Last reviewed February 27, 2013
The situation is remarkably common. You're sound asleep and suddenly you awaken with a stabbing, searing pain in the calf. Relief comes only by jumping out of bed and standing up. For many, this scenario repeats night after night, sometimes more than once. If you're lucky enough never to have leg cramps at night (also called nocturnal leg cramps), perhaps you've had "writer's cramp" or exercise-related muscle cramps. Each of these is marked by sudden, intense muscle pain or contractions, even though muscle function is normal and there's no pain between episodes.
All are called "muscle cramps," but they occur in different situations and may have different mechanisms. More important, treatment can differ — that is, when there is any treatment at all.
A common misconception is that muscle cramps are caused by abnormal potassium, sodium or calcium. In fact, for most types of cramps all of these are normal and treatment to replenish these minerals, known as electrolytes, has no clear effect.
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Nocturnal Leg Cramps
The cause of nighttime cramps in the legs is unknown. They seem to increase in frequency with age but are not clearly associated with circulation problems or arthritis. The evaluation of people with this problem usually includes measurement of blood sugar, electrolytes and minerals (such as potassium, sodium, magnesium and calcium). Still, of all the people with this condition — and there are a lot of them — a cause can be found only rarely.
Some research has associated nocturnal leg cramps with diabetes, flat feet, prolonged sitting, and dehydration with salt depletion (as may occur after exercise). Medications that alter electrolytes, such as diuretic medicines that promote salt and/or potassium loss, may play a role in some cases.
There is no single, clearly beneficial treatment, but some people swear by one or more of the following:
- Stretching and regular exercise
- Drinking more fluids before and after exercise
- Applying heat to the muscles that have been cramping before bed
- Wearing better footwear, such as shoes or inserts with arch support
Medications have no proven role, but many people report improvement with:
- Muscle relaxants (such as methocarbamol or cyclobenzaprine)
- Vitamin E
- Diphenhydramine (Benadryl)
Although nocturnal leg cramps are not dangerous, they are quite painful and they disrupt sleep, so it's worthwhile having an evaluation to see if a specific cause or trigger can be identified and to review acceptably safe treatment options.
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Also called graphospasm, writer's cramp is defined as "a cramp or spasm of the muscles of the fingers, hand, and forearm during writing." It is a form of focal dystonia, meaning that in one area of the body muscles involuntarily contract, causing abnormal postures or movements. Other examples of dystonia include genetic diseases (such as early-onset generalized dystonia), and it also can be a complication of Wilson's disease.
The problem that occurs in dystonias is that instead of the normal relaxation of one muscle group when its opposing muscles contract, both sets of muscles contract. For example, when the fingers are extended (straightened out) the finger flexors typically relax. When making a fist, the fingers flex and the extensor muscles should relax. But with dystonia, both sets contract and the result is what is commonly called a cramp, with the hand stuck in a painful position, unable to relax. The precise reasons are uncertain, but it is thought that insufficient nerve signals from the hand into the spinal cord and brain lead to inadequate "relaxation signal" from the brain to the hand.
People with writer's cramp may notice that the more they try to write, the worse the cramping gets; there may even be involuntary jerking of the hand. Up to one-third of affected people also suffer from a tremor, an involuntary, continuous movement of the hands. Repetitive motion, such as writing or typing, and family history seem to be risk factors for this condition, although more than 90% of people with writer's cramp have no other affected family members.
Just as with nocturnal leg cramps, most cases have no identifiable cause, but in rare cases writer's cramp is associated with disc disease in the neck, certain drugs (such as lithium), and brain disease (including stroke, abnormal blood vessel formations and tumors).
Treatment is not routinely effective, but recommendations include:
- Change of activity — Dictate long documents rather than type or write them. Sometimes, using a pen or pencil with a larger grip improves the situation.
- Try to gain control — Relaxation techniques, hypnosis and biofeedback all have been reported to be helpful in some cases.
- Medication treatment (with your doctor's supervision) — Medications include trihexyphenidyl (Artane), propranolol (Inderal and others) or botulinum toxin (Botox) injections.
For most people with writer's cramp, there is a safe and effective solution, whether requiring a medication or not.
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Exercise-Related Muscle Cramps
Nothing puts a damper on exercise faster than a muscle cramp early in the going. Cramps in a calf are among the most common problems associated with exercise, especially in heat or humidity. But even though it's common, the cause remains uncertain.
Some experts believe muscle fatigue is the problem and point out that muscle cramping during exercise is most common among untrained athletes or early in an athletic season, before peak physical conditioning has been reached. Others suggest that dehydration and electrolyte imbalance are the most important triggers, although blood tests for common electrolytes (such as sodium and potassium) are typically normal.
In fact, in most cases, there is rarely any clear explanation for the problem. While it's long been assumed that dehydration and electrolyte imbalance are important contributors to muscle cramping after exercise, recent studies have challenged these explanations. For example, a small study published in 2010 found that:
- Dehydration alone did not make exercising muscles more likely to cramp.
- Pickle juice (or vinegar) rapidly relieved muscle cramps after exercise. (Yes, pickle juice!)
- The effect of pickle juice was so fast that it was unlikely it was replacing electrolytes or fluids.
These findings led the researchers to suggest that exercise-associated muscle cramping may be due to misfiring nerves in tired muscles and that something in pickle juice — the vinegar, perhaps — might send nerve signals to cramping muscles telling them to relax.
So, what's a well-intentioned exerciser to do? Warm up for five to 10 minutes in the first part of your exercise routine and gently stretch during and after exercise. Drink plenty of fluids, and start your exercise program slowly, building up endurance and strength gradually. It may be hard to predict when you'll get a cramp exercising, but they predictably do go away and rarely cause any long-term impediment to exercise. When you get one, stop exercising and stretch the muscle out until the cramp goes away and does not feel like it's about to return — it may take several minutes or more. You may want to try pickle juice; in the study described above, just 2.5 ounces did the trick.
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Diseases Associated With Muscle Cramps
While the vast majority of people with muscle cramps are perfectly healthy, cramps are occasionally a sign of illness. Besides those conditions mentioned above (see nocturnal leg cramps), diseases and conditions associated with muscle cramps include:
- Metabolic disorders of the muscles — For example, several types of muscular dystrophy, including myotonic dystrophy, may cause muscle cramps.
- Dialysis, a blood cleansing procedure for people with kidney failure, is often accompanied by muscle cramps.
- Parkinson's disease
- Chronic venous insufficiency — Though the reason is uncertain, leg cramps are common in people with poor circulation in the veins of the legs.
- Pregnancy, perhaps because of low blood magnesium levels
- Abnormalities in the regulation of blood sugar, including diabetes and hypoglycemia, are said to be associated with muscle cramps.
- Medications, including certain asthma medicines (inhaled bronchodilators), blood pressure or heart medicines, and chemotherapy agents
If you have severe or long-lasting leg cramps or if you have one of the associated diseases mentioned above, talk with your doctor about treatment options.
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Why Do Cramps Matter?
While common cramping problems are rarely dangerous — and that probably includes the dreaded cramps associated with swimming — they can be a terribly bothersome problem for perfectly healthy people.
They do matter. Pain can reduce your quality of life and some muscle cramps will disrupt sleep, causing daytime fatigue and difficulty concentrating. People with muscle cramps may seek medical attention and, if they take medications for the problem, experience side effects. All of this comes at a price. And for the rare person with a medical condition associated with cramping (such as muscular dystrophy or thyroid disease), detection of that condition may be quite important.
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If you get muscle cramps, don't assume it's because of abnormalities in electrolytes — that may be one of the commonest myths around. You can eat a banana or drink orange juice, hoping the extra potassium will prevent recurrent cramps, and that may work. But it's just as likely that you will occasionally have more cramps.
While there are steps you can take, the precise reason you're having cramps and another person is not is probably unknowable. Fortunately, the outlook is good — annoying, yes, but dangerous, almost never.
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Robert H. Shmerling, M.D., is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.