Cramps are unpleasant, often painful sensations caused by muscle contraction or over shortening. Common causes of skeletal muscle cramps include muscle fatigue, low sodium, and low potassium. Smooth muscle cramps may be due to menstruation or gastroenteritis. Causes of cramping include hyperflexion, hypoxia, exposure to large changes in temperature, dehydration, or low blood salt. Muscle cramps may also be a symptom or complication of pregnancy, kidney disease, thyroid disease, hypokalemia, hypomagnesemia or hypocalcemia (as conditions), restless-leg syndrome, varicose veins, and multiple sclerosis. Electrolyte disturbance may cause cramping and muscle tetany, particularly hypokalaemia and hypocalcaemia. This disturbance arises as the body loses large amounts of interstitial fluid through sweat. This interstitial fluid comprises mostly water and table salt (sodium chloride).
Contributions by Verdatum, 22.214.171.124, and 126.96.36.199.