by Gabe Mirkin, M.D.
Muscle cramps occur most often at night when you are sleeping, but they also can occur when you exercise vigorously, tear a muscle, or keep one leg in an awkward position, such as sitting in a chair in the same position for a long time. Muscle cramps are classified into those that occur during exercise and those that can occur at any time not related to exercise, usually at night.
Cramps That Occur During Exercise
Lack of electrolytes is a more common cause of muscle cramps during exercise than lack of water (BMJ Open Sport Exerc Med, Mar 5, 2019;5(1):e000478). Electrolytes are minerals that are essential for body functions, including sodium, potassium, calcium, bicarbonate, magnesium, chloride, and phosphate. Having low blood levels of sodium (salt) is a well-known cause of muscle cramps (Clin J Am Soc Nephrol. 2007;2:151–161). Dehydration, by itself, is a far less common cause of cramps (Br J Sports Med, 2013 Jul;47(11):710-4). You can be salt deficient and still have normal blood levels of electrolytes.
Researchers in Australia studied runners who drank either plain water or an electrolyte solution before and after exercise. They found that the runners were at increased risk for suffering muscle cramps when they drank plain water, probably because water dilutes the electrolyte concentration in the body and doesn’t replace what they lost through sweating (J Int Soc Sports Nutr, Mar 15, 2021;18(1):22). In this study, 10 men ran multiple sessions on a downhill treadmill in a hot (95 degree F) room for 40 to 60 minutes, to sweat enough to lose 1.5-2 percent of their body weight (about two pounds). They were then tested before, immediately after and 40 minutes after exercising, with two trials: first, drinking plain water; and second, drinking an electrolyte solution.
The tests used a special device that electrically stimulated their calf muscles enough to cause muscle cramps. The runners developed muscle cramps on much lower electrical stimulation frequencies after drinking plain water than after drinking the electrolyte solution. These results suggest that lack of electrolytes is more likely to cause muscle cramps than just lack of water (dehydration).
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.
Night-Time Leg Cramps
Up to 60 percent of North American adults suffer from occasional night-time leg cramps, a sudden painful contraction usually of the calf muscles that can last from a few seconds up to 10 or more minutes. Doctors do not know what causes these cramps, but most of the time, they are not caused by dehydration or lack of minerals. The leading theory is that most night-time leg cramps are caused by lack of a normal nerve reflex that causes a muscle fiber to relax when it is held in contraction (J Sports Sci, 1997 Jun;15(3):277-85). That is why people who suffer recurrent leg cramps should be checked for:
• all conditions that can cause nerve damage, including lack of vitamin B12 and diabetes
• all conditions that can cause blood vessel damage such as arteriosclerosis
• partially obstructed blood vessels
• pinched nerves in the back
• muscle damage
• abnormal mineral levels
• abnormal hormone levels such as low thyroid
• kidney disease
• arthritis
• dehydration
• use of several medications such as statins, birth control pills, diuretics, steroids, asthma medication such as albuterol, raloxifene, naproxen, or teriparatide (BMJ Clin Evid, 2015:1113).
If you have recurrent night-time leg cramps, check with your doctor.
What Causes Leg Cramps?
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 that muscle 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 leg cramps because they have smaller and weaker muscles.
Preventing Night-Time Leg Cramps
If you do not have a serious cause, you can often prevent night cramps by:
• exhausting the stretch reflex before you go to bed by stretching your calf muscles (using wall pushups or a similar exercise)
• applying a heating pad for 10 minutes before you go to sleep
• starting a regular supervised exercise program to strengthen your calf muscles. If you are a non-exerciser, I recommend a stationary bicycle.
The only drug that has been shown to be effective in preventing night-time leg cramps is quinine (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 since they can cause birth defects and miscarriages, they should never be taken by a pregnant woman. Quinine can also cause ringing in the ears, headache, nausea, disturbed vision, chest pain, asthma and other problems. Some people may benefit from calcium channel blockers, such as amlodipine, or Carisoprodol (a muscle relaxer that blocks pain).
Treating a Leg Cramp
When you get a leg cramp, stop whatever you are doing and try to gently walk it out while you massage the contracted muscle with your hands. Never put force on the contracted muscle because you may tear it. If the cramp continues, apply cool compresses, which can relax the contracted muscle and numb pain. Keep on gently massaging the muscle.
My Recommendations
Most leg cramps are harmless, but frequent muscle cramps can be a sign of serious medical conditions. If you suffer leg cramps only during exercise, eat salty foods or drink electrolyte solutions, not plain water, before and after you exercise. If that doesn’t stop the cramps, you need a complete medical work up. People who suffer frequent night-time leg cramps that do not respond to the simple steps listed above also need a detailed medical work up. Check with your doctor.
Gabe Mirkin, M.D., is a sports medicine doctor and fitness guru. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin has run more than 40 marathons and is now a serious tandem bike rider with his wife, Diana. His website is http://drmirkin.com/. Click to read Gabe’s full bio.
Consult your healthcare provider! Once I reached my mid-60s, I would get painful cramps affecting opposing muscles (ie, hamstring and quads at the same time) hours after a hard ride. This is despite re-hydrating and taking electrolytes. Sometimes I would even pass out during the cramp episodes, resulting in assorted fall-related injuries. It turns out I was generally low in magnesium and told to take Mg supplements daily. That has stopped most cramping episodes. When I feel the warning spasms, taking another Mg tablet stops them.
Again, check with your health care provider! Each of us likely has a different set of mineral deficiencies.
The passing out, the doc suggested, is that the extreme muscle spasms were sending my brain feed-back signals and causing a neuro overload.
I’ve always had cramping issues, and I’ve always sweated more than most people. During heavy exertion, especially on hot days, salt capsules help tremendously.
My once-common night cramp ‘charlie-horses’ are gone since I gave up eating ice cream.
HTH.
I had nighttime leg cramps for many years after hard rides. And a touch of restless leg syndrome after such rides. Magnesium supplement before bed has totally cleared the problem for me. Plus it seems to help me fall asleep.
Rarely get cramps anymore after moving to CO from Phoenix 10 years ago, but taking a few antacids have always resolved the cramps in just a few minutes, either on the bike or at night.
I have poor circulation in my legs. I have had three knee surgeries. I most often suffer from cramps in the evening after sitting still for a long while, and then starting to move. Often after reading in bed, then turning off the light.
After trying bananas, pickles, antacids, endless handfuls of potassium, magnesium, and calcium pills, I find that apple cider vinegar works wonders.
I add a shot of vinegar and a half teaspoon of salt to my water bottles.
At night, if I have to get up due to a cramp, I put a half inch of apple cider vinegar in a water glass and fill it up with water. After I chug this down, the cramps are gone in a few minutes.
I am not sure why this works. I have read various explanations about the vinegar increasing alkalinity in the body, despite the fact that it is acidic. That makes little sense. But after trying different things for decades, the vinegar works for me.
By the way, we have an article with all the top reader solutions for cramping here:
https://www.roadbikerider.com/solutions-for-cramps-d1/
And People’s Pharmacy has some good articles on the subject with their reader suggestions like this one:
https://www.peoplespharmacy.com/articles/leg-cramp-remedies-are-as-close-as-the-fridge
I am astounded that the the loss of electrolytes is still being put forward as a cause in cramping. Was this article written about 20 years ago? Modern research is very inconclusive but what is now being put forward for causing muscle cramps is local muscle fatigue- but again the real and main cause(s) is not known… but the loss of electrolytes may be a contributing factor – not the main cause.