Do intense workouts make you more likely to get sick?

Whether it’s a long run day during your marathon training, or if you push yourself to the absolute limit during an Orangetheory class, there’s a definite hurts-so-good feeling that inevitably takes over after an intense workout. With nothing left in the tank, you’re spent. Researchers have long believed that this feeling weakens the body’s immune system, making it less able to fight off potential sicknesses. But according to the New York Times, it turns out strenuous exercise could actually be just as effective as preventive medicine.

In a study highlighted in the recent issue of the journal Frontiers in Immunology, researchers dyed the immune cells in mice to track their volume and whereabouts before, during, and after making the animals run around. They saw that as the mice “worked out,” their immune cells flooded the blood system and then were dispersed in the body to their lungs, gut, bone marrow, and other places. In other words, after intense activity, the body is primed to fight infection of all kinds.

“People should not be put off exercising for fear of it suppressing their immune system. Exercise is good for the immune system.” — John Campbell, PhD

“People should not be put off exercising for fear of it suppressing their immune system. Exercise is good for the immune system,” says the study’s co-author John Campbell, PhD, who is a professor at the University of Bath. While it’s important to keep in mind that similar studies where immune cells are dyed and tracked haven’t been conducted on humans, it still offers up some pretty interesting insight.

It all points to this idea: Work out hard, refuel properly, and foam-roll it out, and your body will be primed to protect you—not worn down.

Here’s what to eat when you are sick. Plus, other ways to give your immune system a boost.