If you’ve ever woken up in the middle of the night with a charley horse – a.k.a muscle spasm – then you know what a pain these leg cramps can be.

Charley horse is a colloquial term for a sudden, intense muscle contraction that often occurs in the calf, thigh or foot during sleep. More than half of adults report they have experienced these spasms at night, which can last anywhere from a few seconds to several excruciating minutes. 

“Even if it’s only 10 seconds, it feels like 20 years until it goes away,” Nicole Haas, a physical therapist told HuffPost. 

Charley horses can also happen while you’re awake (like during or after exercise), and in other parts of the body, but here we’ll be focusing on the nocturnal variety. We talked to an orthopaedic surgeon and two physical therapists to learn more about the dreaded, middle-of-the-night charley horse. 

What causes charley horses?

It’s not entirely understood what causes charley horses, though a number of factors could be at work.

For many years, experts believed muscle cramping was linked to dehydration and a loss of electrolytes (which creates an imbalance of minerals like magnesium and potassium in the body), though research now suggests it may have more to do with muscle fatigue and nerve dysfunction.

“It is believed that such muscle contractions are due to involuntary repetitive firing of the nerve rather than originating from within the muscle itself,” said Nabil Ebraheim, chair of the department of orthopaedic surgery at the University of Toledo Medical Center. “The most common cause is straining or overusing the muscle.” 

Other factors that may increase the likelihood of muscle cramping include long periods of sitting or standing, poor circulation, certain medications like diuretics, a sedentary lifestyle and exercise without proper stretching. Pregnant women, athletes, older adults and people who are overweight may be especially prone to such cramps. 

Why they happen at night

It’s also not totally clear why charley horses often happen during sleep, but experts have some theories. 

“At the end of the day, fatigue of the muscles due to poor posture, prolonged sitting or inefficient biomechanics during exercises can create the tightness or spasm,” said Jonathan Meltzer, a physical therapist at Rausch Physical Therapy in Laguna Niguel, California. 

Also, consider how your body is positioned during sleep, as it could be encouraging cramping. If you’re sleeping on your back and your feet are pointed downward — known as “plantar flexion” — for a long time, it can cause a tightness in your calf muscle, Haas said. Same goes for those who sleep on their stomachs. 

“I see that a lot when winter starts to roll in and the heavy covers come out,” Haas said. “When you point your toes, you’re using your calf. But if you have your toes held down, like by a heavy blanket, you’re also in a shortened position of your calf muscle.”

How to prevent charley horses

There are a few ways you can prevent and ease the pain of charley horses, according to the experts. They recommend:

• Incorporating good habits, like stretching, foam-rolling or using a muscle roller stick to loosen tight muscles. “Muscles need to be stretched regularly to function properly,” Ebraheim said. “Stretch before going to bed, particularly the calves and feet.”

• Staying active, but not to the point of overexertion. Regularly change positions throughout the day so you’re not seated or standing for too long. “Adjust posture on a regular basis at work and home,” Meltzer said. “Sitting is not bad, but for a prolonged period of time it is. Make sure on the hour you stand up, walk around and focus on an upright sitting posture.” 

• Though research on the link between hydration and muscle cramps is mixed, there are really no downsides to making sure you’re drinking enough water. “We don’t know for sure that it helps, but it definitely can’t hurt,” Haas said.

• Adjust your sleeping position. If you like sleeping on your back with a comforter, Haas recommends rolling up a towel at the end of the bed to create a little canopy of space over your feet. You can also rest the bottom of your feet against the towel, so your feet never go all the way into a pointed position. Another option? Sleep on your side. 

How to relieve the pain if you get a nighttime cramp

You probably can’t stop a charley horse in its tracks once it starts. However, you may be able to reduce the duration of pain. 

When people get a charley horse, they often lay there frozen ― and, if you’re me, on the verge of shouting an expletive ― not knowing what the heck to do.

• Next time it happens, try flexing your foot (i.e. pull toes toward your body, not away from it) to get some relief. “If you get a little tension in the calf muscle, that will hopefully get it to release and let go,” Haas said. “If that’s not enough, some people do need to stand up to do a calf stretch. I think it’s helpful to have toes up on something if you can, even if it’s a book or a towel rolled up.”

• Afterward, you may experience some residual soreness in the muscle. You can try a heating pad, a massage or ice to ease the pain, Ebraheim said. If the pain persists, ibuprofen may help. 

The occasional charley horse is unpleasant, but pretty harmless. However, if they’re happening frequently, tell your doctor to rule out the possibility of a more serious health issue.