By John C. Wolf, D.O.Associate Professor of Family Medicine Ohio University College of Osteopathic Medicine



Question: I've been having trouble with leg cramps waking me at night. I get up and stretch the muscle until it quits cramping. Sometimes the cramp is so hard that my muscles are sore the next day. What could be causing this?

Answer: Everyone can occasionally have leg cramps at night. While they are not unknown in children, they are most common in the elderly. Regardless of age, an episode of cramping is usually annoying because, as you describe, it interrupts sleep as well as causes discomfort. To explain this common disorder I need to remind you of the way muscles normally work.

We usually take the intricate operation of muscles for granted. A muscle contraction is caused by a complex interaction of several body systems -- including the brain, spinal cord, peripheral nerves, the junction of the individual nerve with the muscle fiber and the muscle itself. All of these parts, of course, also require a healthy supply of nourishing blood to work properly.

In a normal contraction only some of the individual muscle fibers are called upon to contract. Simultaneously with the contraction of muscles on one side of the joint, the muscles on the opposite side are signaled to relax. This produces the expected smooth coordinated movement. A more forceful effort, such as lifting a heavy weight, is accomplished by recruiting a greater number of muscle fibers to contract.

In a muscle cramp the number of muscle fibers that contract is large, as if you were picking up a heavy load, and the opposing muscles often don't relax. This abnormal and forceful contraction causes the typical muscle cramp pain. If it's sufficiently strong, the cramp can cause injury that makes the muscle sore for several days.

Research done to date hasn't identified precisely which step in the complex interaction of body systems produces nighttime muscle cramps. Most, however, suggest that the problem is with the nerves controlling the muscles rather than being a problem with the muscles themselves.

Some research points to a problem with the transition from wakefulness to sleep. When we dream about running, our legs don't move, but they certainly do when we are awake and running. Many individuals who have nocturnal leg cramps have them at the time of dreaming. That's why some researchers think that these cramps result from a subtle malfunction in the control system that normally "disconnects" our brain from the body movements we make in our dreams.

Most scientists who have investigated this question, however, believe that the problem is not a disorder within the brain. These researchers cite evidence that the problem is in the nerves after they leave the spinal cord but before they reach the muscles. For instance, the data show that people with conditions such as diabetes that affect the nerves outside the brain and spinal cord (doctors call them peripheral nerves) have an increased frequency of leg cramps. Similarly, those with circulation problems that prevent these peripheral nerves from getting proper nourishment are more likely to have nocturnal cramps.

The best way to stop a leg cramp is to stretch the sore muscle just as you have done. When this happens to me, I jump out of bed and do a less than graceful pirouette until the cramp subsides.

Several medicines have been used for nocturnal leg cramps. Quinine has been around the longest, but its benefit is modest and the drug is not free of side effects. Calcium channel blockers are also occasionally of benefit. Talk to your doctor. He or she will search for a "cause" of your leg cramps by checking your nervous system and evaluating your circulation. Unfortunately, in most cases neither a simple cause nor an effective remedy is to be found.


"Family Medicine" is a weekly column.

To submit questions, write to: John C. Wolf, D.O., Ohio University College of Osteopathic Medicine, Grosvenor Hall, Athens, Ohio 45701.

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