientists gave rats access to a running wheel for periods ranging from zero to seven days. When they tested cultured cells taken from the animals, they found that those from the runners grew longer extensions known as neurites and that there was a direct correlation between how far the rats ran and how long the neurites became.