If you've ever suffered a leg cramp, you know how painful and unpredictable it can be. Well this dude is recorded having a leg cramp of all leg cramps.
First thing that pop to mind when watching this dude's muscle contractions is that he has some sort of parasite that it about to burst out of him like that thing from Alien. But then again this dude is pretty jacked so it's probably just that you can see the cramp in a lot more detail.