Exercise is good for the brain as well as the body and may even protect it against the ravages of old age, U.S. researchers say. Researchers at the University of Wisconsin in Milwaukee showed that the benefits of exercise were not limited to the young by testing the brains of middle aged sedentary rats and their more active counterparts. They found that the density of blood vessels in the brains of active rats who exercised on a tread wheel had increased dramatically in the first three days of activity.