You’re finally asleep after a tough day when, all of a sudden, your left calf recoils in a pain so intense you’re seeing stars. A charley horse has seized your limb, and you’re now wide awake — and in agony.

These involuntary spasms come out of nowhere and ball up the muscles, typically in the calf. They can last for seconds or minutes, and several hours of soreness usually follow.

You’re hardly alone in your pain: According to the American Academy of Family Physicians, about 60% of people in the U.S. report having charley horses. But what causes them and how can you keep from getting them?

There have been many studies, but researchers can point to no specific trigger. It could be dehydration or an electrolyte imbalance, possibly flat feet or circulation problems. Prolonged sitting could be the reason, or standing too long on a concrete floor. Or they could be a sign of a neurological disorder, neuropathy or even Parkinson’s disease.

Of course, when you’re wincing in pain, all you care about is relief, now!

First, stretch the affected leg and point your toes toward your head. Once the spasm has eased, consider taking a hot bath or a cold shower. Drink plenty of water or gulp down some pickle juice. One study found that drinking pickle juice reduces cramps 40% faster than drinking water.

To keep ol’ charley at bay, stretch your leg muscles every day. Stay hydrated and keep the bed covers loose around your feet. If the cramps keep coming back, tell your doctor. You may need a mineral supplement.

Follow these steps and you may be able to get rid of charley — and the horse he rode in on, too.