Wednesday, April 30, 2008

Hot and Bothered

It's that time of the year again. Running Saturday's Promise Land 50k in 75-degree "heat" affected almost every runner I talked to. In three months, 75 degrees will feel cool -- thanks to the wonderful world of heat acclimation. But as summer waxes toward its dog days, we will need to deal with the heat.

I read recently in the book "Run Less Run Faster" that our running performance degrades 1-2% for each 1.5 degrees F over 60. That means that in Saturday's 75-degree heat, we were facing a performance degradation of 10-20%. That's pretty serious, and it's only 75-degrees! Check out what happens as the mercury rises.

When it is 100 degrees three months from now, we will be running at 50%! Last year at Mike Day's informal gathering he calls the Sweaty Butt 50k, we ran in temperatures in the high 90s. After 20 miles we all got smart and called it quits. This year he is starting the event earlier in the day, and he told me that if it is very hot he will once again give runners the option to cut it short.

Heat acclimation plays a big role in all of this. Surely come August, running in 75 degrees will seem much easier than it did on Saturday. But will it still suffer from a 10-20% degradation in performance? Acclimation allows our bodies to better deal with the heat. says:

When humans move from a cool or temperate environment to a hot, dry desert environment or vice versa, they should spend up to seven days acclimatizing to the change in their environment. This lets the body make internal adjustments (see homeostasis) to compensate for the change in environment conditions. If the acclimatization process is ignored, then the person is at higher risk for heat related injuries (heat stroke, heat cramp, pneumonia).

So our performance will improve as the temperature stabilizes.

And we all know that dehydration plays a role too. I've read in many places that our performance degrades with even slight dehydration. The jury is out on this one as new research is coming out and old research is turning out to have been funded by a company with a lot to profit. Check out Mike's recent post on hydration to learn more about this.

It turns out less might be more after all, says the "endurance running hypothesis," or the belief that human evolution has programmed us to run (a trend that is clearly reversing in my son's generation).

"Humans evolved not to drink much at all during exercise," says Dr. Timothy Noakes, chairman of exercise and sports science at the University of Cape Town (and author of one of the most informative running books ever). "If they had to stop every 5 minutes to drink, they would never have caught the antelope." He goes on to say that "the best runners in any culture are the ones who run the farthest and drink the least." Noakes' recommendation is to drink just enough to satisfy or minimize thirst. (source: Men's Health, May 2008)

I'll drink to that.

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