Running is a great form of aerobic exercise. It burns a lot of calories, helps keep your heart young, and strengthens your muscles and bones. But running too far, too fast, too soon can strain your muscles and put you at risk for injury. In fact, about 7 out of 10 runners are hurt every year. Avoid slanted, uneven pathways. It's best to run on soft, flat ground. And if running causes you pain, stop and take a break. See a doctor if the pain continues for more than a few days. Follow the links below to find WebMD's comprehensive coverage about running, from the health benefits to the best running shoes, and much more.