You're not just imagining things: Doctors often refer to the 72 hours after an intense fitness event (like a marathon, ultra, or long-distance triathlon) as the "open window" for infection, says Nate Jones, MD, sports medicine physician at Loyola University Medical Center. And yes, you're more likely to get sick during this time—especially if you don't take precautions. Here's why, and what you can do about it.
Why You Get Sick
Exercise, in moderate doses, increases immunity. The body reacts to stress from exercise similarly to the way it reacts to an infection, and your immune system gets a slight boost from the stimulus. But when you cross the line into endurance exercise and really long or hard workouts, it starts to work in the other direction, explains Jones. During intense bouts of fitness, the body is flooded with stress hormones (like cortisol) and the immune system reacts by kicking into defensive gear. Once you cross the finish line that protective immune response decrease more rapidly than the stress hormones making you more vulnerable to viruses and bacteria.
And chances are, there are plenty of those around. "Think about the end of a race," says Jones. "Hundreds of sweaty people hugging, blowing their noses, grabbing at the free food—there's a ton of exposure."
Add that to the fact that many athletes celebrate with a few beers and often have to travel shortly after their races—all in that "open window"—and you've got a perfect venue for easily-transmittable viruses to take hold.
Protect Yourself: Before
Paying attention to your nutrition and hydration in the weeks and days leading up to your race can help diminish some of that post-race decreased immunity, recommends Jones. "Some people don't eat enough, especially if they're trying to get down to race weight. But getting enough carbs and protein, and enough calories in general, will protect you."
Resting between hard workouts is also important, because it gives your body time to recover and keeps stress hormones (and your immune system) from going into overdrive as you ramp up your training.
Protect Yourself: During
Feeling worn down is inevitable after a long endurance event, but you may be able to avoid feeling worse by staying hydrated during your race. In fact, a 2007 study found that drinking carbohydrate beverages (like a sports drinks) during a race can reduce the production of stress hormones.
Drinking fluids can also keep your mouth and throat from getting too dry (especially if you breathe through your mouth) and help prevent irritation, soreness, and potentially, infection.
Protect Yourself: After
Once your race is over, avoid touching your face (and other people) as much as possible. "If you can pack some alcohol-based sanitizer in your bag, you may be able to at least clean your hands fairly quickly after the race," says Jones.
Drink plenty of fluids and load up on carbs—not the beer kind—immediately afterward, as well. One worth trying? Tart cherry juice. A recent study found that runners who sipped the antioxidant-rich beverage for five days before, the day of, and two days after a marathon had lower levels of inflammation in their blood 24 and 48 hours post-race. None of the cherry juice drinkers developed upper-respiratory symptoms, while 50 percent of those in the placebo group did.
Jones also encourages his athletes to get lots of antioxidants in their diet, but the research is still out on whether this actually makes a big difference.
In a 2012 review of previous studies on the subject, Austrian researchers concluded that there's still much we don't know about how nutrition affects an athlete's immunity. "The ultimate goal of future research is to create a sports drink that contains carbohydrate and a cocktail of immunomodulatory supplements that attenuate markers of inflammation and reduce the risk of infection," they wrote in the paper.
Until then, says Jones, use common sense and practice healthy habits: Wash your hands, get plenty of rest, eat a balanced diet, and lay low during that open window of vulnerability. The better you take care of yourself after a race, the sooner you’ll be back out there training for the next one.