Think back to the last time you had a muscle cramp during or after a workout.
If it was a severe muscle cramp, you probably remember being in extreme pain for several minutes. If it was a moderate or light muscle cramp, it was probably not too painful, but annoying nonetheless.
In this podcast you’ll learn:
1. The scientific definition of exercise related muscle cramps.
2. The most common theory as to what causes exercise related muscle cramps.
3. Why this theory is flawed (and how it’s been used to sell a lot of sports drinks).
4. What the latest evidence has to say on what really causes muscle cramps.
5. How you can prevent and treat muscle cramps.
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**Armi Legge:** Think back to the last time you had a muscle cramp during a workout. If it was a severe muscle cramp, you probably remember being in extreme pain for several minutes. If it was a moderate or light muscle cramp, it probably wasn’t too painful but annoying nonetheless. Muscle cramps aren’t generally dangerous but they are a pain in the butt, or, more commonly, a pain the leg, foot, and calf. It’s not like you’re having a rusty butter knife shoved in your leg but they are painful enough to ruin your workout.
Muscle cramps are also extremely common in athletes. Studies have shown that as many as 67% of triathletes, 18% – 70% of marathon runners and cyclists, and 30% – 53% of American football players cramp during or shortly after training and competition. In this podcast, you’re going to learn almost everything there is to know about exercise related muscle cramps.
Even if you don’t cramp often or never cramp, there are three reasons you are still going to love this episode:
1. You probably know someone who often gets muscle cramps during or after exercise. If not, you probably will meet someone who does eventually. If this person has serious muscle cramps on a regular basis, you can bet they will be grateful for advice that actually works. When you are the one person who is able to help your exercise buddies stop cramping or avoid cramps altogether, you are going to look totally awesome.
2. There are a ton of products that are now being sold to help stop muscle cramps. You or your friends may have spent some of your money on them or may be tempted to in the future. Don’t. Most of these products don’t work and you’re going to learn why in this podcast. Even if you haven’t bought these products specifically to stop muscle cramps, you will be able to help your friends save their money and you’ll be a more informed consumer, which is always a good thing.
3. Since you’re listening to this podcast, you’re probably kind of an exercise nerd like me. If that’s the case, you’re going to love this podcast because exercise related muscle cramps are a fascinating, poorly understand topic that is surrounded by several juicy myths that we’ll cover in a moment. By learning about the real causes of muscle cramps, you’ll also get a better understanding about how the human body fatigues and responds to exercise.
As an added bonus, you will also hone your critical thinking skills along the way.
Before you learn about muscle cramps, remember you can find more information like this by subscribing to the Impruvism email newsletter. If you want to know the most research proven ways to become stronger, faster, healthier, better at interacting with others, and more productive, all while developing your own set of critical thinking skills, you should navigate to www.impruvism.com, enter your email address in the box on the right side of the page, and click the button below that says “subscribe.” After you do, you’ll get free updates from the blog, including articles, interviews, and some exclusive bonus content that is only available for people subscribed to the email newsletter.
Now it’s time for you to become an expert on muscle cramps.
In the last podcast episode, you learned about a study that found drinking pickle juice helped cramps go away faster than drinking water or nothing at all. In this podcast, you’re going to learn five things:
1. The scientific definition of exercise related muscle cramps.
2. The most theory as to what causes exercise related muscle cramps.
3. Why this theory is flawed and how it has been used to sell a lot of sports drinks.
4. What the latest evidence has to say on what really causes muscle cramps.
5. Finally, how you can use this new knowledge to prevent and treat your muscle cramps, or look like a champ by helping others stop their muscle cramps.
Let’s start by quickly defining exercise related muscle cramps. To quote from a review published in 2010, exercise related muscle cramps are “involuntary, generally painful contractions of a muscle or muscle group.” Another review called them “spasmodic, painful, involuntary contraction of the skeletal muscle that occurs during or immediately after exercise.” We’re mostly going to focus on cramps that occur around workouts, but exercise-related muscle cramps are also common among people who have jobs that force them to use a particular muscle group more than usual. Typists often get hand cramps, for instance.
Much of this information is also relevant to you if you get leg cramps at night, which are also common. We will not be talking about heat cramps or cramps caused by other conditions such as hormone, neurological, and vascular disorders. For the rest of this podcast, when I say “muscle cramp,” I mean an exercise-related muscle cramp. Now let’s talk about what causes muscle cramps.
The prevailing theory about what causes muscle cramps is called “the electrolyte depletion/dehydration hypothesis.” According to this theory, muscle cramps are caused either by dehydration, excessively high or low electrolyte levels, or both. Electrolytes are molecules that conduct electoral signals throughout your body and serve a few other functions that aren’t super relevant to muscle cramps. The five major electrolytes you lose in sweat are sodium, potassium, calcium, magnesium, and chloride. When you lose enough electrolytes and water through sweat, the nerve impulses from your brain become deranged and your muscles fire incorrectly, causing a muscle cramp.
This theory started back in the early 1900s. Researchers found that workers in shipyards and mines who cramped often had high chloride levels in their sweat. They decided that the workers must be sweating out their electrolytes, causing muscle cramps. Keep in mind that no one tested the sweat of the workers who didn’t cramp. You will see why that’s important in a moment.
During the construction of the Hoover Dam, researchers also noted that workers who cramped were often able to recover by drinking salty milk. This theory quickly became accepted as fact and a few early studies did find that marathon runners who cramped often had low electrolyte levels at the end of races. However, there are five major problems with the electrolyte dehydration theory of muscle cramps:
1. Until recently, there wasn’t a standardized way to cause muscle cramps, so there were no controlled trials to prove or disprove whether or not low electrolyte levels cause muscle cramps. As you learned in the last podcast, researchers now create muscle cramps by electrocuting volunteers, which isn’t necessarily a good replication of exercise related muscle cramps. Because of this lack of controlled data, we have to rely on observational evidence and our understanding of basic human physiology to prove or disprove what really causes muscle cramps. This leads us to number two.
2. Based on what we know about human sweat, the electrolyte depletion theory doesn’t make much sense. When you sweat, your blood actually becomes more concentrated with electrolytes, or what researchers call “hypertonic.” Your sweat is mostly water and you only lose a small amount of electrolytes. This is true even for so-called “salty sweaters.” There is no definition of what a “salty sweater” is, and even the “saltiest sweaters” still sweat out far more water than electrolytes.
3. If cramps were caused by loss of electrolytes, or dehydration, you would expect many, if not all, the muscles to cramp since all your muscles would be low on electrolytes. This is what happens when people become dangerously and clinically low on electrolytes. On the other hand, exercise related muscle cramps almost always occur in the muscles that are used most during the activity. For example, one study found that 95% of all muscle cramps that occurred during the Two Oceans Ultramarathon happened in the leg muscles, the quads, hamstrings, and calves of the runners, or the muscles they were using the most.
4. A few early studies found that athletes who cramped had low electrolyte levels; however, no one measured the electrolyte levels of the athletes who didn’t cramp. More studies have measured this. They have found fairly consistently that the people who don’t cramp generally have about the same levels of dehydration and electrolyte depletion as the athletes who do cramp.
A 1990 study found there was no relationship between potassium levels and cramps in cyclists riding after five hours, meaning those who cramped were no more or less likely to have high or low potassium levels.
Another 2004 study, which you just learned about, compared runners who cramped during the Two Oceans 56km Ultramarathon to those who did not cramp. That’s just over 30 miles for non-metric oriented people. They found that people who cramped had lower sodium levels but higher magnesium levels. In both cases, the differences were also very small.
If there runners’ cramps were caused by dehydration, then you would expect their sodium levels to be higher since, as you just learned, sweating causes the electrolyte concentration of the plasma to rise. There runners who did not cramp also lost more body weight after the race, which is a sign they were more dehydrated than those who did not cramp. If anything, this study indicates that cramping is associated with drinking too much.
A study the following year found almost the same results in Ironman triathletes. Those who cramped lost about as much body weight as those who did not cramp, which indicates that dehydration was not related to their cramps. Once again, there was no significant difference in electrolyte levels between those who did cramp and those who did not.
A more recent study, published in 2011 in the British Journal of Sports Medicine, again found that Ironman athletes who cramped had the same electrolyte levels as those who did not cramp. This study also found that the athletes who pushed themselves the hardest relative to their past performances and training had the highest risk of cramping.
Controlled studies have also generally found that consuming electrolytes doesn’t stop muscle cramps. In one study, researchers caused muscle cramps by putting subjects through a series of calf exercises in the heat. During the first test, the subjects consumed nothing after they cramped and the researchers measured how long their cramps lasted. On the second occasion, the subjects consumed Gatorade throughout the test. 9 out of 13 people cramped in the Gatorade group while only 7 out of 13 people cramped in the group that consumed nothing. It did take longer for those who took Gatorade to cramp, but here is the interesting thing. The same 7 subjects who cramped without Gatorade also cramped when they did drink Gatorade, which indicates that the electrolytes and carbs didn’t stop the cramps.
There was no control group in the study that consumed just water, so it is impossible to tell if it was the electrolytes, the sugar, or the water in the Gatorade that helped subjects last longer before cramping.
Other studies have shown that Gatorade and most other sports drinks don’t have enough electrolytes to make a significant impact on your blood electrolyte levels. Furthermore, your body is actually pretty strict about making sure its electrolyte levels don’t change too much. Other studies have shown that consuming a bunch of electrolytes doesn’t often change your blood levels of electrolytes.
This study does indicate that dehydration might contribute to muscle cramps, but it certainly isn’t the only cause and probably isn’t the main one. Based on this data and more like it, researchers realized that electrolyte depletion and/or dehydration are probably not the only or primary causes of muscle cramps. They needed to create a new theory.
In 1997, professor Martin Schwellnus and his colleges at the University of Cape Town reviewed the literature on muscle cramping and concluded there was not enough evidence to show muscle cramps were caused by electrolyte disturbances or dehydration. They proposed a new theory, that muscle cramps are a result of dysfunctional reflex control of the motor nerve as a result of fatigue. In layman’s terms, this means that when your muscles get tired, they become hypersensitive and twitchy, which causes them to cramp.
The exact mechanisms of how this happens are a bit complex and not super relevant, so here is the summary. There are two primary reflexes that your body uses to protect your muscles: the muscle spindle reflex and the Golgi tendon organ reflex. The muscle spindle is a small structure in each muscle fiber that makes sure you don’t overstretch a muscle. When it becomes activated, it tells your brain to forcefully contract your muscle to protect it. The Golgi tendon organ is another structure in each muscle fiber that does the opposite. When it’s activated, it tells your brain to relax the muscle to make sure it doesn’t contract too hard and hurt itself or surrounding tissues.
There is some evidence that when your muscles become fatigued during exercise, these reflexes get disordered. Your muscle spindles are over-activated and your Golgi tendon organs are under-activated. This causes your muscle to spasm, causing a cramp. This muscle fatigue hypothesis makes sense in light of six observations.
1. The most active, i.e., tired, muscles are those most likely to cramp. As we covered a second ago, if dehydration or electrolyte loss caused muscle cramps, you would expect more muscles to cramp.
2. Muscles that cross two joints are more likely to cramp. They also have higher muscle spindle activity. For instance, when you’re swimming, you point your toes down, which means your calf is shortened and already contracted. It becomes tired and even more likely to cramp.
3. Cramps usually occur in racing, not training, when athletes push themselves harder than they are used to. Cramps also tend to occur at the end of the race, when the muscles are most fatigued. Now, this could also be when they’re most dehydrated, but as you learned a second ago, the athletes who are most dehydrated have a lower risk of cramping.
4. Athletes who start their races too fast are more likely to cramp. Basically, excessive effort and fatigue, rather than electrolyte levels or dehydration, are associated with cramping.
5. Studies have shown that after Ironmans and marathons, the athletes who cramped had higher alpha motor neuron activity, which is a sign there was more of a signal from the brain telling their muscles to contract.
6. A 2011 study on marathon runners found that those who cramped had more muscle damage before the race and had a history of cramping.
Based on these six points and a few more technical ones that we don’t need to cover, it seems more likely that muscle cramps are caused by fatigue rather than electrolyte depletion or dehydration, or at least the fatigue is the dominant cause.
Before we get excited and start pouring Gatorade and salt tablets down the toilet, or accusing these companies of orchestrating some giant conspiracy to sell their stuff, we have to remember that none of this evidence is perfect. We don’t have a great way of creating muscle cramps in a controlled environment, so it’s still possible that electrolyte loss and dehydration may partly contribute to cramps; however, it probably is not the main reason and may not be a reason at all.
And now, the moment you’ve been waiting for. How to avoid and treat muscle cramps. Based on this evidence, there are two tips I can give you to prevent muscle cramps:
1. Specific training. Most evidence indicates that cramps are caused by fatigue. Martin Schwellnus, the researcher who created the fatigue model of exercise cramps believes that, “The key to prevention of exercise-associated muscle cramping is to reduce the risk of developing premature muscle fatigue.” Perhaps the best way to avoid fatigue is to train specifically for your competition and hard training sessions.
One study also found that people who are more likely to cramp generally have weaker muscles. You may also want to scale back the intensity or duration of the workouts that cause you to cramp and then gradually build your volume and intensity back to give your body more time to adapt.
2. Stay hydrated. While there isn’t strong evidence that dehydration causes muscle cramps, it may contribute mildly and it certainly won’t hurt you to stay hydrated. However, if you do cramp, it’s unlikely that not drinking enough was the cause.
With prevention out of the way, here are two tips to treat muscle cramps once they have occurred:
1. Rest. When you have stopped exercising or reduced your pace, cramps usually go away. You may have to stop for a few minutes for them to disappear.
2. Stretching. Stretching is actually one of the most scientifically backed treatments for exercise related muscle cramps. A 2010 review published in the journal of sports health concluded that passive, light stretching of the cramping muscles helps reduce the electrical activity of the muscle, thus helping it relax. By stretching, the researchers mean light stretching, not power yoga. You also only need to stretch for a few seconds. Stretching is also only a treatment. Another review published in 2010 found no evidence that stretching helps prevent muscle cramps.
3. Okay, so I lied. I have three tips for stopping muscle cramps. Pickle juice. Some limited research shows that drinking pickle juice may help trick your brain into relaxing cramped muscles. If you’re interested in exactly how to use pickle juice to help stop muscle cramps and what dosage you should take, be sure to listen to the last podcast, which you can find at www.impruvism.com/pickles.
We covered a lot today, so let’s recap briefly.
Most people think muscle cramps are caused by sweating out electrolytes and losing water, but multiple lines of evidence indicate this is not true. Dehydration may contribute to muscle cramps but there is almost no evidence that electrolyte disturbances cause muscle cramps. Most evidence indicates cramps are caused by fatigue. The best way to avoid muscle cramps are to train adequately for your competitions or hard workouts, build your training load gradually, and stay hydrated.
To treat a muscle cramp, you should rest, lightly stretch the muscle, and if you want to try something a bit different, drink some pickle juice.
If you want to read some of the studies you learned about today and do your own research, or you want links to anything else I mentioned, you can find everything on www.impruvism.com/cramps.
If you’re interested in more of the history of cramping research and the more scientific of the mechanisms behind cramping, you should check a three part series by Dr. Ross Tucker and Dr. John Dugas of www.sportsscientists.com. They have both conducted studies in this field and they can tell you far more about muscle cramps than I can. Their site is always full of great information, too. You can find links to that series at www.impruvism.com/cramps as well.
Speaking of great information, I want to know what you thought of this podcast. Did you enjoy it? Did it improve your life in any way, shape, or form?Did it make you smile and see rainbows? If so, please leave a review on iTunes. Thanks so much and I’ll see you next week for another awesome show.
1. Miller KC, Stone MS, Huxel KC, et al. Exercise-Associated Muscle Cramps. Sports Health. 2010;2(4):279–283. Full Text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3445088/
2. Sawka MN. Physiological consequences of hypohydration: exercise performance and thermoregulation. Med Sci Sports Exerc. 1992;24(6):657–670. Abstract: https://pmid.us/1602938 | Full Text: NA
3. Schwellnus MP, Nicol J, Laubscher R, Noakes TD. Serum electrolyte concentrations and hydration status are not associated with exercise associated muscle cramping (EAMC) in distance runners. Br J Sports Med. 2004;38(4):488–492. Abstract: https://pmid.us/15273192 | Full Text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1724901/
4. Brouns F, Beckers E, Wagenmakers AJ, Saris WH. Ammonia accumulation during highly intensive long-lasting cycling: individual observations. Int J Sports Med. 1990;11 Suppl 2:S78–84. doi:10.1055/s-2007-1024858. Abstract: https://pmid.us/2361783 | Full Text: NA
5. Sulzer NU, Schwellnus MP, Noakes TD. Serum electrolytes in Ironman triathletes with exercise-associated muscle cramping. Med Sci Sports Exerc. 2005;37(7):1081–1085. Abstract: https://pmid.us/16015122 | Full Text: NA
6. Schwellnus MP, Drew N, Collins M. Increased running speed and previous cramps rather than dehydration or serum sodium changes predict exercise-associated muscle cramping: a prospective cohort study in 210 Ironman triathletes. Br J Sports Med. 2011;45(8):650–656. doi:10.1136/bjsm.2010.078535. Abstract: https://pmid.us/21148567 | Full Text: NA
7. Jung AP, Bishop PA, Al-Nawwas A, Dale RB. Influence of Hydration and Electrolyte Supplementation on Incidence and Time to Onset of Exercise-Associated Muscle Cramps. J Athl Train. 2005;40(2):71–65. Full Text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1150229/.
8. Schwellnus MP, Derman EW, Noakes TD. Aetiology of skeletal muscle “cramps” during exercise: a novel hypothesis. J Sports Sci. 1997;15(3):277–285. doi:10.1080/026404197367281. Abstract: https://pmid.us/9232553 | Full Text: NA
9. Schwellnus MP. Muscle cramping in the marathon: aetiology and risk factors. Sports Med. 2007;37(4-5):364–367. Abstract: https://pmid.us/17465609 | Full Text: NA
10. Schwellnus MP. Cause of exercise associated muscle cramps (EAMC)–altered neuromuscular control, dehydration or electrolyte depletion? Br J Sports Med. 2009;43(6):401–408. doi:10.1136/bjsm.2008.050401. Abstract: https://pmid.us/18981039 | Full Text: NA
11. Schwellnus MP, Drew N, Collins M. Muscle cramping in athletes–risk factors, clinical assessment, and management. Clin Sports Med. 2008;27(1):183–94– ix–x. doi:10.1016/j.csm.2007.09.006. Abstract: https://pmid.us/18206574 | Full Text: NA
12. Schwellnus MP, Allie S, Derman W, Collins M. Increased running speed and pre-race muscle damage as risk factors for exercise-associated muscle cramps in a 56 km ultra-marathon: a prospective cohort study. Br J Sports Med. 2011;45(14):1132–1136. doi:10.1136/bjsm.2010.082677. Abstract: https://pmid.us/21402566 | Full Text: NA
13. Khan SI, Burne JA. Reflex inhibition of normal cramp following electrical stimulation of the muscle tendon. J Neurophysiol. 2007;98(3):1102–1107. doi:10.1152/jn.00371.2007. Abstract: https://pmid.us/17634341 | Full Text: https://jn.physiology.org/content/98/3/1102.long
14. Mauskop A. Assessment: symptomatic treatment for muscle cramps (an evidence-based review): report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Neurology. 2010;75(15):1397–author reply 1398–9. doi:10.1212/WNL.0b013e3181f003be. Abstract: https://pmid.us/20177124 | Full Text: https://www.aan.com/globals/axon/assets/6904.pdf