At its essence, an ultra is a binary equation made up of hundreds of yes/no questions: Eat now or wait? Bomb down this hill, or throttle back and save the quads for the flats? Find out what is itching in your sock, or push on? Extreme distance magnifies every problem (a blister becomes a blood-soaked sock, a declined PowerBar becomes a woozy inability to follow trail markers), so all it takes is one wrong answer to ruin a race.