Whether you are a hard-core runner or a novice, choosing a good running shoe is essential for preventing injury and helping you enjoy your running. When running, your foot absorbs up to four times your body weight every time your heel hits the ground, and this event is repeated almost 1,000 times with every mile you run. To put it in perspective, a 150-pound runner absorbs about 120 tons of force during a one-mile run. Your running shoe is your first line of defense in protecting your body from these tremendous forces. In this article, Michael Gross, M.D., section chief of Sports Medicine and orthopedic director of the Center for Sports Medicine at Hackensack University Medical Center, offers 12 simple guidelines to help when people shop at the running shoe store.