You Can’t Beat the Heat by Avoiding It

All summer long I’ve been reading the social-media complaints of so many runners this summer about the heat and humidity! But now, the sun is rising later and setting earlier. August is over. September is coming. That means autumn is coming too – in about 23 days! If you haven’t figured it out by now, you have a very short time left to reap the benefits of “heat acclimatization.”

The common phrase is “beat the heat”. But when most people say that, they mean ‘stay inside in the air conditioning.” I like to beat the heat by meeting it head on. During the week, I run around noontime – all year long. But aside from that typical late-April heat wave, the heat doesn’t bother me. Don’t get me wrong, it does wreak havoc on my performance; that’s just plain physics. But by taking advantage of heat acclimatization (i.e., running at noon every day as spring turns into summer) I don’t mind being out in the heat of an August afternoon. I’m also looking forward to the aftereffects, as the days cool off and I still have the superpowers I built up during the summer.

Super powers? Do I have your attention now? OK, science time! Heat acclimatization is the adaptation of your body in response to heat stress in a natural environment. These adaptations include reductions in heart rate, body temperature response, skin temperature response, and perceived exertion. These adaptations also include increases in sweat rate, sweat onset, cardiovascular function, and overall ability to perform in the heat.

You become a better sweater: You start to sweat sooner, and you sweat out more. Also, the sodium content of your sweat decreases, which helps prevent dehydration. The result of better sweating? Better cooling!

Your cardiovascular function improves: Your body develops an increase in plasma volume, improved blood flow, a decreased heart rate, and an increased blood volume per heartbeat. What’s the point of all this? When you exercise in the heat, there are two conflicting duties for your blood: 1) oxygenate the muscles; 2) dissipate heat from the skin. Obviously, when you are exercising in the heat, your need for both increases. With an increased blood volume, your heart has more blood to pump around your body so it can do both of these better at the same time.

The good news: if you exercise for about an hour a day in the heat, it takes an average of two weeks to acclimatize.

The bad news: heat acclimatization goes away just as fast (or faster) than it arrives after the stimulus of training in the heat is gone.

More good news: Imagine for a moment your body all hopped up on heat acclimatization, and suddenly it’s no longer that hot. If you time it right, you will still have all those cardiovascular benefits when its time for those key fall races! Training for a spring or summer race during the winter? Trick your body into early heat acclimatization by over-dressing so that you’re very warm even though the weather is still cool.

Finally – be smart! Don’t start by going out in the noon heat to get acclimatized! You’ve got to work up to it. Start off during the cooler parts of the day and gradually work up to full heat. And stay properly hydrated and electrolyted. Weigh yourself nekkid before and after your exercise; for each ounce of weight lost, drink an ounce of water. And dress for the weather in wicking, technical fabrics.

You’ve got three weeks until autumn arrives. Let’s see if you can head into fall with a full supply of heat acclimatization!

Here are some scientific references if you are so inclined:

https://www.sportsci.org/encyc/heataccl/heataccl.html