What Causes Exercise Induced Cramps? Not what you think.

Cramps aren’t caused by sodium loss and dehydration (but make sure you replace your sodium and stay hydrated)  

Muscle cramps are the enemy.   Just when you were having a great race, on your way to a PR, and pushing your limits like never before, you get a cramp that forces you to slow down, or may leave you unable to continue.   Athletes have likely been searching for the exact cause  of  (and thus a way to prevent) exercise associated muscle cramps (EAMC) since before the Olympic games in ancient Greece, but the fact is that we still don’t fully understand the mechanism  that causes cramps.   One thing we can be sure of, or as sure as we can be of anything proven by science, is that muscle cramps are not caused by electrolyte depletion or dehydration.

 

 

This seems counter-intuitive to many,  the notion that cramps are caused by dehydration and electrolyte depletion has been around for a long time and has been  repeated so many times that it many simply accept it as fact.  This is probably because athletes that suffer cramps are frequently drenched in sweat and covered in salt, so there does seem to be some anecdotal evidence for the correlation.   However the fact is that there is no known mechanism by which sodium depletion or dehydration would cause cramps.   Additionally, there is little evidence to support the theory that the loss of sweat is actually responsible for the EAMC, and a large amount of evidence to refute it.     A quick search of the scientific literature generates several studies that show essentially no difference in the water or electrolyte losses of athletes that cramp, vs those who don’t cramp .      The research of the last decade or so has led to an acceptance among exercise researchers that electrolyte loss and dehydration are not the cause of EAMC.    But if losses due to sweat aren’t responsible for cramps, then what is the culprit?

 

 

The current school of thought is that cramps are primarily due to “altered neuromuscular control” due to fatigue.   While studies have shown that water and electrolyte losses are NOT associated with cramping, there are several factors that are definitely associated with EAMC, including lack of fitness, pre-race muscle fatigue   and athletes simply pushing themselves harder than usual.    The simple and effective treatment of stopping to rest and stretching the muscle likely gave researchers some of the first clues that dehydration was not the cause of cramps.  After all, stretching and rest does nothing to help with hydration or electrolyte levels.  The altered neuromuscular control theory truly began to take hold in 1996, and the evidence for theory has grown, as has the evidence against the dehydration/electrolyte theory.  There are a few different plausible theories for exactly how this “altered neuromuscular control” causes cramps, and as is typical, more research needs to be done. But the point is that there is a mountain of evidence to show that electrolyte depletion/dehydration is out, and general fatigue is in.

 

 

Does that mean you should skip the electrolyte beverage?   Absolutely not.  The American Dietetic Association, The American College of Sports Medicine, and Dieticians of Canada all recommend a carbohydrate/electrolyte beverage during prolonged exercise.  Dehydration due to lack of fluids, and hyponatremia due to sodium loss can be not only detrimental to performance, but deadly. So I recommend that all my athletes use a carbohydrate/electrolyte drink during all rides longer than an hour.   The most important thing about one of those beverages is that you like the taste and you’ll dink it.   It isn’t doing any good just sitting in your bottles, it has to find its way into your stomach.  I’m sponsored by Powerbar and I enjoy the taste of their lemon-lime Ironman Perform, so that’s what I put in my bottles, and in my stomach.   The carbohydrates and the electrolytes will help replace what you use and what you use.   But they won’t protect you from cramps.

It won’t keep you from cramping, but drink it anyway.

Bonus:   Some people have asked me about pickle juice to prevent cramps.  There is actually some strong evidence that pickle juice can help relieve cramps, and while researchers have typically used juice from a plain old jar of dill pickles, companies have been quick to sell pickle juice that is specifically marketed and packed for endurance athletes.  Pickle juice is high in sodium, but it does not appear to be the sodium that helps with the cramps.  The pickle juice works so rapidly, that the sodium does not have time to enter the stomach and then the bloodstream.  The most likely theory is that the acidity of the vinegar has an effect on the nerves at the back of the throat that somehow blocks the cramps.  As is typical more research is needed to determine the exact mechanism.

I’ll buy a bottle that also comes with the pickles!

 

Sean is the head coach for Crank Cycling in San Diego CA.   Have a question for Sean or a topic you would like to see covered?   Contact Sean Via his website: CrankCycling.com

 

 

References:

 

1)Med Sci Sports Exerc. 2005 Jul;37(7):1081-5. Serum electrolytes in Ironman triathletes with exercise-associated muscle cramping. Sulzer NU1, Schwellnus MP, Noakes TD.

 

2) Br J Sports Med. 2004 Aug;38(4):488-92. Serum electrolyte concentrations and hydration status are not associated with exercise associated muscle cramping (EAMC) in distance runners. Schwellnus MP1, Nicol J, Laubscher R, Noakes TD.

 

3)Br J Sports Med. 2011 Jun;45(8):650-6. doi: 10.1136/bjsm.2010.078535. Epub 2010 Dec 9. 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.Schwellnus MP1, Drew N, Collins M.

 

4)Br J Sports Med. 2009 Jun;43(6):401-8. doi: 10.1136/bjsm.2008.050401. Epub 2008 Nov 3.Cause of exercise associated muscle cramps (EAMC)–altered neuromuscular control, dehydration or electrolyte depletion? Schwellnus MP.

 

5)Sports Med. 2007;37(4-5):364-7.Muscle cramping in the marathon : aetiology and risk factors. Schwellnus MP. J Athl Train. 2009 Sep-Oct;44(5):454-61. doi: 10.4085/1062-6050-44.5.454.

 

6)J Athl Train. 2009 Sep-Oct;44(5):454-61. Electrolyte and plasma changes after ingestion of pickle juice, water, and a common carbohydrate-electrolyte solution. Miller KC1, Mack G, Knight KL.

 

7)J Am Diet Assoc. 2000 Dec;100(12):1543-56.  J Am Diet Assoc. 2000 Dec;100(12):1543-56. Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance.