What Is a Muscle Cramp?
As we normally use our muscles, they alternately contract and relax as we move our limbs back and forth. Similarly, the muscles that maintain our posture contract and relax in a synchronized fashion. A muscle that involuntarily contracts without our consciously willing it is called a "spasm." If the spasm is forceful and sustained, it becomes a cramp. A muscle cramp is an involuntarily and forcibly contracted muscle that does not relax. Muscle cramps cause a visible or palpable hardening of the involved muscle.
Muscle cramps can last anywhere from a few seconds to a quarter of an hour or occasionally longer. It is not uncommon for a cramp to recur multiple times until it finally goes away. 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. Some cramps involve the simultaneous contraction of muscles that ordinarily move body parts in opposite directions.
Muscle cramps are extremely common, and nearly everyone experiences a cramp at some time in their life. Cramps are common in adults and become increasingly frequent with aging. However, children also experience cramps.
Any of the muscles that are under our voluntary control (skeletal muscles) can cramp. Cramps of the extremities, especially the legs and feet, and most particularly the calf (the classic "charley horse"), are very common. Involuntary muscles, those we cannot control, of the various organs (heart, uterus, blood vessel wall, intestinal tract, bile and urine passages, bronchial tree, etc.) are also subject to spasms and cramps but will not be further considered in this review. This article focuses on cramps of the muscles that move joints, the muscles we can consciously control, the voluntary muscle known as skeletal muscle.
Medically Reviewed by a Doctor on 7/26/2016
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