Cramps

A new study suggests that cramps during exercise have nothing to do with electrolytes or dehydration, but are simply due to muscle fatigue.8479719962_3208ac3c1e

For decades we have been told that cramps during long runs are due to dehydration and loss of electrolytes. It is tempting to think so indeed, as patients with disturbed electrolytes due to illness suffer from cramps. However, these patients are usually severely ill and have cramps all over their bodies. Runners on the other hand, typically have them in the working muscles and often only later in the race. Moreover, they might be tired but they are not ill!

Scientists now suspect that cramps in runners (or in any athlete) might be something different. Indeed, there is more and more evidence that cramps are due to muscular fatigue, and the latest study by Martin Hoffman and Kristin Stuempfle suggests this as well.

They studied 280 runners during a 161 km ultra-marathon by measuring their body weight before, during and after the race, and they determined their sodium and CK (= a measure of muscular damage) levels by a blood sample after the race. The runners also completed a questionnaire about cramping, “near” cramping (= controllable, not full blown), drinking strategies and the use of electrolyte supplements.

14% of the participants reported cramping, and 28% near cramping. There was no difference in changes in bodyweight or sodium levels between those suffering from cramping or near cramping and the others. Those who cramped or near cramped however, showed higher CK blood concentrations and were more likely to have suffered from them in the past.

The researchers concluded that cramping was associated with muscle damage, which confirms other studies suggesting that it is due to fatigue.

This is important for all of us, because if they are right, there is no need to take electrolyte supplements. It could then be more beneficial to review our training, build up our muscle strength and see if our technique needs improving.

References:

KW Braulick, KC Miller, JM Albrecht et al. Significant and serious dehydration does not affect skeletal muscle cramp threshold frequency. Br J Sports Med. 2013; 47(11): 710-4.

MD Hoffman and KJ Stuempfle. Muscle cramping during a 161 km ultra-marathon: comparison of characteristics of those with and without cramping. Sports Med Open. 2015; 1 (1):8.

MP Schwellnus, EW Denman and TD Noakes. Aetiology of skeletal muscle “cramps” during exercise: a novel hypothesis. J Sports Sci. 1997; 15(3):277-85.

MP Schwellnus. Cause of exercise associated muscle cramps (EAMC) — altered neuromuscular control, dehydration or electrolyte depletion? Br J Sports Med. 2009; 43(6):401-8.

 

Picture: photo credit: <ahref=”http://www.flickr.com/photos/25874444@N00/8479719962″>The Donadea 50KM Ultramarathon Race 2013</a> via <a href=”http://photopin.com”>photopin</a&gt; <a href=”https://creativecommons.org/licenses/by-sa/2.0/”>(license)</a&gt;

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4 thoughts on “Cramps

  1. Sounds completely plausible. My left calf was “near cramping” in the last 5k of the bike portion of my half ironman. Once I finished the bike and started to run I was no longer using my calf muscles the same way and was able to run the half marathon run portion without any further issues. I weighed the same after the race as before so nutrition & dehydration wasn’t the issue – lack of adequate bike training and muscle fatigue is much more likely.

  2. That’s certainly plausible, particularly given the fact that it is the working muscles that cramp, not diffuse cramping. Did they look at potassium as well? That’s the one I hear most frequently blamed for cramping even though clinically you have to get incredibly low potassium (lower than anyone with healthy kidneys and reasonable diet could feasibly get to) in order for that to happen.

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