Neurologist Scott Grafton is a big believer in the healing power of the outdoors. “Take old people out of a complex environment and they age quicker,” he notes. “The brain doesn’t just need physical activity to remain vital, but complex physical activity—the brain needs it to stay healthy and engaged.” Something as simple as walking in a new environment provides this critical brain input. Your feet have to adjust to different surfaces and angles, your ankles need to move in conjunction with your feet.