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 can also occur in the foot and, occasionally, the thigh.

These muscle contractions may also affect pregnant people and individuals with certain health conditions. Leg cramps affect around a third of people aged over 50 years.

As a 2021 review explains, doctors do not know exactly why muscle cramps occur. This is partly because muscle cramps can arise for a variety of reasons.

Possible causes of muscle cramps include the following:

  • Nocturnal leg cramps may have their origins in strenuous daytime activity, perhaps along with electrolyte imbalances and the use of some medications.
  • Weight gain, blood flow disruption, and peripheral nerve compression may cause muscle cramps during pregnancy.
  • Neurological changes, dehydration, and electrolyte imbalances may cause cramps during or after exercise, especially in the arms or legs.

Charley horse is another term for cramps, especially those that affect the leg.

Although some people may use charley horse to describe muscle spasms or twitches, these phenomena are very different.

Generally speaking, doctors recognize the importance of distinguishing between cramps and similar-seeming conditions, such as:

  • dystonia, a movement disorder involving involuntary movements
  • myotonia, the process of muscles tensing, including both voluntarily flexing and involuntary contracting
  • tetany, an electrolyte imbalance due to low levels of calcium
  • myalgia, or muscle aches

Scientists understand that a charley horse occurs 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 is often brief, but it can last up to 10 minutes.

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

A cramp can have different effects depending on its location. Painful leg cramps can make it more difficult to walk, for instance.

Stomach cramps, by contrast, can lead to feelings of discomfort, which may dissuade some people from eating.

Additionally, a cramp’s timing can affect its significance. For example, if leg cramps frequently happen at night, sleep disruption can result.

As a 2021 review explains, there are several risk factors for leg cramps:

  • Being over 60: Nocturnal leg cramps affect around 37% of Americans over 60 years of age.
  • Being pregnant: Muscle cramps affect around 50% of pregnant individuals, especially at night.
  • Having chronic renal failure: Around 50% of people with chronic renal failure experience muscle cramps, especially in the legs.
  • Having amyotrophic lateral sclerosis (ALS): People with ALS have a 95% chance of experiencing muscle cramps.
  • Having diabetes: Around 60% of people with type 1 diabetes have muscle cramps. In people with type 2 diabetes, the number is around 80%.

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

Some drugs can increase the risk of leg cramps. These include statins, which help lower cholesterol, and diuretics, which help with high blood pressure.

The use of some stimulants, such as amphetamines and caffeine, could also lead to a charley horse or leg cramp.

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

However, it is also important not to stop taking a drug without speaking to a health professional first.

Anyone who notices an increase in the frequency or severity of muscle cramps should contact 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 may ask about their symptoms, including:

  • what the cramping is like and where it occurs
  • when the cramps happen, how often, and for how long
  • how severe the cramps are
  • whether they have started recently
  • what the person’s exercise habits are like
  • whether the person has other symptoms, medical problems, or is on any medication

As the 2021 review explains, a doctor may also ask the person to perform stretches around the area affected by cramps or move nearby muscles. This can help the doctor determine the potential cause.

Research suggests that the only medication that can help reduce the intensity and frequency of leg cramps is quinine.

However, doctors do not like to recommend this drug, as its efficacy is uncertain despite its potential for serious side effects.

When 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, a 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.

To prevent a charley horse or muscle cramp from 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 in an effort to alleviate cramps. However, research suggests that magnesium supplements do not help with either leg cramps in pregnancy or nocturnal legs cramps.

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

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

Although the origin of the term is uncertain, sources indicate that using the term 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 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 baseball and can occur during any 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 a medication or health condition.

There is usually no way to treat or prevent a charley horse, except perhaps to warm up before exercise and stay well hydrated.

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