Heat Adaptation: Training for a Hot Race

Pouring ice over your head isn’t the only way to deal with a hot race.

Summer is here and sunny days and warm temperatures make most of us smile as we dig out sunscreen and tank tops and stow away our tights and gloves. The bad news? If you have a race planned soon you might be dreading the potential of a scorcher on your big day. As Pumpkin reported in her Fargo Marathon Race Recap, hot conditions took a serious toll on her both physically and mentally. Racing in the heat, especially unanticipated heat, can have a huge impact on our performance.

The negative effect of heat on running performance can be significant: “There is a great deal of empirical data showing a link between ambient temperature and performance … performance impairments of 1.6 to 3 percent in marathon times for every 10 degrees above 55 degrees Fahrenheit. The effect seems to be less dramatic for faster runners” (Henderson, “Heat Performance and Acclimation”). Aside from discomfort, heat causes problems during training and on race day because it sends blood to the skin to cool us down, diverting it away from our muscles, and by causing dehydration, which also inhibits performance.

The good news? We can actually train our bodies to acclimate or adapt to the heat to decrease the negative effects it has on our training and racing.

The Quick and Dirty Science Lesson

Blood is made up of four constituents: red blood cells that are responsible for carrying oxygen, white blood cells that fight disease and infection, platelets that aid in clotting, and the liquid part of our blood, plasma, which is 90% water. Plasma suspends all the cell parts of our blood along with electrolytes and proteins and plays a crucial role in our body’s temperature regulation. The cooling process occurs when blood leaves our muscles and is diverted to the skin so the water portion of our blood can evaporate to bring down body temperature. The red blood cells, unfortunately, just have to come along for the ride. This means that we can improve the problem by increasing our plasma volume; this is what naturally happens as we adapt to heat. The goal of heat adaptation is to increase our total plasma volume.

The Observable Truth

Heat adaptation, while relevant any time we are training for a race that has the potential to be warm, can be especially important for spring races when you have trained over the winter, often through miserable and cold conditions only to be faced with 70+ degree weather and extreme humidity come race day. In contrast, by nature of timing, simply training through the summer can aid in heat adaptation process for hot fall races. Regardless of the timing, there are things we incorporate into our training to help us adapt to the heat and prepare for a hot race.

How to Adapt

Train Hard. All endurance training, but especially high-intensity training, makes us more fit and increases plasma volume. Intense workouts can suck, but they are in your training plan for a good reason! Heat adaptation is important not only for improving your overall fitness and speed, but also helping you adapt to high temperatures. Keep those Yasso 800’s in!

Train in higher temperatures. With just 21 days of training at a higher temperature, total plasma volume increases and other physiological changes occur including decreases in perceived exertion, training heart rate, and core resting temperature. These all affect the real and perceived effects of heat on performance. A sample of a heat adaptation workouts might be doing your tempo runs at a gradually increasing temperature starting at 95 degrees and working up to 113 degrees (always consult a doctor before beginning any training plan, but especially one that will require this type of physical stress).

I’m sorry, Cilantro, I just can’t let you do that.

Training in heat chambers. Heat chambers are places where you can practice light or moderate cardio in high temperatures. Those who don’t have access to fancy medical and sports facilities with specifically designed heat chambers can achieve similar benefits in sauna or steam rooms. Seven to ten days prior to a hot race, spend an hour in a sauna or steam room depending on your race environment. (Dry & hot race: Sauna; hot & humid race: Steam room). It is important to use heat chamber training immediately preceding the race because the effects will decay after only a week of non-heat exposure. The key here, however, is that this is often when one is tapering for a big race like a marathon, and the heat training might decrease the benefits of the taper. Because of that, heat training needs to be used for specific races and with careful attention paid to overtraining.

Train in layers. For at least some of your runs, train at the hottest part of the day, wearing layers. This seemed to be popular with elite athletes who ran in the unforgiving LA sun at the Olympic Trials Marathon this year. This is much easier than finding access to a heat chamber, and is perhaps more convenient than taking extra time to sweat it out in a sauna or steam room.

Practice fueling and hydrating. While working with heat adaptation methods above, practice fueling and hydrating in those conditions. Dehydration and a diverted blood flow can affect how your body processes fuel and water. Practice will help you to see what you can and cannot eat and adapt your fueling/hydration schedule so your performance isn’t negatively impacted by GI issues in addition to the side-effects of running in the heat.


If you missed it, this might remind you a little of Clove’s training for Badwater last year. While you don’t have to go as extreme as she did, her training protocol was designed not only to get her ready to run a very long distance over an extended period of time, but also for the crazy temperatures she encountered.

Finally, it’s important to stress that both in heat adaptation and hot races, there are risks for dangerous heat illnesses including heatstroke and heat exhaustion. Monitor yourself carefully for the symptoms and back off or seek medical attention if these symptoms arise.

Have you ever trained specifically for heat? How do you prepare for a hot race day?

Ultrarunner, adventurer, academic, and feminist. Running Across the USA in 2021. I write about ultrarunning, adventuring, and the intersection of endurance athletics and life.

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  1. Great article! I can totally relate. I trained all winter in -20ºC-ish and come race day past May (Ottawa Marathon), you guessed it, heat wave! As a result, the race times were shifted and the marathon course was eventually closed (5h30+ were redirected). Practicing my fuelling throughout winter training really helped; I was used to drinking and taking gels on a regular basis. I ended up carrying a frozen water bottle during the race (it melted in the first 3K). Salt tabs have also helped me in the past.

  2. This is really interesting- especially the science behind it. Thank you for all the interesting ideas, will definitely keep this one filed away for the next time I need to train for a race in the heat! While I’ve never specifically done that before (maybe I should have!), I did find during the marathon trials in LA, that drinking a LOT more water than usual, as well as dumping entire bottles on my head, really helped. Unfortunately I didn’t start doing this until later in the race, but after doing that, I actually felt better the last lap then the entire race.

    1. A part of me thinks that just regular speedwork and intervals are the best way to do that (and usually built into most plan)! But I’m interested to try some hot hot yoga and see if that makes a difference even though it’s not ostensibly cardio.