Scrambling up and down ropes and monkey bars, crawling through trenches of mud, leaping through fire—what's not to love about super extreme mud runs, especially if you're in shape and can't resist a physical and mental challenge?  

Plenty, according to a new online report from the Annals of Emergency Medicine. The report looked at the most well known mud run, the 10- to 12-mile, military-inspired Tough Mudder, which bills itself as “probably the toughest event on the planet” and attracts a quarter-million participants to its races around the country.

Report authors compiled case studies of some of the injuries participants suffered during a two-day Tough Mudder event in Pennsylvania earlier this year where 22,000 people competed. And we're not talking about your typical pulled hamstring or sore knee here (though muscle injuries were also common): 38 participants were sent to the emergency room. Injuries included electrical shocks to the head while running through water, burn marks and heart muscle inflammation from electrical injuries, partial paralysis, seizures, fainting, dehydration, and a dangerous condition linked to muscle breakdown called rhabdomyolysis. And some of the bodily harm, like paralysis, was expected to be permanent.

Tough Mudder made news earlier this year after a 28-year-old man died during a West Virginia event in April. Now, you won't get a big lecture from us on why you should never do a mud run. We just want you to know the risks—and understand that unlike a 10-K or triathlon, it's almost impossible to train for one of these down and dirty events because the obstacles aren't things you can simulate on your own, plus they're risky in general. The authors noted that endurance training could help prevent problems like dehydration and rhabdomyolysis, but even if you trained to run through a field of electrical wires, you could still get hurt doing it.

Still think these events sound crazy fun? Read up on some of the other dangers of mud runs and check out these tips on how to a mud run safely.

More from Women's Health:
When Should You Skip A Big Workout or Race?
How To Tell If Your Workout Is Too Intense
8 Things You Need to Know Before Doing a Mud Run