It seems counterintuitive: to run a fast 13 miles on trail, I should prepare by walking. Okay, walking and running, but only running a little bit. As in three days a week, two of which are only for a half hour. So says Jeff Galloway , a runner and coach who has been preaching the benefits of low-impact...

In a few weeks I will run 13.2 miles from Snowmass to Aspen, Colo. in the Golden Leaf Half Marathon. The race starts at 8,650 feet, reaches a pinnacle of about 9,620 feet, and ends at roughly 7,800 feet. Between the altitude and the effort, I'd have to indulge in something illegal to get much higher...