Up to 60 percent of North American adults suffer from night-time leg cramps, a sudden painful contraction usually of the calf muscles that can last from a few seconds up to 10 minutes or more. Doctors do not know what causes most cases of leg cramps, but usually they are not caused by dehydration or lack of minerals. The leading theory is that most leg cramps come from the lack of a normal nerve reflex that causes a muscle fiber to relax when it is held in contraction. That is why people who suffer recurrent leg cramps should be checked for conditions that can cause nerve damage such as vitamin B12 defciency or diabetes. Cramps occur most often at night when you are sleeping, when you exercise vigorously, when you tear a muscle, or when you keep your leg in an awkward position, such as sitting in a chair in the same position for a long time. If you have frequent night-time leg cramps, check with your doctor.
What is a Muscle Cramp?
When you turn during sleep, you contract your calf muscles, which stretches their tendons. This stimulates nerve stretch receptors in the tendon and sends a message back to the spinal cord, telling the calf muscles to contract. After you contract a muscle, reflex messages are sent along nerves to the spinal cord to relax that muscle. If the message to relax is blocked, the muscle stays contracted and you develop a cramp. Cramping during sleep is usually due to an exaggeration of the normal muscle reflex that causes the muscle to stay contracted and hurt.
Older people and those who do not exercise are at increased risk for cramps because they have smaller and weaker muscles. Cramps are more likely to occur in hot weather because muscles fatigue earlier with higher temperatures. Cramps are more likely to occur during intense exercise that requires you to use your fast twitch strength fibers that fatigue earlier than your slow twitch endurance fibers.
What To Do When You Develop a Leg Cramp
When you get a leg cramp, you should gently try to walk it out while you massage the contracted muscle with your hands. Don’t put great force on the contracted muscle because you may tear it. If the cramp continues, apply cold compresses, which can relax the contracted muscle and numb the pain. Keep on gently massaging the muscle.
Preventing Leg Cramps
You can often prevent night-time leg cramps if you:
• exhaust the stretch reflex before you go to bed by stretching your calf muscles
• apply a heating pad for 10 minutes before you go to sleep
• start a regular exercise program to strengthen your calf muscles. If you are a non-exerciser, the best exercise may be a stationary bicycle or a spinning class.
Quinine may be used to treat night-time leg cramps (Brit Med J, Jan 7, 1995; 310(6971):13-17), but the U.S. Food and Drug Administration stopped over-the-counter marketing of this remedy because of concerns about irregular heartbeats. Doctors can still prescribe quinine pills for relief of leg cramps, but they can cause birth defects and miscarriages, so they should not be taken by a pregnant woman. Quinine can also cause ringing in the ears, headache, nausea, disturbed vision, chest pain, asthma and other problems.
Work-Up for Frequent Leg Cramps
Most causes of leg cramps are harmless, but if you suffer frequent leg cramps, you need a detailed medical workup; check with your doctor. Treatable causes of frequent leg cramps include:
• all conditions that can cause blood vessel damage such as arteriosclerosis
• partially obstructed blood vessels
• pinched nerves in the back
• muscle damage
• nerve damage
• kidney disease
• abnormal mineral levels such as lack of potassium or calcium
• vitamin B12 deficiency
• abnormal hormone levels such as low thyroid
• medications such as birth control pills, diuretics (which are often prescribed for people with high blood pressure), steroids, raloxifene and teriparatide, asthma medication such as albuterol, pain meds such as naproxen or pregabalin, statin drugs to lower cholesterol, and so forth (BMJ Clin Evid, 2015; 2015: 1113; Am Fam Physician, 2012, Aug 15;86(4):350-3).
• up to 30% of night time leg cramps can be due to venous insufficiency or varicose veins. Vein specialists can do ultrasound evaluation of valves to see if they gap, allowing stretching of the vein to create contracture (cramp). This can be easily treated using laser or chemicals to close the inefficient valves or veins.
When you get a leg cramp at night, get up and start walking cautiously while gently massaging the cramped muscle. The cramp should ease up within a few seconds. Stop walking immediately if the pain worsens because you can tear the muscle. For the next few nights, try stretching your calf muscles to exhaust the stretch reflex with “wall push-ups” before you go to bed. Stand about an arm’s length from a wall or countertop with both feet flat on the ground. Place your hands on the wall and slowly bend your elbows to bring your upper body closer to the wall. Hold for the count of ten and then push your self away from the wall by straightening your elbows. Repeat several times.
Note: Gene Mirkin, DPM contributed to this report.