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Published July 18 2011

Wagner: Cramping an unwanted part of running experience

FARGO - Earlier this month, after running a half marathon, a friend wrote to me looking for help.

Once again, he found himself in the latter stages of a race, struggling with cramps.

Thoughts flashed back to my own experiences, particularly at marathons in Fargo and Duluth. It was just this year, at the Fargo Marathon, when so many people struggled with cramps and heat-related issues.

It’s frustrating to put in months of training to find yourself unable to run as well as you hoped. And unfortunately there isn’t a lot of science to help explain cramping during exercise.

But there has been some research. Personal experience and experimenting also help to clear up some of the mystery, leading me to believe there are three main causes for cramps:

Heat and humidity: There’s some debate about the effect of heat, and whether it induces cramps, but there appears to be supporting evidence that high humidity, in combination with heat, is a primary factor in cramps.

One reason is that the body can’t effectively and efficiently cool itself under those conditions (the body burns fuel to cool itself, plus powering your muscles during running).

The combination of heat and humidity almost always leads to a high dew point, and that means the sweat doesn’t evaporate quickly or easily. And that’s important because it’s very difficult then to determine how much fluids you lose during exercise.

Fluids: In cool or moderate weather races, people often drink too much water, which then causes an electrolyte imbalance in the body. Of those who die running marathons, it’s rarely ever dehydration.

Instead, a pre-existing medical condition or hyponatremia (low sodium in body cells caused by drinking too much water) usually plays a major role. Usually, people drink too much water and they end up with dangerously low electrolyte levels.

Improper training: In some cases, cramps can be induced by running on a course that you’re simply not trained to do. For instance, someone who runs on mostly flat terrain often struggles, usually with calf cramps, on a hilly course.

That’s one reason you’ll hear marathoners simulate a race course in their training, although there’s other reasons to support that type of training.


Forum News Director Steve Wagner writes a running blog, which can be found online at http://runningspud.areavoices.com/.

He can be reached via email at swagner@forumcomm.com.