Contrary to popular wisdom, the cure for shin splints and stress fractures isn’t fewer miles and dirt trails. Vanderbilt University researchers found these injuries are more often due to muscle contractions, not hard surfaces. Consider that the force of bone hitting pavement is about twice a person’s body weight. But when you run, the calf muscle squeezes the shinbone up to 14 times harder than it does when you’re standing. Calf-strengthening exercises can help. And when you’re sore, take a day off, giving bones, tendons, and muscle time to heal. “If bone repair can’t keep up with the workload, microcracks—or stress fractures—in the bone accumulate and become painful,” says study author Karl Zelik.