Muscle Cramp


A muscle cramp is an involuntary contraction or spasm occurring suddenly to one or more skeletal muscles. They usually occur after exercising or during the night and can last anywhere from a few seconds to several minutes.


The terms cramp and spasm are vague for most, and they are sometimes used to include types of abnormal muscle activity other than sudden painful contraction, including slow muscle relaxation, stiffness at rest, and spontaneous contractions of a muscle at rest or fasciculation. A muscle spasm is different than a muscle twitch. A muscle twitch or fasciculation is uncontrolled fine movement of a small segment of a larger muscle that can be seen under the skin. Fasciculation is a type of painless muscle spasm characterized by rapid, uncoordinated contraction of many small muscle fibers. Distinguishing the different meanings and symptoms allows the patient to describe the problem to their physician for a better diagnosis.

Types of muscle cramps

There are four types of skeletal muscle cramps: true cramps, tetany, contractures, and dystonic cramps:

Charley horse—
A common name for a muscle spasm, usually occurring in the leg.
The shortening and thickening of a functioning muscle or muscle fiber.
A tightening or shortening of muscles that prevents normal movement of the associated limb or other body part.
Excessive loss of water from the body or from an organ or body part, as from illness or fluid deprivation.
The ionized salts present in body fluids that play an important role in functioning of the human body. Electrolyte levels in blood plasma and urine are often used as diagnostic tools.
Involuntary contractions or twitchings of groups of muscle fibers. Fasciculations can occur in normal individuals without an associated disease or condition and can also occur as a result of illness, such as muscle cramps, nerve diseases, and metabolism imbalances.
Motor neuron—
A nerve cell that specifically controls and stimulates voluntary muscles.
Muscle spasm—
Localized muscle contraction that occurs when the brain signals the muscle to contract.
The inability to normally relax a muscle after contracting or tightening it.
Nocturnal leg cramps—
Cramps that may be related to exertion and awaken a person during sleep.


Some people are predisposed to muscle cramps and get them regularly with physical exertion. Those at greatest risk for cramps and other ailments related to excess heat include infants; young children; people over age 65; and those who are ill, overweight, over-exert during work or exercise, or take drugs or certain medications.

Muscle cramps are very common among endurance athletes, including marathon runners and triath-letes, as well as older people who perform strenuous physical activities. Athletes are more likely to get cramps in the preseason when the body is not conditioned and, therefore, more subject to fatigue. Cramps often develop near the end of intense or prolonged exercise, or four to six hours later. Older people are more susceptible to muscle cramps due to normal muscle loss (atrophy) that begins in the mid-40s and accelerates with inactivity. As the body ages, muscles cannot work as hard or as quickly as they used to. The body also loses some of its sense of thirst and its ability to sense and respond to changes in temperature.

Causes and symptoms

Although the exact cause of muscle cramps is unknown, some researchers believe inadequate stretching and muscle fatigue leads to abnormalities in mechanisms that control muscle contraction. Other factors may also be involved, including poor conditioning, exercising, or working in intense heat.

Muscle cramps can be caused by the overuse of a muscle, dehydration, pregnancy, heavy exercise, muscle strain, a lack of minerals in the diet or the depletion of salt and minerals in the body, not enough blood getting to the muscles, or simply holding the same position for an extended period of time. They can also be caused by a sudden involuntary contraction of a muscle or muscles. It is uncommon for cramps to be due to a serious underlying disorder. In most cases, the cramp goes away within a few minutes. Some rare causes of muscle cramps are drugs such as lithium, alcohol, and inflammatory disorders such as polymyositis and tetanus. Muscle cramps are also part of certain conditions such as nerve, kidney, thyroid or hormone disorders; diabetes; hypoglycemia; and anemia.

Symptoms of muscle cramps include intense, localized, and often debilitating pain that comes on quickly and may last for seconds or minutes, fading gradually. Another symptom is a hard lump of muscle tissue that can be felt or is visible beneath the skin. Contractures develop more slowly, over days or weeks, and may be permanent if untreated. Fasciculation may occur at rest or after muscle contraction and may last several minutes.


Muscle cramps may accompany other symptoms that vary depending on the underlying disease, disorder or condition. Symptoms that frequently affect the muscles may also involve other body systems. Exercising in high temperatures can lead to dehydration, another symptom of muscle cramps. Dehydration symptoms include dry mouth or tongue, increased or excessive thirst, few or no tears when crying, decreased urination, dark yellow urine, irritability, low energy, lightheadedness or fainting, severe weakness, and sunken abdomen, eyes and cheeks. Muscle cramps may accompany other symptoms affecting the muscle including, burning feeling, lump in the cramping muscle, muscle pain that may be severe and sharp, muscle weakness, and twitching.


A usual bout of muscle cramps should not require a visit to the doctor. However, medical treatment is essential if any symptoms of dehydration are associated with the muscle cramps. In addition, any abnormal contractions or frequent muscle cramps or spasms that cause concern should be evaluated by a physician. Abnormal muscle contractions are diagnosed through a careful medical history, as well as a physical and neurological examination. In some cases, when a structural abnormality is suspected, x-rays may be performed. The medical history helps the physician to evaluate the presence of other conditions or disorders that might contribute to or cause the abnormal contractions. Records of previous diagnoses, surgeries, and treatments will also be reviewed. The family medical history is evaluated to determine if there is a history of muscular or neurological disorders.


Most cases of simple cramps require no treatment other than patience and stretching. When heat cramps occur, stop the activity, move to a cool or shady place, remove excess clothing, drink cool water or a sports drink with electrolytes such as Gatorade, and rest. If nausea or dizziness occur, lie down, with feet slightly elevated. Gently and gradually stretching and massaging the affected muscle may ease the pain and hasten recovery. Briefly applying cold packs to cramped muscles, for about ten minutes, may also help ease pain. Acetaminophen (such as Tylenol) or ibuprofen (such as Advil or Motrin) should be used sparingly for relief of discomfort. If prolonged or recurrent cramps that disturb sleep occur, medication to relax the muscles can be prescribed by a doctor.

Cramps may be treated or prevented with gingko (Ginkgo biloba) or Japanese quince (Chaenomeles speciosa). Supplements of vitamin B12, folate, vitamin E, niacin, calcium, and magnesium may also help. Taken at bedtime, they may help to reduce the likelihood of night cramps.


In most cases, muscle cramps are relatively mild and resolve within a few minutes. Despite being a temporary discomfort, they are a benign condition. Their importance is limited to the discomfort and inconvenience they cause, or to the diseases associated with them. Careful attention to them will greatly diminish the problem of cramps for most individuals. Those with persistent or severe muscle cramps should seek medical attention.


The best way to prevent muscle cramps is avoiding dehydration by drinking plenty of liquids daily. The exact amount will depend on an individual's diet, sex, level of activity, the weather, health, age, and any medications currently being taken. Fluids help muscles contract and relax and keep muscle cells hydrated and less irritable. Fluids should be replenished after physical activity. Stretching muscles before and after use is another way to prevent muscle cramps. If cramps occur at night, stretch before bedtime. Stretching is recommended before and after for cramps that are caused by vigorous physical activity. An adequate warm up and cool down before and after activity can help prevent muscle cramps. Adequate hydration before, during, and after physical activity is important, especially if the duration exceeds one hour, and replacement of electrolytes (especially sodium and potassium, which are major components of perspiration) can also be helpful. Excessive fatigue, especially in warm weather, should be avoided. Supplemental calcium and magnesium have each been shown to help prevent cramps associated with pregnancy. Drinking water before bedtime can also alleviate night cramps.



Brinker, M.R., et al. “Basic Science and Injury of Muscle, Tendon, and Ligament.” In DeLee and Drez's Orthopaedic Sports Medicine, 4th ed., edited by J.C. DeLee, D. Drez Jr., and M.D. Miller. Philadelphia: Saunders Elsevier; 2014.

Fauci, Anthony S., et al. Harrison's Principles of Internal Medicine, 19th ed. New York: McGraw-Hill Professional, 2015.

Filho, J.A.F., and A. Pestronk. “Chapter 28: Muscle Pain and Cramps.” In Neurology in Clinical Practice, 7th ed., edited by Walter G. Bradley, et al. Philadelphia: Butterworth-Heinemann, 2015.


Schwellmus, M.P. “Muscle Cramping in Athletes: Risk Factors, Clinical Assessment, and Management.” Clinics in Sports Medicine 27 (2008): 183.


American Academy of Orthopaedic Surgeons, 9400 W Higgins Rd., Rosemont, IL, 60018, (847) 823-7186, (800) 626-6726, Fax: (847) 823-8125,, .

National Institute of Arthritis and Musculoskeletal and Skin Diseases, 1 AMS Circle, Bethesda, MD, 20892, (301) 495-4484, (877) 22-NIAMS (226-4267), Fax: (301) 718-6366,, .

Karl Finley

  This information is not a tool for self-diagnosis or a substitute for professional care.