Running is an excellent fitness activity, but it only works when you train within your personal capacity to exercise and recover without breakdown. By following the 10-week program you should see progressive improvement without exceeding any unforeseen limitations.

Wayne L. Westcott, Ph.D., is fitness research director at the South Shore YMCA in Quincy, MA., and author of several fitness books including the new releases, Building Strength and Stamina and Strength Training Past 50.