Cramps, sometimes called Charley horses, are unpleasant, often painful, sensations caused by contraction or over shortening of muscles. Cramps can be caused by cold, overexertion or low calcium level in blood (especially for adolescents where they need calcium for both blood and bone maturing). Illness or poisoning can also cause cramps, particularly in the stomach, which is referred to as colic if it fits particular characteristics.

Causes

There are six basic causes of cramping:^[1] hyperflexion; inadequate oxygenation; exposure to large changes in temperature; dehydration; low blood salt; or low blood calcium. Muscle cramps may also be a symptom/complication of pregnancy, kidney disease, thyroid disease, hypokalemia or hypocalcemia (as conditions), restless legs syndrome, varicose veins^[2], and multiple sclerosis.^[3]

Electrolyte disturbance may cause cramping and tetany of muscles, particularly hypokalaemia (a low level of potassium) and hypocalcaemia (a low level of calcium). This disturbance arises as the body loses large amounts of interstitial fluid through sweat. This interstitial fluid is composed mostly of water and table salt (NaCl). The loss of osmotically active particles outside muscle cells leads to a disturbance of the osmotic balance and swelling of muscle cells as these contain more osmotically active particles. This causes the calcium pump between the muscle lumen and sarcoplasmic reticulum to short circuit and the calcium ions remain bound to the troponin and the muscle contraction is continued. This may occur when the lactic acid is high in the cells.

Iatrogenic causes

Statins are known to cause myalgia and cramps among other side effects. Additional factors increasing probability for these adverse side effects are physical exercise, age, female gender, history of cramps and hypothyroidism. Up to 80% of athletes using statins suffer significant muscular adverse effects including cramps ^[4], the rate appears to be approximately 10-25% in typical population using statins ^[5][6]. In some cases these adverse effects will disappear after switching to a different statin, however they should not be ignored if they persist as they can rarely develop into a more serious problem. Coenzyme Q10 supplementation can be helpful to avoid some statin related adverse effects but currently there is not enough evidence to prove effectiveness in avoiding myopathy or myalgia ^[7].

Treatment

Muscle cramps can be treated by applying a soft massage on the cramped muscle, stretching your hands up above you and breathing in deeply through the mouth, stretching the muscle and applying heat or cold. Heat improves superficial blood circulation and makes muscles more flexible, so some people find that heat is more soothing for muscle cramps. Application of excessive heat or cold to sore muscles may bring on cramps. Pounding on a cramped muscle can increase soreness.

• In the case of inadequate oxygenation, excess lactic acid, produced by anaerobic respiration, builds up and stresses the muscle. In addition to the methods described above, cramps from poor oxygenation can be improved by rapid deep breathing.

• Cramps from lack of water and/or salt can be treated by drinking water and/or increasing salt intake, respectively.

There is no scientific evidence to support the widely held claim by the sports nutrition industry that intake of specially composed electrolyte drinks has any advantage over intake of plain table salt (via drink or food) and water to counter these electrolyte disturbances and muscle cramps in people with a well-functioning renal system.

Eating foods high in potassium can help prevent muscle cramps.^[8]

In the case of cramps caused by varicose veins, treatment of the affected veins with sclerotherapy, endovenous laser or surgery usually provides relief.

Quinine has been prescribed for the treatment of leg cramps. However, because of the drug's risks, the United States FDA has declared it should not be used to prevent or treat leg cramps.^[9]

Specific types of cramps

Smooth muscle cramps

Smooth muscle contractions lie at the heart of the cramping (or colicky) pain of internal organs. These include the intestine, uterus, ureter (in kidney stone pain), and various others.

Menstrual cramps

Menstruation is also highly likely to cause cramps of varying severity in the abdomen that may radiate to the lower back and thighs. Menstrual cramps can be treated with ibuprofen, acetaminophen(paracetamol), stretching exercises, or the application of heat through such means as warm baths or heating pads. Menstrual cramps that do not respond to self-treatment can be a symptom of endometriosis or other health problems.

Skeletal muscle cramps

Skeletal muscles are muscles that can be voluntarily controlled. Of the skeletal muscles, those which cramp the most often are the calves, thighs, and arches of the foot. These cramps are seemingly associated with strenuous activity and can be intensely painful.

Nocturnal leg cramps

Nocturnal leg cramps are involuntary muscle contractions that occur in the calves, soles of the feet, or other muscles in the body during the night or (less commonly) while resting. Only a few fibers of a muscle may be activated.^[10] The duration of nocturnal leg cramps is highly variable with cramps sometimes only lasting a few seconds and other times several minutes. Soreness in the muscles may remain for some time after the cramp ends. These cramps are more common in older people but may happen to anyone. They can happen quite frequently in teenagers and in some people while they are exercising at night. Nocturnal leg cramps can be very painful, especially if the person is dehydrated. Usually, putting some pressure on the affected leg by walking some distance will make the cramp go away.

The precise cause of these cramps is unclear. Potential contributing factors are believed to include dehydration, low levels of certain minerals (magnesium, potassium, calcium, and sodium), and the reduced blood flow through the muscles attendant in prolonged sitting or lying down. Less common causes include more serious conditions or the use of drugs.

Nocturnal leg cramps may be relieved by stretching the affected leg straight out and pointing the toes upward. People report that quickly standing up and walking a few steps may also shorten the duration of a cramp.

Nocturnal leg cramps (almost exclusively calf cramps) are considered to be 'normal' during the late stages of pregnancy. They can however vary in intensity from mild to incredibly painful.

See also

• Trigger points
• Side Stitch
• Delayed onset muscle soreness.

References

External links

• What are Cramps?
• Cramps at Patient UK
• Leg cramps at night
• About leg cramps
• What causes leg cramps and what to do about it
• Muscle Cramps (Of Skeletal Muscles)

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