Before the Tarahumara run long, they get strong. And if I wanted to stay healthy, Eric warned me, I’d better do likewise. So instead of stretching before a run, I got right to work. Lunges, pushups, jump squats, crunches; Eric had me powering through a half hour of raw strength drills every other day, with nearly all of them on a fitness ball to sharpen my balance and fire those supportive ancillary muscles. As soon as I finished, it was off to the hills. “There’s no sleepwalking your way up a hill,” Eric pointed out.