A charley horse refers to a muscle cramp that is sudden and painful. It often occurs during exercise and at night. It commonly affects the calf muscle at the back of the lower leg, but it can also occur in the foot and, occasionally, in the thigh.

These muscle contractions are also common during pregnancy and in people with certain health conditions. Leg cramps affect around a third of people aged over 50 years.

Cramps are common during exerciseShare on Pinterest
Cramps are common during exercise. A warm-up before starting can help to reduce the risk.

A charley horse happens when muscles suddenly cramp or tighten, resulting in pain. The condition most typically happens in the calf muscle at the back of the lower leg.

The sudden and uncontrollable spasm can often be brief, but it can last for several minutes or up to 10 minutes.

For most people, the muscle contracts painfully without lasting problems. For others, however, the cramps can be extremely painful and leave some muscle discomfort for days.

If leg cramps frequently happen at night, sleep disruption can result.

Doctors do not know exactly why muscle cramps happen when a person is exercising or when they have no other medical conditions.

However, one theory is that the charley horse or cramp may involve a nerve in a certain muscle that serves the leg.

A study published in Muscle & Nerve found that a muscle cramp involved this specific nerve. The study noted that the nerve fired at high rates of up to 150 electrical discharges every second. This high level of electrical activity forced the muscle into a tight squeeze.

Risk factors for leg cramps include:

  • pregnancy
  • older age
  • exercise
  • electrolyte imbalances or low salt levels
  • injury to a peripheral nerve or other nerve problems
  • muscle diseases
  • stroke
  • the use of certain drugs

Acute calf pain can also happen for reasons not related to cramps. These include:

A review of studies published in 2017 found that the following types of illness often occur alongside leg cramps:

Drugs and muscle cramps

Anyone who has a problem with leg cramps after taking prescription drugs may want to talk to a doctor or pharmacist, who can advise about changing the medication.

It is important not to stop taking a drug without speaking to a health professional first.

Some drugs can increase the risk of leg cramps, including:

  • Intravenous iron sucrose, such as Venofer, used for iron deficiency anemia
  • Raloxifene (Evista) and Teriparatide (Forteo), treatments for osteoporosis
  • Conjugated estrogens, which relieve the symptoms of menopause
  • Naproxen (Naprosyn), a pain relief medication
  • Levalbuterol (Xopenex) and albuterol-ipratropium (Combivent), for bronchospasm and asthma
  • Pregabalin (Lyrica), which relieves nerve pain

Other types of drug that may lead to leg cramps include statins for reducing cholesterol and diuretics for removing excess fluid from the body.

The use of some stimulants, such as amphetamines and caffeine, may increase the risk of experiencing a charley horse or leg cramp.

Anyone who notices an increase in the frequency or severity of muscle cramps should see a doctor, as they may have an underlying problem that needs addressing.

When a person visits a doctor about a charley horse problem, the doctor will more than likely ask about their symptoms, including:

  • what the cramping is like and where it occurs
  • when the cramps happen and for how long
  • how severe or regularly the cramps occur
  • whether they have started recently

A doctor is likely to ask about the person's exercise habits, diet, and any other symptoms, medical problems, or current medications, as well.

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To relieve a leg cramp, straightening the leg and pulling the foot back toward the shin may help.

There is little evidence that medical intervention can help cure or reduce muscle cramping.

However, when a muscle is cramping, and a person experiences a charley horse, the following action may help them find some relief:

  1. Gently stretch out the muscle by standing or moving the limb or foot.
  2. Firmly but gently pull the toes and the foot upward to the front of the leg.
  3. Repeat these movements until the cramping eases and stops.

Some people find that massaging the cramped muscle brings relief.

If there are signs that an underlying problem may be causing the cramps, the doctor can suggest further tests. If the person is taking a drug that increases the chance of cramping, a doctor may change this or the dosage.

Some people take quinine tablets to reduce cramping, but research has not confirmed whether this is safe or effective. Most doctors do not recommend quinine tablets because of the potential for adverse effects.

To prevent a charley horse or muscle cramp occurring, a person might try the following:

  • leaving sufficient time between eating and exercising
  • warming up before and after exercise by gently stretching muscles
  • drinking fluids and eating a little food after exercise to replace fluid and minerals
  • keeping hydrated by drinking enough water at all times
  • avoiding caffeine and other stimulants
  • monitoring any possible side effects of prescription drugs

Some people use magnesium supplements, but reviews of previous scientific studies did not find enough evidence to suggest that these help

Changes that may help, although there is no scientific evidence to support them, include:

  • relaxation, massage, and heat therapy
  • changing to different footwear
  • weight loss for people with excess weight
  • physical exercise for those with a sedentary lifestyle

It is likely that using "charley horse" to describe a muscle cramp comes from informal American sporting talk, dating back to the 1880s.

One theory is that the term comes from a baseball player who was talking about a lame horse. Horses used to help with groundskeeper jobs in baseball.

Another story, which appeared in the Washington Post in 1907, claimed that the name came from a baseball pitcher called Charley, who had muscle cramps during games in 1880.

Charley horses are not specifically related to the sport of baseball, and they can occur during any type of exercise.

A charley horse or leg cramp is a common problem and does not usually indicate a serious health problem. Nevertheless, a charley horse can sometimes result from medication or a health condition.

There is not usually any way to treat or prevent them, except perhaps to warm up before exercise and to stay well hydrated.

If a person's cramps are severe, and they experience other changes such as a changed level of consciousness or a fever, they should seek medical help.