A muscle cramp is an involuntarily and forcibly contracted muscle that does not relax. Almost everyone experiences a muscle cramp at some time in their life and there are a variety of types and causes of muscle cramps. Depending on the cause, muscle cramps may occur during exercise, at rest, or even at night. Dehydration is a common cause of muscle cramps, but numerous medicines can also cause muscle cramps.

The Problem

A muscle that involuntarily contracts is in a "spasm." If the spasm is forceful and sustained, it becomes a cramp. Muscle cramps often cause a visible or palpable hardening of the involved muscle. They can last anywhere from a few seconds to a quarter of an hour or occasionally longer, and it is not uncommon for a cramp to recur multiple times until it finally resolves. The cramp may involve a part of a muscle, the entire muscle, or several muscles that usually act together, such as those that flex adjacent fingers.

Muscle cramps are extremely common. Almost everyone (one estimate is about 95%) experiences a cramp at some time in their life. Muscle cramps are common in adults and become increasingly frequent with aging.