A fundamental goal of healthy aging is to keep walking as long as possible. Barring an injury or disabling disease, most of us think of the ability to walk as a defining capability of the human body. Of course, people who lose their ability to walk can still retain mobility through wheelchairs and assistive devices, and they can have full and happy lives. But there’s no reason why most people can’t keep walking their whole lives. It’s important to stay active in order to maintain this ability—or, if you haven’t been active for a while, to start with whatever simple measures it takes to boost your level of activity and start improving mobility.