Alyssa Thorne
March 31, 2017 4:00 pm
Cultura RM Exclusive/Frank and Helena/ Getty Images

When we think of people who run marathons on the reg, we think of some of the healthiest people we know. But this might not be true — turns out, running a marathon is as traumatic as having gone through a recent heart surgery.

According to a new study, 80% of runners who do marathons end up with kidney function similar to patients fresh out of heart surgery or barely making it in the ICU. Marathoner’s kidneys weren’t permanently damaged, but still. Woah.

Blood and urine samples collected during this study from runners after a marathon had similar results to patients suffering from acute kidney injuries.

It’s suggested that this happens for a number of reasons. You inevitably become dehydrated during a marathon, which messes with your kidneys — which is the primary “traumatized” part of your body in these studies. Running also raises your body temp which further stresses your body out.

Luckily, your body chemistry DOES go back to normal a few days after running a marathon. So the takeaway isn’t so much “don’t run a marathon” as “respect your body and give it time to rest.”

Although, y’know. For those of us who think of distance running as a circle of hell, this isn’t a bad excuse to stick to other workouts, or to cheer on your friends next time they ask you to run a marathon with them. Your kidneys will thank you.