Muscle cramps facts
- A muscle cramp is an involuntarily and forcibly contracted muscle that does not relax.
- Muscle cramps can occur in any muscle; cramps of the leg muscles and feet are particularly common.
- Almost everyone experiences a muscle cramp at some time in their life.
- There are a variety of types and causes of muscle cramps.
- Muscle cramps may occur during exercise, at rest, or at night, depending upon the exact cause.
- Dehydration is a common cause of muscle cramps.
- Numerous medicines can cause muscle cramps.
- Most muscle cramps can be stopped if the muscle can be stretched.
- Muscle cramps can often be prevented by measures such as adequate nutrition and hydration, attention to safety when exercising, and attention to ergonomic factors.
Muscle Cramps: a Real Pain
Cramps can be perceived as mild twitches or may be excruciatingly painful. Typically, cramps cause an abrupt, intense pain in the involved muscle.
Often a muscle that is cramping feels harder than normal to the touch or may even show visible signs of twitching.
What are muscle cramps?
A muscle cramp is an involuntarily and forcibly contracted muscle that does not relax. When we use the muscles that can be controlled voluntarily, such as those of our arms and legs, they alternately contract and relax as we move our limbs. Muscles that support our head, neck, and trunk contract similarly in a synchronized fashion to maintain our posture. A muscle (or even a few fibers of a muscle) that involuntarily (without consciously willing it) 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.
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 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. Some cramps involve the simultaneous contraction of muscles that ordinarily move body parts in opposite directions.
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. However, children also experience cramps of muscles.
Any of the muscles that are under our voluntary control (skeletal muscles) can cramp. Cramps of the extremities, especially the legs and feet (including nocturnal leg cramps), and most particularly the calf (the classic “charley horse”), are very common. Involuntary muscles of the various organs (uterus, blood vessel wall, bowels, bile and urine passages, bronchial tree, etc.) are also subject to cramps. Cramps of the involuntary muscles will not be further considered in this review. This article focuses on cramps of skeletal muscle.
What are the types and causes of muscle cramps?
Skeletal muscle cramps can be categorized into four major types. These include “true” cramps, tetany, contractures, and dystonic cramps. Cramps are categorized according to their different causes and the muscle groups they affect.
Types of muscle cramps: True cramps
True cramps involve part or all of a single muscle or a group of muscles that generally act together, such as the muscles that flex several adjacent fingers or the leg muscles. Most authorities agree that true cramps are caused by hyperexcitability of the nerves that stimulate the muscles. They are overwhelmingly the most common type of skeletal muscle cramps. True cramps can occur in a variety of circumstances as follows.
Injury and vigorous activity muscle cramps
Injury: Persistent muscle spasm may occur as a protective mechanism following an injury, such as a broken bone. In this instance, the spasm tends to minimize movement and stabilize the area of injury. Injury of the muscle alone may cause the muscle to spasm.
Vigorous activity: True cramps are commonly associated with the vigorous use of muscles and muscle fatigue (in sports or with unaccustomed activities). Such cramps may come during the activity or later, sometimes many hours later. Likewise, muscle fatigue from sitting or lying for an extended period in an awkward position or any repetitive use can cause cramps. Older adults are at risk for cramps when performing vigorous or strenuous physical activities.
Rest cramps and dehydration muscle cramps
Rest cramps: Cramps at rest are very common, especially in older adults, but may be experienced at any age, including childhood. Rest muscle cramps often occur at night. While not life threatening, night cramps (commonly known as nocturnal cramps) can be painful, disruptive of sleep, and they can recur frequently (that is, many times a night, and/or many nights each week). The actual cause of night cramps is unknown. Sometimes, such cramps are initiated by making a movement that shortens the muscle. An example is pointing the toe down while lying in bed, which shortens the calf muscle of the leg, a common site of muscle cramps.
Dehydration: Sports and other vigorous activities, including activities of endurance athletes, can cause excessive fluid loss from perspiration. This kind of dehydration increases the likelihood of true cramps. These cramps are more likely to occur in warm weather and can be an early sign of heat stroke. Chronic volume depletion of body fluids from diuretics (medicine that promote urination) and poor fluid intake both lead to dehydration and may act similarly to predispose to cramps, especially in older people. Sodium depletion has also been associated with cramps. Loss of sodium, the most abundant chemical constituent of body fluids outside the cell, is usually a function of dehydration.