Muscle Cramps : When we use the muscles that can voluntarily be controlled, 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 called a "spasm." If the spasm is forceful and sustained, it becomes a cramp. A muscle cramp is thus defined as an involuntarily and forcibly contracted muscle that does not relax. Muscle cramps can last anywhere from a few seconds to a quarter of an hour, and 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. Cramps are extremely common. Almost 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 of the various organs (uterus, blood vessel wall, intestinal tract, 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.

How can muscle cramps be prevented : Activity. For cramps that are caused by vigorous physical activity, authorities recommend stretching before and after the activity, along with an adequate warm-up and cool down. Good hydration before, during, and after the activity is important, as well as replacement of lost electrolytes (especially sodium and potassium, which are major components of perspiration). Excessive fatigue, especially in warm weather, should be avoided. 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 professional is essential. Dystonic cramps. 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. Rest Cramps. 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 will often be a great help in preventing cramps, usually within a week or two. The maneuver can be repeated each time the person gets up to go to the bathroom during the night, and also during the day once or twice. It may also help to avoid flexing the foot and pointing one's toes while in bed. If nocturnal leg cramps are severe and recurrent, a foot board allows the sufferer to simulate walking even while recumbent, and may prevent awkward positioning of the feet during sleep. Another important aspect of prevention of night cramps is adequate calcium and magnesium. Blood levels may not be sufficiently sensitive to accurately reflect what is actually happening at the tissue surfaces where the hyperexcitability of the nerve is occurs. Calcium intake of at least 1 gram daily is reasonable, and 1.5 grams may be appropriate, particularly for women with osteoporosis. An extra dose of calcium at bedtime may help prevent cramps. Supplemental magnesium may be very beneficial for some, particularly if the person has a magnesium deficiency. However, added magnesium can be very hazardous for persons who have difficulty eliminating magnesium, as happens with kidney insufficiency.

Common Causes of Cramps : Numerous medicines can cause cramps. Potent diuretic medications, such as furosemide (Lasix), or the vigorous removal of body fluids even with less potent diuretics can induce cramps by depleting body fluid and sodium. Simultaneously, diuretics often cause the loss of potassium, calcium, and magnesium, which can also cause cramps. Several vitamin deficiency states may directly or indirectly lead to muscle cramps. These include deficiencies of thiamine (B1), pantothenic acid (B5), and pyridoxine (B6). Poor circulation to the legs, which results in inadequate oxygen to the muscle tissue, can cause severe pain in the muscle. This commonly occurs in the calf muscles. While the pain feels virtually identical to that of a severely cramped muscle, the pain does not seem to be a result of the actual muscle cramping. This pain may be due to accumulation of lactic acid and other chemicals in the muscle tissues.

Types of Cramps : There are four major types of skeletal muscle cramps according to McGee (1). These include "true" cramps, tetany, contractures, and dystonic cramps. Cramps are categorized according to their different causes and the muscle groups they affect. "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. 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. Tetany : In tetany, 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. Low calcium and low magnesium, which increase the activity of nerve tissue non-specifically, also can produce tetanic cramps. Often, such cramps are accompanied by evidence of hyperactivity of other nerve functions in addition to muscle stimulation. For instance, low blood calcium causes not only spasm of the muscles of the hands and wrists, but also a sensation of numbness and tingling around the mouth and other areas. Contractures : Contractures result when the muscles are unable to relax. The constant spasms are caused by a depletion of adenosine triphosphate (ATP), an energy chemical within the cell. This prevents muscle fiber relaxation. The nerves are inactive in this form of muscle spasm. Contractures can be inherited (e.g., McArdle's disease -- a defect of the breakdown of glycogen to sugar within the muscle cell) or acquired (e.g. hyperthyroid myopathy -- a muscle disease that is associated with an overactive thyroid). Cramps of this category are uncommon. Dystonic Cramps 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.