It fascinates me that nonrunners so often seem to think that running long distances must be intolerably boring. 'What do you think about when you're running?' they ask. That question has occasionally been explained as a fundamental difference between what experienced runners do when racing or engaging in training runs expressly intended to practice racing conditions, and the more easygoing runs people do just for fitness or fun, or to build a base to prepare their bodies for more ambitious workouts weeks later. When racing, the runner is like an airplane pilot who is fully engaged in monitoring and adjusting the controls. In this so-called associative mode, the runner is monitoring and adjusting his breathing, heart rate, core temperature, hydration, perspiration, tempo, gait, available energy, electrolyte level, nutrient intake, flirtation with anaerobic or lactate threshold, and of course the conditions of his ambient environment: air temperature and humidity, precipitation, wind velocity and direction, and terrain, all while anticipating the road ahead. Some of it is done subconsciously and some with deep attentiveness. On a more easygoing (or dissociative) run, he might think about his work or family, or replay a recent conversation in his head, or imagine what he'd like to have said in that conversation --or he might notice the wildlife around him with the same appreciation he would when going for a walk in Rock Creek Park or a hike in Yellowstone, or he might chat with a running partner about whether the Cubs will ever win the World Series. That's what runners think about on a long run: sometimes a continuous stream of data about the running itself, and other times a stream of anything from profundity to trivia about whatever.