Cramps part 1

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Muscle Cramps

(Of Skeletal Muscles)

POWER POINTS

* A muscle cramp is an involuntarily and forcibly contracted muscle that

does not relax.

* Almost everyone experiences a cramp at some time in their life.

* There are a variety of types and causes of muscle cramps.

* Numerous medicines can cause cramps.

* Most muscle cramps can be stopped if the muscle can be stretched.

* Muscle cramps can often be prevented.

What are 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 (one estimate is about 95%)

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.

What are the types and causes of muscle 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. " 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 exaggerated

physical activities.

Rest Cramps. Especially in older adults, cramps at rest (often during the

night) are very common. Rest cramps may be experienced at any age, however,

including during childhood. While not life-threatening, night cramps can be

very disruptive of sleep and otherwise quite disturbing. They sometimes recur

frequently (that is, many times a night, and/or many nights each week) and

are very painful. The actual cause of night cramps is unknown. Sometimes,

such cramps seem to be initiated by making a movement that shortens the

muscle, which then cramps. An example is pointing the toe down while lying in

bed, which shortens the calf muscle, a common site of 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 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 in seniors. 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, with fluid in the abdominal cavity (ascites). Similarly, cramps

are a relatively frequent complication of the rapid body fluid changes that

occur during artificial kidney treatment (hemodialysis).

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 levels of calcium and

magnesium are common in a normal pregnancy unless these minerals are

supplemented to the diet. Cramps are seen in any circumstance that decreases

the availability of calcium or magnesium in body fluids, such as from

diuretics, hyperventilation (over breathing) , excessive vomiting, inadequate

calcium and/or magnesium in the diet, inadequate calcium absorption due to

vitamin D deficiency, poor function of the parathyroid gland (a tiny gland in

the neck that regulates calcium balance) and other conditions.

Low Potassium. Low potassium levels occasionally cause muscle cramps. More

often, low potassium is associated with muscle weakness.