When it comes to fitness, caffeine stimulates the nervous system in ways that activate your muscles more quickly, increase your ability to use fat as fuel, and make long runs feel easier, says Dan Daly, Tier X coach at Columbus Circle in New York City who has a Precision Nutrition level 2 certification.
If caffeine is a daily habit, your brain builds up a tolerance for the chemical, dulling its effects on race morning—and in general.
The bottom line:
Forego all caffeine for at least two and ideally seven days before a race to get extra benefits, Daly says. Research shows that no matter how much you typically drink, your sensitivity resets after one decaf week.