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 (overbreathing) , 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.
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.
Sometimes, tetanic cramps are indistinguishable
from "true" cramps. The accompanying changes of sensation or other
nerve functions may not be apparent.
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.
Do all muscle cramps fit
into the above categories?
No. Not all cramps are readily categorized in the preceding manner since these
categories best apply to cramps that are the major muscle problem a patient
has. Many cramps are a relatively minor part of nerve and muscle diseases;
other muscle symptoms are usually more prominent in these diseases. Examples
include amyotrophic lateral sclerosis (Lou Gehrig's disease) with weakness and
muscle wasting; radiculopathy (spinal nerve irritation or compression from
various causes) with pain, distortion or loss of sensation, and/or weakness;
diseases of the peripheral nerves, such as diabetic neuropathy, with distorted
and diminished sensation and weakness; and a number of primarily dystonic
muscle diseases.
Can medications cause
muscle 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.
Medications such as donepezil (Aricept-- used
for Alzheimer's disease) and neostigmine (Prostigmine and others -- used for myasthenia
gravis) as well as raloxifene (Evista- used to prevent osteoporosis in
postmenopausal women) have caused cramps. Tolcapone (Tasmar-- used for
Parkinson's disease) reportedly causes muscle cramps in at least 10% of
patients. "True" cramps are reported with nifedipine (Procardia and
others -- used for angina and high blood pressure, and other conditions) and
the asthma drugs terbutaline (Brethine)and albuterol
(Proventil, Ventolin, and others). Some medicines used to lower cholesterol, including
clofibrate (Atromid-S) and lovastatin (Mevacor), can
also lead to cramps.
Cramps are sometimes noted in addicted
individuals during withdrawal from medications and substances that have
sedative effects, including alcohol, barbiturates and other sedatives,
anti-anxiety agents such as benzodiazepines (e.g. Valium and Xanax), narcotics,
and other drugs.
Can vitamin deficiencies
cause muscle 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). The role of deficiency of these vitamins in causing cramps is
unknown.
Can poor circulation
cause muscle cramps?
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.
What are the symptoms of
common muscle cramps and how are they diagnosed?
Characteristically, a cramp is painful, often severely so. Usually, the
sufferer must stop whatever activity is underway 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. 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 of
skeletal muscle cramps?
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‡
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. (Learn this maneuver at a time when you don't
have the cramp!) Another technique involves pulling the toes up towards the
head while still lying in bed with the leg as straight as possible. For cramps
such as those that occur in writer's cramp, pressing the hand on a flat surface
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.
Interestingly, since the normal response of the muscle to cold is to shorten,
ice packs may also relax a cramp. 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 are not
generally needed to treat an ordinary cramp that is already present, since most
cramps subside spontaneously before enough medicine would be absorbed to even
have an effect.
One enthusiastic non-scientific recommendation
has been to firmly pinch the tissues above the lip, just under the nose, and
hold the pinch until the cramp stops (said to be within 15 minutes.) Of course,
why this might work, or even if it is causing anything that wouldn't have
happened anyway, is uncertain and no scientific study of this technique has
been reported.
In recent years, injections of therapeutic doses
of botulism toxin have been used successfully for some dystonic muscle
disorders that are localized to a limited group of muscles. A good response may
last several months or more, and the injection may then be repeated.
The treatment of cramps that are associated with
specific medical conditions generally focuses on treating the underlying
condition. Sometimes, additional medications specifically for cramps are
prescribed with certain of these conditions.
Of course, if cramps are severe, frequent,
persistent, respond poorly to simple treatments, or are not associated with an
obvious cause, 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 alluded to above, the possibilities are extremely varied
and include problems with circulation, nerves, metabolism, hormones,
medications, and nutrition. It is not common that muscle cramps would result
from a medical condition without some other obvious signs that the medical
condition is present.
In the long run, however, the most important
aspect of dealing with common muscle cramp disorders is prevention.
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. The vigorous use of diuretics
usually increases magnesium loss, and high levels of calcium intake (and
therefore of calcium excretion) tend to increase magnesium excretion. Magnesium
is present in many foods (greens, grains, meat and fish, bananas, apricots,
nuts, and soybeans) and some laxatives and antacids, but a supplemental dose of
50 to 100 milligrams of magnesium daily may be appropriate. Splitting the dose
and taking a portion several times during the day minimizes the tendency to diarrhea
that magnesium can cause.
Vitamin E has also been said to help minimize
cramp occurrence. Scientific studies documenting this effect are lacking, but
anecdotal reports are common and sometimes quite enthusiastic. Since vitamin E
is thought to have other beneficial health effects and is not toxic in usual
doses, taking 400 units of vitamin E daily is approved, recognizing that
documentation on its effect on cramps is lacking.
Are there particular
concerns for older adults?
Older adults should have periodic magnesium blood levels taken if they use
supplemental magnesium. Even a mild and otherwise not apparent degree of kidney
dysfunction, which is often seen in this age group, may lead to toxic levels of
magnesium with modest doses.
Recent studies have indicated that vitamin D (a vitamin
required for the normal absorption of calcium from food) deficiency is common
in some elderly individuals. Consequently, vitamin D replacement is important
for these people, taking appropriate care to avoid excessive vitamin D levels,
as these are toxic. An intake of 800 units of vitamin D daily is likely to be
fully adequate; at least 400 units daily is generally recommended.
While the more potent diuretics are associated
with an increased loss of calcium and magnesium, hydrochlorothiazide
(Hydrodiuril) and related diuretics are associated with calcium and magnesium
retention. Diuretics are commonly used for the treatment of hypertension and heart
failure. If cramps (or osteoporosis) are also a problem, the patient and doctor
may consider using hydrochlorothiazide or another thiazide type of diuretic if
otherwise feasible and appropriate.
Diuretics also cause sodium depletion and most
also cause potassium depletion. Many patients who use diuretics are also on
sodium restricted diets. Careful attention to the effects of diuretics on
sodium and potassium, and replacement of these elements as needed, is always
appropriate, even more so if cramps are also a problem.
Older adults often do not hydrate themselves
adequately, partly because the sense of thirst diminishes with age. This
situation is exaggerated in those who are treated with diuretics. For some,
simply increasing fluid intake to the generally recommended six to eight
glasses a day will improve the cramps. However, drinks with caffeine should not
be counted since they act on the kidneys to increase fluid loss. Individuals
who are on restricted fluid intake should consult their doctor on this issue
and must not ignore their recommended fluid intake limits.
For older people, it is uncommon to determine an
exact cause for night cramps. The best prevention involves implementing the following
measures: stretching regularly, adequate fluid intake, appropriate calcium and
vitamin D intake, supplemental vitamin E, and possibly -- with physician
consultation -- supplemental magnesium intake.
Are there medications to
prevent muscle cramps?
In recent times, the only medication that has been widely used to prevent, and
sometimes also to treat, cramps is quinine. Quinine acts by decreasing the
excitability of the muscles. It has also been shown to be effective in many,
but not all, scientific studies. However, quinine also causes birth defects and
miscarriages. It has also occasionally caused hypersensitivity reactions and a
deficiency of platelets, which are the blood components responsible for
clotting. Either of these reactions can be fatal. Quinine is also associated
with a cluster of symptoms called cinchonism (nausea, vomiting, headaches, and
deafness). Additionally, vision and heart irregularities can occur.
Consequently, quinine is now available in the
What is the prognosis of
recurrent muscle cramps?
Although cramps can be a great nuisance, they are a benign condition. Their
importance is limited to the discomfort and inconvenience they cause, or to the
diseases associated with them. Careful attention to the preceding recommendations
will greatly diminish the problem of cramps for most individuals. Those with
persistent or severe muscle cramps should seek medical attention.
Reference:
1. McGee SR. Muscle Cramps. Arch Intern Med,
1990;159:511-518.