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, and most particularly the calf (the classic “charley horse”), are very common. Skeletal muscle cramps can be categorized into four major types. These include “true” cramps, tetany, and dystonic cramps. Cramps are categorized according to their different causes and the muscle groups they affect.
Types of Muscle Cramping
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. 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: 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: Cramps at rest are very common, especially in older adults, but may be experienced at any age, including childhood. Rest cramps often occur during the 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, a common site of muscle cramps.
Dehydration: Sports and other vigorous activities 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 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.
Body fluid shifts: True cramps also may be experienced in other conditions that feature an unusual distribution of body fluids. An example is cirrhosis of the liver, which leads to the accumulation of fluid in the abdominal cavity (ascites). Similarly, cramps are a relatively frequent complication of the rapid body fluid changes that occur during dialysis for kidney failure.
Low blood calcium, magnesium: Low blood levels of either calcium or magnesium directly increase the excitability of both the nerve endings and the muscles they stimulate. This may be a predisposing factor for the spontaneous true cramps experienced by many older adults, as well as for those that are commonly noted during pregnancy.
Low potassium: Low potassium blood levels occasionally cause muscle cramps, although it is more common for low potassium to be associated with muscle weakness.
In tetany cramping, all of the nerve cells in the body are activated, which then stimulate the muscles. This reaction causes spasms or cramps throughout the body. The name tetany is derived from the effect of the tetanus toxin on the nerves. However, the name is now commonly applied to muscle cramping from other conditions, such as low blood levels of calcium and magnesium. Sometimes, tetanic cramps are indistinguishable from true cramps. The accompanying changes of sensation or other nerve functions that occurs with tetany may not be apparent because the cramp pain is masking or distracting from it.
The final category is dystonic cramps, in which muscles that are not needed for the intended movement are stimulated to contract. Muscles that are affected by this type of cramping include those that ordinarily work in the opposite direction of the intended movement, and/or others that exaggerate the movement. Some dystonic cramps usually affect small groups of muscles (eyelids, jaws, neck, larynx, etc.). The hands and arms may be affected during the performance of repetitive activities such as those associated with handwriting (writer’s cramp), typing, playing certain musical instruments, and many others. Each of these repetitive activities may also produce true cramps from muscle fatigue. Dystonic cramps are not as common as true cramps.
FAQ’s About Muscle Cramping
What are the symptoms of common muscle cramps? How are muscle cramps diagnosed?
Characteristically, a cramp is painful, often severely so. Usually, the sufferer must stop whatever activity is under way and seek relief from the cramp; the person is unable to use the affected muscle while it is cramping. Severe cramps may be associated with soreness and swelling, which can occasionally persist up to several days after the cramp has subsided. At the time of cramping, the knotted muscle will bulge, feel very firm, and may be tender.
There are no special tests for cramps. Nevertheless, the diagnosis of muscle cramps is relatively easy. Most people know what cramps are and when they have one. If present during a cramp, the doctor, or any other bystander, can feel the tense, firm bulge of the cramped muscle.
What is the treatment for skeletal muscle cramping?
Most cramps can be stopped if the muscle can be stretched. For many cramps of the feet and legs, this stretching can often be accomplished by standing up and walking around. For a calf muscle cramp, the person can stand about 2 to 2.5 feet from a wall (possibly farther for a tall person) and lean into the wall to place the forearms against the wall with the knees and back straight and the heels in contact with the floor. (It is best to learn this maneuver at a time when you don’t have the cramp.) Another technique involves flexing the ankle by pulling the toes up toward the head while still lying in bed with the leg as straight as possible. For writer’s cramp (contractures in the hand), pressing the hand on a wall with the fingers facing down will stretch the cramping finger flexor muscles.
Gently massaging the muscle will often help it to relax, as will applying warmth from a heating pad or hot soak. If the cramp is associated with fluid loss, as is often the case with vigorous physical activity, fluid and electrolyte (especially sodium and potassium) replacement is essential. Medicines generally are not needed to treat an ordinary cramp that is active since most cramps subside spontaneously before enough medicine would be absorbed to even have an effect.
Of course, if cramps are severe, frequent, persistent, respond poorly to simple treatments, or are not associated with an obvious cause, then the patient and the doctor need to consider the possibility that more intensive treatment is indicated or that the cramps are a manifestation of another disease. As described above, the possibilities are extremely varied and include problems with circulation, nerves, metabolism, hormones, medications, and nutrition. It is uncommon for muscle cramps to occur as the result of a medical condition without other obvious signs that the medical condition is present.
How can muscle cramping be prevented?
Stretching before and after exercising: Authorities recommend stretching before and after exercise or sports, along with an adequate warm-up and cool-down, to prevent cramps that are caused by vigorous physical activity. Good hydration before, during, and after the activity is important, especially if the duration exceeds one hour, and replacement of lost electrolytes (especially sodium and potassium, which are major components of perspiration) can also be helpful. Excessive fatigue, especially in warm weather, should be avoided.
Adequate hydration before, during and after exercising: Drink 0.5 liters of water per hour for several hours (three to four hours) prior to exercise. Electrolyte repletion (sodium and potassium), such as Gatorade, can help sustain electrolyte balance during exercise. Consuming beverages and snacks with sodium post exercise, such as a handful of nuts with a bottle of water, will help expedite rapid and complete recovery by stimulating thirst and fluid retention.
Prenatal vitamin during pregnancy: Supplemental calcium and magnesium have each been shown to help prevent cramps associated with pregnancy. An adequate intake of both of these minerals during pregnancy is important for this and other reasons, but supervision by a qualified health care professional is essential.
Ergonomics: Cramps that are induced by repetitive non-vigorous activities can sometimes be prevented or minimized by careful attention to ergonomic factors such as wrist supports, avoiding high heels, adjusting chair position, activity breaks, and using comfortable positions and equipment while performing the activity. Learning to avoid excessive tension while executing problem activities can help. However, cramps can remain very troublesome for activities that are difficult to modify, such as playing a musical instrument.
Stretching before bed: Night cramps and other rest cramps can often be prevented by regular stretching exercises, particularly if done before going to bed. Even the simple calf-stretching maneuver (described in the first paragraph of the section on treatment), if held for 10 to 15 seconds and repeated two or three times just before going to bed, can be a great help in preventing nocturnal cramps. The maneuver can be repeated each time you get up to go to the bathroom during the night and also once or twice during the day. If nocturnal leg cramps are severe and recurrent, a foot board can be used to simulate walking even while recumbent and may prevent awkward positioning of the feet during sleep. Ask your doctor about this remedy.