member, or friend, or colleague who’s always worrying about the toll running is taking on your knees, hips, and back. You might even be worried yourself. We all know a few one-time runners forced to become swimmers, cyclists, or power-walkers. We wonder

-training protocol outlined by Randy Wilber of the USOC sports sciences department, who suggested the following: first run in the morning or evening cool; then move to warmer times of the day; finally, increase the length and intensity of your midday workouts

runners, walkers and cyclists each time I drive to work? If exercise-produced free radicals are so deadly, why do studies show that the more you exercise, the longer you'll live?As one of the world's leading experts on exercise and immunology, David Nieman