A cramp is a sudden, involuntary, painful skeletal muscle contraction or overshortening associated with electrical activity. While generally temporary and non-damaging, they can cause significant pain and a paralysis-like immobility of the affected muscle. A cramp usually goes away on its own over several seconds or (sometimes) minutes. Cramps are common and tend to occur at rest, usually at night. They are also often associated with pregnancy, physical exercise or overexertion, and age ; in such cases, cramps are called idiopathic because there is no underlying pathology. In addition to those benign conditions, cramps are also associated with many pathological conditions.