What is Heat Acclimatization and How Can We Use It in Training?

If you've been on a tropical vacation and spotted someone wearing a three-piece suit, looking cool as a cucumber, while you sweat away in your shorts and flipflops, you’ve probably wondered about heat acclimatization without even knowing it.

Brock Armstrong
8-minute read
Episode #379

In another study that focused on the effects of heat on gut more than on the muscles, they found that gradual exposure to repetitive exercise and non-exercise heat stress can improve heat transfer from core to the skin. It can also create more efficient cardiovascular function, decrease heart rate during hot exercise, decrease skin and body temperature during hot exercise, increase blood volume, and decrease electrolyte loss via kidney filtration.

Ok, one last study before we jump into the tips!

Researchers from the University of Otago in New Zealand enlisted elite rowers to row for five days for 90 minutes per day in a study from the European Journal of Applied Physiology on the effectiveness of short-term heat acclimation for highly-trained athletes. The catch was that they were rowing in a room that was 104°F and 60% humidity. They didn’t have to row hard, just hard enough to overheat them slightly.

In the end, there was a 1.5% increase in 2,000m rowing performance. Now keep in mind that these were pro rowers, not your man-on-the-street, so 1.5% is impressive. The researchers figured there were many reasons for this increase, most notably the 4.5% higher blood volume (which again is more impressive in a pro athlete than in an average person) plus an enhanced ability to mentally handle slight dehydration.

How To Heat Adapt

There are two ways to do this: passively and actively.

Passive Heat Adaptation

This involves hanging out in dry heat saunas or steam rooms, and although it induces the same cardiovascular and sweat changes as active heat training (which I will get into in a minute), it doesn’t require as much recovery or the embarrassment of dragging a stationary bike or kettlebell into the sauna.  

Both a sauna and a steam room have been shown to achieve solid results, so choose your favorite or go with whichever one you have the easiest access to. Begin with 10-15 minutes of passive heat training, and gradually build up to 45-minute sessions every two or three days.

Adaptations can occur within as few as ten days but if you’re using passive heat training for preparation for a race (like I did for Thailand), then start at least four weeks—or as many as eight weeks—before your big day.

Active Heat Adaptation

If you are going to be competing in the heat, then active heat training is the way to go.

You probably guessed that this one involves actually exercising in the heat. This can be done easily at home in a small room with a heater or humidifier under the bike or next to a treadmill. If you have access and won’t get your gym membership revoked, doing a workout in an actual sauna or steam room is even better.

You can do either a steady exercise (like jogging on a treadmill) or interval training (like a Tabata set on a bike). But remember, this is hard on you! Especially at first, so if you begin to get too hot and it becomes a struggle to continue to exercise comfortably, you will still get benefits and adaptations if you stop exercising (or turn off the heat). Allow your heart rate to slow and your body to cool, and then (if you are up for it) slowly get back into your workout. There is a cool name for this hot method of starting and stopping: controlled hyperthermia.

If you are going to be competing in the heat, then active heat training is the way to go. You truly need to experience the physiological and psychological responses to hot weather racing to be more than just good at sweating on the day. You will need to have hot weather grit.

Active training is certainly more uncomfortable but it will yield faster results than the passive heat adaptation. You will only need to do 45 to 60 minutes of moderate-intensity exercise in the heat for 7-10 consecutive days or four to five times a week for two to three weeks to see good results.

Here are some quick and dirty ways to acclimate:

  • You can entertain yourself or learn while you’re sweating by bringing a book (that you don’t mind getting wet or sweaty) or an mp3 player into the sauna while you are doing passive heat acclimation.
  • Do some low to mid-intensity workouts in the sauna or steam room. For example, you can bring a resistance band into the sauna and do side raises, bicep curls, front raises, leg raises, and planks and any other exercises that you can do without accidentally punching the walls—or other sauna goers.  
  • Or as I mentioned before, if you are exercising on a treadmill or bike trainer, keep the temperature turned up in the room and the doors and windows closed. If that isn’t good enough, bring a heater or humidifier in the room.
  • Or, like that study from the beginning of this article, put on some extra layers!

One word of caution, you will start to lose the positive adaptations of heat training in about seven days, so plan accordingly. If you are doing this training for a specific event or race, I would suggest continuing up to four days before the event.

No matter how acclimated you are, you will never be completely immune to the dangers of exercising in the heat.

Before we wrap up, I want to make sure you know that no matter how acclimated you are, you will never be completely immune to the dangers of exercising in the heat. So, if you are planning to compete seriously in a hot climate you still need to do the following:

  • Drink plenty of fluids.
  • Dress appropriately.
  • Avoid midday sun.
  • Wear sunscreen.
  • Wear clothing that breathes.
  • Dump water on your head and face.
  • And above all else, keep your wits about you!

The very last thing you want is to have a big race PR attempt cut short because of a face-plant that leaves your skin (and pride) on the hot Chicago asphalt on an unseasonably hot October morning.  

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About the Author

Brock Armstrong

Brock Armstrong is a certified AFLCA Group Fitness Leader with a designation in Portable Equipment, NCCP and CAC Triathlon Coach, and a TnT certified run coach. He is also on the board of advisors for the Primal Health Coach Institute and a guest faculty member of the Human Potential Institute. Do you have a fitness question? Leave a message on the Get-Fit Guy listener line. Your question could be featured on the show. 

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