Ultra marathon man.: [Dean] Karnazes is an ultrarunner. He belongs to a niche of long-distance runners who consider 26.2 miles -- the length of a marathon -- a mere warm-up. Their races, called ultramarathons, are generally between 30 and 150 miles long, often on steep hiking trails, lasting into the night, with no breaks for sleep. Just to complete them requires almost superhuman endurance. And even among ultrarunners, Karnazes is considered something of a machine. Warning: Long article with many amazing stories. May inspire you to do 30-mile runs as warm-ups.