Focus: cardio + agility + balance
Week one starts with a half-hour run at PE 6 on a gently sloping trail with obstacles like rocks, trees, and logs. "Pretend it's a ski run, says Davenport, who prefers to run uphill, bounding off boulders and dodging trees.
To preserve his knees, after running up 11,212-foot Aspen Mountain, Davenport takes the gondola down. If you don't have a lift, descend gingerly—half walking, half jogging—absorbing the impact with your muscles instead of your joints. By week four, the plan calls for intervals that will max your heart rate and test your agility.