The author immerses himself in the ultra marathoning community and finds, and compellingly describes, the kind of people that run 100 miles, up and down mountains, in the desert, in the summer, for fun. Then he finds a hidden tribe of Taruahmara Indians in the remotest mountains of Mexico, a tribe that runs ultras as a way of life. He recounts a race between the best of the American nutters and the best of the Taruahamara and along the way makes running sound exhilarating and running shoes sound like an enormous, overpriced hoax guaranteed to induce injuries. August 2009.