What are leg cramps?
If you’ve ever felt the muscles in your legs suddenly tighten, and become painful and stiff, you’ve experienced leg cramps. They usually last seconds, but in some cases can last up to ten minutes, or perhaps even longer [1]. Some people may also get muscle spasms, or twitches. Scientists don’t agree on what causes leg cramps, why they vary in duration, or why some people get them, and others not at all. Does dehydration cause leg cramps? Here’s a rundown of what we know about leg cramps and hydration.
What causes leg cramps?
More than 100 years ago, scientists noticed that the occurrence of leg cramps were related to the amount of salt in your body, or perhaps lack thereof [2]. You lose salt all the time, through everyday activities, but it often takes more extreme conditions—like exercise or the stomach flu—to throw your body’s salt levels off-balance. Scientists have theorized that having the wrong amount of salt in your body fluids may lead to cramps. Or rather, becoming dehydrated, which changes the amount of salt in your fluids, may lead to cramps.
Scientists have also observed that leg cramps occur more frequently in older age, in pregnancy, in liver disease, and if you take certain types of medications [1]. Leg cramps are also often experienced during or straight after exercise; these are called Exercise-Associated-Muscle-Cramps, or EAMCs [3]. In exercise you lose lots of salt and water, mostly through sweat, and you become dehydrated. This may explain why leg cramps occur more often in exercise. But it’s hard to say definitively that dehydration causes cramps.
The question, therefore, is how could these changes in salt and water levels in your body cause leg cramps?
What happens in a cramp?
A muscle cramp, twitch, or spasm, happens when the muscles in part of your body contract very suddenly, and remain contracted, sometimes for a long period of time.
When you want to contract a muscle, your nerves send a signal to the muscle telling it to get shorter. Your nerves open and close tiny holes that allow salt to move in and out of your cells (we can call them salt-gates) in order to make the signal, and transmit it to your muscles. Your muscles do the same thing, opening and closing salt-gates, in order to contract, and relax again.
If you are dehydrated, the amount of water and salt in your body changes, which might cause these salt-gates to function less frequently, or change the total amount of salt moving in and out of your cells. This could mess with the signals from your nerves to your muscles, and also within your muscles themselves, leading to twitching and cramp.
So, are cramps due to dehydration?
It’s hard to say whether dehydration causes leg cramps. As we’ve discussed, many people experience leg cramps for lots of reasons, not only during exercise—when you’re likely to lose water and salt—but also in lots of other situations that don’t make you dehydrated. Scientists have lots of theories about cramps and how they happen. Although one called the ‘electrolyte depletion hypothesis,’ is based on dehydration, we can’t rule out the others [3].
So, there may well be a link between leg cramps, twitching and spasms, and dehydration. Although it hasn’t been proven, it’s still a good idea to keep hydrated during and after exercise, and if you are experiencing leg cramps. Even if dehydration isn’t the cause, restoring the right balance of salt and water in your body will help you feel more energized, awake and ready to go. So it’s always a good idea to hydrate.
Are you concerned about your own hydration levels? Take the quiz below to find the best Hydrant for your hydration routine.
Writer: Ailsa McKinlay
Editor: Elizabeth Trelstad, hellobeaker.com
References
[1] https://www.nhs.uk/conditions/leg-cramps/ The NHS is the UK’s National Health Service, offering professional advice, care and support, both in person, and through their comprehensive online services, such as this piece on the basics of leg cramps.
[2] Ind Med Gaz. 1909 Nov;44(11):401-408. The Indications and Technique of Transfusion in Cholera, with a Note on Cholera in Europeans in Calcutta. Rogers. L. (In this piece, L. Rogers describes the muscle cramps he saw in people with Cholera, a disease that makes you dehydrated)
[3] Giuriato, G. Muscle cramps: A comparison of the two-leading hypothesis Journal of Electromyography and Kinesiology, Volume 41, August 2018, Pages 89-95 (This report is written by some scientists looking at the most recent evidence about leg cramps).
