How can flatlanders train for mountain running?

Run on a treadmill set to a 15-percent-grade.  You can also run stadium stairs, and weight training will help, too. Twice a week, do 20 minutes of training four key muscle groups—quads, hamstrings, hip flexors, and calves—with light weights and high reps. This will help build the muscles you’ll need to conquer the mountains.
—Russ Gill is a professional ultra runner and owner of Bad to the Bone Endurance Sports