A
cramp is a sudden, and involuntary
muscle contraction or over-shortening; while generally temporary and non-damaging, they can cause mild-to-excruciating
pain, and a
paralysis-like immobility of the affected muscle(s). Onset is usually sudden, and it resolves on its own over a period of several seconds, minutes, or hours. Cramps may occur in a
skeletal muscle or
smooth muscle. Skeletal muscle cramps may be caused by any combination of
muscle fatigue, a lack of
electrolytes (e.g.,
low sodium,
low potassium, or
low magnesium). Cramps of smooth muscle may be due to
menstruation or
gastroenteritis.