YouTube user Andre B. from Australia uploaded this Snapchat from a friend, whose calf cramp was so extreme you can literally see the muscle moving under his skin.
The muscular horror scene is starting to go viral after being posted on Reddit.
In case it was moving too quickly for you...
The video was uploaded to Reddit by user dogzfan, where it made the front page of r/videos and received over 2,000 comments from grossed-out and mesmerized viewers.
"I was resting at home straight after exercise when suddenly my calf locked up two times, then I managed to record the last one only," he said in an email.
Buzzfeed Life reached out to Dr. Harry Pino, an exercise physiologist at the Performance Center of NYU Langone's Center for Musculoskeletal Care, to see what's really going on here.
Though he said that "muscle cramping, specifically of the calf muscle, is not fully understood," he added that there are two general types of cramps caused by certain behaviors: