Nocturnal leg cramps are sudden, involuntary contractions of the calf muscles that occur during the night or while at rest. The cramps can affect persons in any age-group, but they tend to occur in middle-aged and older populations. Sometimes muscles in the soles of the feet also cramp. Research has not identified precisely what causes nighttime muscle cramps. The problem is most likely with the nerves controlling the muscles rather than with the muscles themselves. Some research points to a problem with the transition from wakefulness to sleep. 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 separates our brain from the body movements we make in our dreams. However, most scientists believe that the problem is not a disorder within the brain.

Sometimes the cramps are caused by overexertion of the muscles, structural disorders (flat feet), standing on concrete, prolonged sitting, inappropriate leg positions while sedentary, or dehydration. Doctors do know that those who are more muscular seem to have more leg cramps. Less common causes include diabetes, Parkinson's disease, hypoglycemia, anemia, thyroid and endocrine disorders and use of some medications.

Low levels of certain minerals known as electrolytes—magnesium, potassium, calcium and sodium—have long been linked to leg cramps. (Marathon runners sweating out the miles are particularly prone to this variety.) Certain drugs, such as diuretics have also been cited as a cause of leg cramps. Dialysis patients often complain of leg cramps, and pregnancy is also a factor.

To prevent cramping consider the regular use of supplements, especially calcium, magnesium, potassium and sodium (only if your sodium intake is low or if you sweat a lot). Stretching your calves regularly during the day and at night will help. You can often prevent night cramps by exhausting the stretch reflex before you go to bed by stretching your calf muscles with wall pushups and applying a heating pad for 10 minutes before going to bed. Keeping blankets loose at the foot of the bed will help prevent unnatural positioning of your feet and toes which can cause night time cramping.

When cramping occurs, try walking on the affected leg and then elevate it. Stretch your calf by grabbing your toes and pulling them upward toward your knee, especially with you leg extended straight. Take a hot shower or warm bath, or apply an ice massage to the cramped muscle.

Persistent or severe leg cramps often are treated with medication. Such medications include diphenhydramine hydrochloride (Benadryl), prescription muscle relaxants (off-label use) such as meprobamate (Equanil, Miltown) and verapamil hydrochloride (Calan, Isoptin, Verelan). Quinine, while effective, has too many side effects and has been banned in the US for this use.