Cramps, sometimes called Charley horses, are very 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: 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, and multiple sclerosis.Muscle Cramps at WebMD

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 , the rate appears to be approximately 10-25% in typical population using statins . 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 .

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. Trying to put weight on a cramp too soon can cause another cramp, or even a temporary loss of ability to use that muscle.