While it is seldom talked about, one of the most important objectives of a competitive runner’s training is to increase his or her suffering tolerance. The only way to do that is through familiarization. To resist suffering more successfully, dig deeper into those reserves, and perform better in races, you must first break through limits of suffering tolerance in training. Most runners have only physical rationales behind their toughest workouts. That’s okay, because the best workouts to stimulate physical improvement are more or less the same as the best workouts to teach suffering tolerance.