Sunday, August 2, 2015

What Causes Muscle Cramps?

Picture by Jon Candy from Flickr
A patient came in to see me yesterday and complained  that if not for a muscle cramp near the end of her recent race, she would have won her age group and also gotten a personal best timing.

After putting it up on Facebook, she had many, many unsolicited comments : Eat bananas, take salt tablets, drink Gatorade, have some pretzels. Knowing that I used to race, she wanted to know my thoughts and get some advice on how not to cramp during a race.

While her friends and even strangers who posted on her Facebook page meant well, none of their advice will help her as even expert exercise physiologists can't say for sure what causes exercise induced cramps.

The most common and popular theory on cramps is that they are caused by sodium (or salt) loss and dehydration. Fluid and electrolyte loss. This has been the focus of much Gatorade (or other companies) sponsored research. More on that in another post definitely.

Tim Noakes, possibly the most renown sports scientist on this topic found no significant differences in sodium and magnesium levels of 72 ultra marathoners between those who cramped and those who didn't cramp. There was no differences in body weight, plasma (or blood) volume between the two groups, showing that dehydration had no real effect on cramps.

Dehydration could however hasten muscle fatigue. And this is what Noakes and most exercise scientists believe is the likely cause of cramps.

In the above ultra marathoner study, 100 percent of the runners cramped in the last half of the race or right after the race. Think about it, when was the last time you had a muscle cramp? At mile 20 (or 32 km) in a marathon or after 3 km in a 5 km race?

This explains why cramping is most likely to occur during races than training. You tend to start off too fast or you pushed yourself too hard. Other studies have found that tough, hilly course and poor pacing (starting too fast) are predictive of muscle cramps.

So, anything you can do to prevent muscle fatigue should then help to prevent cramps. The obvious though undesirable strategy is to simply slow down. Not exactly what you would want to hear or read!

Since guarding against muscle fatigue is key, you can't take any short cuts in training. Train more, do longer distances. You simply have to adapt to the distance you want to race. There is no substitute for strength work that is running specific. Gotta love hills and speed work.

Plyometrics (or explosive exercises) may improve the endurance of the receptors in your muscles that are thought to cause muscle cramps.

Knowing your own capabilities is key as you can choose a pace right from the onset of the race. Cramps are more likely to happen to athletes who start too fast.

"That's it"? My patient said. Yes, that's it.


Schwellnus MP, Nichol J, Laubscher R and Noakes T. (2004). Serum Electrolyte Concentrations And Hydration Status Are Not Associated With Exercise Associated Muscle Cramping (EAMC) In Distance Runners. BJSM. 38: 488-492. DOI: 10.1136/bjsm.2003.007021.

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