" Hill training ranks among the best training for three basic reasons, one of them less obvious than the others. Climbing hills is hard work and tests both the heart (cardiovascular training) and the legs (strength training). You can't get a better combination.
Running uphill also lessens the impact force of each footfall. Impact force is a major contributor to the overuse injuries that trouble many runners. This means that there is less risk to training hard on the hills several times a week than there is to training hard on a track or other surface. Many coaches and distance runners realize this and use hill training to great benefit. (Be careful running downhill, as this increases impact force and injury potential.)As with any kind of new workout, you should begin hill training easily and gradually. The simplest hill workout is a medium-distance run that includes several good hills on the route. If you live in a suburban neighborhood with many roads, you could find a hilly street and loop up it several times on your run. "