In the late 1880s, an Italian physiologist named Angelo Mosso made a curious observation: He tested the muscular endurance of two fellow professors before and after they administered oral exams and found that after their mental efforts their muscles tired more quickly. It was the first demonstration that mental fatigue affects physical performance—a lesson to remember in the days leading up to a race. Just as you taper your mileage to rest your legs, you should also taper your mind.
Maintaining your goal pace is like holding your finger close to a flame: You have to overcome your inclination to pull away from the discomfort. This “response inhibition” is a mental skill you use in everyday life (when being polite to someone you don't like or passing up a second helping of dessert, for example). But it's a finite resource. Last year, British researchers showed that subjects completing a computer test designed to require response inhibition ran a subsequent 5K time trial 5.3 percent slower than when they completed a similar computer test that didn't require response inhibition.
In a similar—and more bizarre—study, volunteers watched a three-minute video designed to elicit disgust. (It involved eating vomit.) Simply watching the video didn't affect a subsequent 10K cycling time trial compared with not watching it. But when volunteers were asked to hide their emotions while watching the video, they slowed by 3.3 percent in the time trial afterward and reported a higher sense of effort from the start. It was the effort of suppressing their natural response that left the subjects mentally fatigued.
Even visualizing your race can leave your brain tired. Mental imagery can be powerful: If you're immobilized in a cast, for example, you can maintain some of your muscle strength by imagining contractions of the immobilized muscles. But there's a cost: last year, Canadian researchers found that visualizing a fatiguing action decreased muscular endurance in a subsequent test. Visualizing your race is a great way to prepare to achieve your goals, but dial it back in the days leading up to your race.
The longer the race, the longer you'll have to maintain your focus, so mental fatigue is a particular concern in races of 10K or longer. It's tempting to see your final-week taper as a chance to catch up on tasks that have been piling up. But the days before an important race are not the time to, say, do your taxes.
If you're traveling to a race, consider arriving an extra night early. The hassle of a Friday evening trip to a Sunday race could be worthwhile if you have all of Saturday—the most important day of your mental taper—to relax. Try to make as many decisions as possible in advance: Book a prerace dinner reservation, figure out race-day logistics, and set aside a good book to read or movie to watch (but not War and Peace). Oh, and turn off your work email. You've invested a lot of effort to get your body in peak form, so make sure your mind is just as primed to compete.