EL MONTE, CALIFORNIA — A California man’s post-gym downtime turned horrifying fast, after his leg began spasming intensely.

Angel Bermudez wrote on Facebook that he was sitting in his car when the painful cramps started. He went on to film the ordeal, which lasted at least 50 seconds, and put it up online, where it has since gotten at least 14 million views.

Muscle cramping is a common issue with people who work out or play sports. But what exactly causes it?

According to Scientific American, skeletal muscles like those in the leg and arms move in response to signals from the brain. If this process malfunctions or becomes hyperactive, it can lead to painful and prolonged contractions, otherwise known as muscle cramps.

Cramps are sometimes caused by muscle strain, either by overusing a particular muscle or holding a position for too long.

Other factors that may contribute to cramping are heat, dehydration, and electrolyte imbalance.

Experts suggest stretching both as a way to soothe cramps and as a means to prevent them.

Individuals are also advised to keep hydrated and replenish their electrolytes when doing any strenuous activity.