As seen in the National Geographic Complete Guide to Brain Health
Your body and mind are connected by nerve bundles, which move muscles and keep your organs functioning. Sensory stimuli is provided to the brain through these nerves. A healthy brain therefore starts with a healthy body. Athletes have more than likely been focusing on athletic performance, perhaps without even realizing the affect your physical activity has on your brain. For those of us who quit exercising abruptly (perhaps because of an injury, or because of getting so sick of pushing the body for hours, years on end), may therefore not know the affect that a lack of exercising has on the brain.