In endurance sports “peaking” refers to the art of attaining maximum performance capacity on the day of a major competition.

Peaking is important because the human body is not capable of sustaining maximum performance capacity for a long period of time. If it were, athletes could compete at 100 percent of their potential whenever they pleased. But the training that is required to squeeze out the last 5 percent of one’s potential can be kept up only for a matter of weeks. After that it’s necessary to rest and regenerate. Then, the athlete can start to build toward another peak.

Traditionally, peaking has been thought of as an entirely physiological phenomenon. The training load is increased step by step over a period of weeks and the body adapts, becoming stronger and stronger. However, there is evidence that—at least for experienced athletes who are always very fit—peaking may be largely a psychological phenomenon.

College cross-country runners, for example, usually start their season with a solid base of fitness that they built up over the summer. They then try to build toward a performance peak that is timed to coincide with the championship races at the end of the season. In a 2010 study, researchers Corey Baumann and Thomas Wetter measured a number of performance variables (anaerobic power, VO2max, running economy, ventilatory threshold, and lactate threshold) in members of the University of Wisconsin-Stevens Point Men’s Cross Country Team at the start of a cross country season and again at the end. Anaerobic power actually decreased significantly while all of the other variables were unchanged. Yet most of the runners produced faster race times at the end of the season than they did at the beginning and reported feeling fitter as well.

How were these runners able to race faster despite not getting physically fitter? Baumann and Wetter speculated that psychological factors might be responsible. Specifically, as the season unfolded, the runners’ pain tolerance might have increased through exposure to pain in hard workouts and minor races. Also, their motivation might have increased as the more important championship races drew nearer.

Interestingly, psychologists have learned that willpower, much like physical endurance, is a limited resource. In his book, Willpower, psychologist Roy Baumeister wrote, “You have a finite amount of willpower that becomes depleted as you use it.” When you put a lot of willpower into some challenge you must then take a mental break and replenish it before you can be mentally ready for another challenge. But, again like physical endurance, willpower can also be increased through training. Baumeister wrote that “willpower, like a muscle, becomes fatigued from overuse but can also be strengthened over the long term through exercise.”

What this means is that the art of peaking applies to both physical and mental challenges (partly because physical challenges are also mental). You can’t expect to perform at 100 percent of your potential every day. It’s better to choose a finite number of important goals to pursue and work incrementally toward each, then give yourself a well-earned break after you’ve achieved them.