Watching This Calf Cramp in Action Is Equally Horrifying and Mesmerizing

But this wasn’t the case for Angel Bermudez, a fitness enthusiast who documented his calf cramp on Facebook to show the extent to which his body curled and moved on its own. More than just a stiffened, flexed muscle, you can actually watch the man’s calf twitch in the 15-second clip.

“I’m not doing anything,” Bermudez says in the video. If this doesn’t make your skin crawl, too, we aren’t sure what will.

Why did his muscles react in such a way? You’ve probably felt a few cramps that were extremely painful, but they didn’t look this wild on the outside. Turns out, though, that this visible cramping where the muscles ball up, tick or twitch isn’t an uncommon circumstance. It just depends on your body.

“Being able to see a cramp is a result of the amount of muscles cramping at once, how deep the cramping muscles are, and whether there is fat over them,” Nadya Swedan, M.D., a physical medicine and rehabilitation specialist for sports injuries based in New York City, tells SELF. “Because cramping is an involuntary, irregular muscle spasm it does not recruit an entire muscle in a normal way.”

As for why some people experience these jaw-dropping, extreme spasms, there are plenty of potential factors.

“Cramping is not fully understood in the medical field, but an imbalance in nutrients including potassium, calcium, and magnesium is associated with cramping,” says Dr. Swedan. And this would be why you’ve often been told to eat a banana after a tough workout.

Other possible culprits behind these intense cramps could be sweating in hot weather, dehydration from extreme temperatures and, of course, over-training your body with a lack of proper stretching.