What’s the best type of cross-training when you’re injured? The first criteria is that it does not aggravate your injury. Doing the elliptical trainer if you have a stress fracture in your foot, for example, will just prolong your recovery.
After that, the most important criteria isn’t which activity most closely mimics the mechanics of running or makes it easiest to keep your heart rate elevated. It’s simpler than that: Which one are you most likely to do with the greatest regularity? Deep-water running, especially if you do hard intervals, is an excellent kissing-cousin substitute for real running. But if the closest pool is 20 miles away and allows deep-water running only at 6:00 AM, well, come on, let’s be realistic about how often you’ll get there. Of the obvious choices—deep-water running, cycling, using an elliptical trainer, using a stair machine—pick the ones that are most convenient for you to do daily.