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Coaches Blog

Heat Acclimating 101 For Endurance Athletes

Summer racing season is upon us. That means training and competing in heat and humidity is practically inevitable. Some athletes adapt well to the heat, and others struggle to achieve peak performance.

Many endurance athletes plan for practically everything on race day–except the heat. Coupled with a strategic hydration and nutrition plan, taking the time to acclimate to heat and humidity can really save you from “burning up” before the finish line.

What is heat acclimation?

Heat acclimation is the process of improving your body’s tolerance to heat during exercise. It comes from gradually increasing the intensity or duration of your workouts in a hot or humid setting.

If you live in a cooler climate, it will take a bit of strategy and intentionality to prepare your body to race in a hot or humid environment.

How heat and humidity affect your body

When training or racing in the heat, the first thing you’ll notice is that your heart rate zones will change. Hotter and more humid conditions lead to an increase in heart rate caused by lower blood flow. Your lactate concentration will also increase because you’ll be performing in a higher heart rate zone at much lower speeds.

You’ve probably noticed that you turn red when exercising in the heat. That’s your body drawing blood away from your muscles to cool your skin. Because it takes a lot of energy to cool your body, you’ll burn more glycogen as energy. Bigger athletes will need more glycogen for this cooling process.

In short, your body is working harder and burning more glycogen to keep you cool. The good news is that you can train your body to handle hot, humid conditions, but it requires some strategic preparation.

How heat acclimation impacts your body

The human body is incredibly adaptable. With enough acclimation, your body becomes more efficient at sweating, which lowers the temperature at which you start sweating. Your body also learns to reduce the amount of electrolytes you lose in sweat and even changes the size of your sweat glands.

That means people who produce a lot of watery sweat just have good physiology–remember that next time you’re trying to cover up nervous sweat stains at your next presentation!

With all the physiological changes your body goes through to adapt to the heat, there’s some evidence that high-heat acclimation can help with performance at altitude.

Heat Acclimation Training Strategies

Whether you’re prepping for the Badwater Ultra, the Garmin Outbound, or a hot IRONMAN race, heat acclimation is a factor you’ll want to consider. Here are some practical ways to incorporate heat training into your preparation.

DIY heat training strategies

Many athletes simulate racing in heat by training during the hottest parts of the day. Rather than going for a morning run, hit the pavement at 4pm. If the temps still aren’t warm enough, add a layer or two of clothing.

Many athletes set up their trainers in the laundry room if they’re preparing for a hot race during winter. Turn on the dryer and run it for a nice blast of heat and humidity. (Plus, we all know endurance athletes are always doing a load of laundry.)

Another DIY approach is to buy one or two space heaters and a humidifier to put around your turbo trainer and treadmill. Olympic medalist, Katie Zaferes, prepared for the oppressive Tokyo heat by setting up a DIY “hot box” in her garage with a plastic tent and some space heaters.

Saunas and dry saunas can also be helpful in heat acclimation. Incorporate them into your training routine if you have access to these resources.

Factors to consider when heat acclimating

Stress: Any heat training will add extra stress to your overall training. Talk to your coach about ways to reduce the training intensity appropriately, so you don’t overload your body during the acclimation process.

Heat acclimation timeframe: While everyone’s a bit different, it typically takes at least seven to ten days of heat exposure in a row to begin to see positive physiological adaptations. So, consistency is essential (as with many things in endurance training).

Once your body acclimates to the higher temperatures, you can usually maintain that adaptation by continuing with heat exposure once every three days or so. One positive thing is that if you’re traveling to a hot environment, you can generally reacclimate (rebuild your recent heat acclimation) in as little as four days.

Avoid excessive air conditioning use: Avoid a lot of air conditioning and cool rooms during your heat acclimation period and the days leading up to the hot race. This can negate the effects of heat acclimation.

Reducing heat and humidity impacts

Whether you’re well acclimated to the heat or not, these steps can help keep you a bit cooler and protected from the effects of heat and humidity during training and racing.

  • If applicable, choose a bike helmet with plenty of ventilation. In many cases, it’s worth having more ventilation than aerodynamics because your body functions at a higher level when it’s cooler.

  • Know your sweat rate and adjust your water and electrolyte intake accordingly.

  • During races, take time to put ice around your head and on your torso. Many athletes notice the benefits of keeping ice near their hearts and in their hands. Thorbjørn Sindballe is a Danish triathlete known for wearing white gloves, which he kept filled with ice during his IRONMAN racing career.

  • Wear a hat and long-sleeved cooling tops or arm coolers. These offer protection from the sun as well as better cooling through evaporation.

Whether you’re a distance runner, triathlete, or cyclist, endurance athletes must learn to adapt to unique racing and training conditions. You’ll learn how your body responds to different conditions and the best strategies to set yourself up for a great race with practice.

An experienced, knowledgeable coach is a valuable asset when preparing for hot and humid racing conditions. They can adapt your training plans appropriately, incorporate heat acclimation strategies, and help you adjust your nutrition and hydration plans.


Gregg Edelstein is a certified USA Triathlon Level 1 Coach, an IRONMAN University Certified Coach and a USA Cycling Level 3 Coach based in the greater Boston area. Gregg offers his athletes insight on the principles of exercise, nutrition, sports psychology, and injury prevention, working to make them well-rounded and engaged athletes that share his passion for sport. Gregg can be reached at


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