The Power of Heat Training

This article was originally written for Dr. Kelly Starrett and Juliet Starrett’s The Ready State. You can read it, and many other similar articles at

Today is a special day. Today, I want to talk to you about one of the most powerful ways you can improve your training, your health, and your performance. Heat. 

Heat training, most often in the form of sauna bathing, has a ton of benefits for human biology. These range from endurance improvements in sport, to muscle mass and strength gain, and even to brain function, mood, and detoxification. 

However, heat training can be double edged. The event that kicked off years of chronic disease for me was a sauna session, undertaken immediately after a hard workout and at the end of months of constant exercise, sauna work, and an unforgiving schedule. Most likely you’ll never run into the problems I did, but it’s still worth treating the power of heat training with respect.

And that’s exactly what we are going to do with this article. 

Getting Lit

One of the first articles I ever wrote for The Ready State was called The Power of Cold Therapy, where I discussed the myriad benefits we can enjoy from getting into frigid environments. Turns out, humans have incredibly complex biology designed to deal with the cold, and when us modern men and women voluntarily expose ourselves, it has huge benefits for our health. Cold therapy increases brown adipose tissue (BAT,) which helps you burn fat and may lower your risk for diabetes. Cold indirectly results in higher calorie burning in rats, has been shown to increase insulin sensitivity in diabetic humans, and improve weight loss. That’s just the weight loss implications. 

This is a list of other benefits of cold therapy I pulled from my article (which I strongly recommend reading in conjunction with this one):

Cold is great, but it’s not the cold that is causing these benefits, per se. It’s our body reacting to the cold. 

True to form, our sophisticated and complex biology has a similar list of responses to the heat. Our bodies create unique proteins in response to high temperatures, known as “heat shock” proteins. These are entirely their own molecule, and are not the same as “cold shock” proteins, nor are their benefits. 

Heat shock proteins and other chemical responses result in specific and powerful responses to things like sauna sessions, high intensity workouts, training outdoors in the summer, and other tactics. 

Heat training is essentially any technique where heating up the body is used to access these benefits, of which there are many. Most of the things I’ll reference can be achieved using a Sauna, but there are other ways too. Infrared light, outdoor exposure, even hot baths are all powerful forms of heat therapy. 

Endurance Benefits of Heat Training

We’re going in strong with this one and starting with performance. 

Heat training is huge for workout performance, especially endurance. It’s been well shown that sauna sessions can increase blood volume. This results in a lower resting heart rate, and has similar effects to the illegal performance enhancing drug erythropoietin. Runners who used a sauna for 30 minutes after a run twice a week increased their run time to exhaustion by 32%. These improvements seemed to correlate closely with the observed improvements in blood markers such as increased red blood cell count.

Another interesting effect of regular heat training is how it changes muscle glycogen use. Muscle glycogen is essentially stored sugar your muscles can use to create energy. Regular heat training causes a glycogen sparing effect in the muscles. In this study, athletes used 40% to 50% less muscle glycogen during endurance exercise after they had spent 8 days doing heat acclimation training. This means their bodies were using less carbohydrate and more fat to fuel their efforts. 

Muscular Benefits of Heat Training

These are my favorite bits. Heat training offers some really awesome benefits for building and maintaining strength and muscle. Sauna supports and increases muscle hypertrophy. Heat shifts your body’s protein synthesis processes to less readily degrade existing muscle, and more readily grow new (or more accurately, larger) muscles. This is a great tool not only to combine with exercise but also for maintaining muscle if you can’t exercise. I recommend sauna work to anyone who is injured or rehabbing that wants to maintain their muscle

Then you have the effects on the endocrine system (your hormones.)

Sauna use typically increases noradrenaline slightly, prolactin, beta-endorphin and growth hormone. You probably already know what growth hormone does, since it’s use as a supplement is illegal both in and out of sanctioned sport, but the other hormones bring their own meal to the table. Prolactin promotes myelin growth, the sleeve around our neurons that lets us send signals throughout our body faster from the brain. This could have big implications for increasing the speed of skill learning, as well as reaction time. 

Beta-endorphin increases might explain another benefit of the sauna: feelings of peace, calm and happiness. I used to use the sauna nearly every day while training for the Crossfit games, and one of the biggest reasons had to do with floating on cloud 9 for hours after each session. 

Sauna is also well known to increase Brain Derived Neurotrophic Factor (BDNF) which I’m sure is good for your own brain health, but combines with the beta-endorphin increase mentioned earlier to have such powerful benefits on mood

Finally, for those of you seeking weight loss, Sauna work appears to have positive effects on weight loss through improving insulin function. This coincides with additional benefits for muscle mass, and strength. 

A Cautionary Tale (And How To Protect Yourself From Overdoing Heat Training)

What I essentially want you to take from this is that heat training is awesome for you, especially if you’re an athlete. We could rabbit hole about the studies for much longer than I’ve spent on them here, but the gist is that sauna work is powerful for endurance, great for your hormones, awesome for muscle, and benefits your neurology at the level of both mood and your physical brain and nervous system. 

That’s all great, now what. Should you start taking hotter showers? Running in the 100 degree Texas heat? 

What would you say if I suggested hopping in a dry sauna immediately after a heavy olympic weightlifting session? No pain no gain? Bring the heat? Well, that’s exactly what I did, and I went on to suffer a 3 hour panic attack that kicked off close to 3 years of chronic physical and mental health problems. 

I’d been training 2 hours a day, 5 days a week in high intensity interval training and olympic weightlifting as part of my desire to become a Crossfit games athlete. After reading Tim Ferriss’ Tools of Titans, I started incorporating regular sauna work. Mostly, this was great. I felt mentally challenged by the heat, but also relaxed and strong. 

I combined my sessions with deep meditations, and most of the time I left feeling like I sat at the calm stillness point at the center of the universe. 

Most of the time. 

On another occasion, I used the hot tub after a hard workout session. Like my sauna sessions, I meditated to ignore my discomfort, but when I got out, I felt dizzy and panicky. I sat down and let it pass, but later at work I got hit by an hour of strange hyper-alertness. Over the next week, I had 3 very strange episodes of this hyper-alertness which sometimes were accompanied by vertigo. 

Was heat the only factor? Not at all. I was using experimental nootropics, working till 2 in the morning, smoking 2 or 3 cigars a day and drinking coffee 24/7. 

But heat was the first true trigger. I never had any of these incidents until that hot tub incident, and though they went away when I took a break from caffeine and exercise, I kept using the sauna. 

A few months later I’d try a sauna session after a workout again, and that’s when my health crashed. 

I am not trying to scare you away from the heat. I was an extreme case by any measure, but my point is just this: Don’t be a hardhead about it. Heat is a powerful tool. It is powerful enough to make you superhuman. It is also powerful enough to hurt you. 

This is why I strongly recommend combining heat training with heart-rate variability measurements. 

Get an HRV monitoring device, like an OURA ring or a Whoop band. These devices monitor the recovery of your nervous system. Sauna use can cause your HRV scores to get lower without improving. This means you are not recovering well from the admittedly high stress of a sauna session. 

By using these devices, you can modify your sauna use to be less intense on days when you need more recovery, or to know when you should use additional tools. 

Electrolytes are often all you need to get your HRV back up after a sauna session, and I always keep stuff like Robb Wolf’s LMNT product on hand when doing heat training. 

For a guide to HRV, check out my article HRV: A Deep Dive Into The Most Important Metric for Health, Fitness, and Performance. For now though, just know that a device like an OURA or Whoop band will do the work for you. Increasing HRV means your recovery is good. Decreasing means bad. That’s the gist.

Getting Hot (How To Heat Train)

I dare not say heat training is easy, but it is simple. Like much of fitness, it’s tough and that’s a lot of why it’s good for you. Personally, I recommend sticking to a dry sauna 2 or 3 times a week, separate from workouts, if you don’t have an HRV monitoring device. 

I like to do 15 minute sessions inside the sauna with a 10 to 20 minute break in between sessions. I’ll do 3 sessions and then stop. Between sessions, I like to jump in a cold pool if I have access or at least use the gym’s showers. 

For this section, I’m gonna do things a little differently and offer bullet points I find useful for using heat training. 

  • Listen to Your Body

Regardless, I always listen to my body. Many times I use the sauna, I cut out a round or two, especially if I’m using the sauna at night and I’ve already worked out that day. There are many times I’ll get in the sauna for a single session and then go home. 

Of course, you can listen to your body. I used the sauna too often, but I also trained for 2 hours a day 5 days a week. It’s not all that surprising that I burned out my adrenals, but that’s the gamble I was taking. I knew my training load was excessive, but I wanted to see if I had the gonads to compete in the Crossfit games. 

That’s just me admitting, you might have a higher tolerance for sauna work. You might be fine going every day. You might be good with using a sauna immediately after a workout (though I’d say only do this after light cardio and never after HIIT or big weights.) However, I think all you really need are a couple sessions a week. Just like strength training and other forms of exercise, often our training load is not necessary for further benefit. It can be great for further skill practice, or just for mental health (the gym is a happy place for many.) 

  • Think of A Sauna Session Like A Workout

I like to think of the sauna as a workout of its own. Heat training has many effects that emulate a hard gym session, and it’s been useful for me to see it that way personally. I focus on recovering from sauna use just like I do with exercise. I get electrolytes quickly after a session, I try not to do too many sauna sessions and workouts in a single week, and I’ll take a break from heat training entirely every 5 or 6 weeks. As I’ve said earlier, I strongly recommend Robb Wolf’s LMNT Product. You might also include some magnesium. You can read all about that in this article.

  • Combine With Cold

When you are used to the cold, combining heat and cold training can be very effective. This is more intense for the body and may require more recovery, but I personally love this tactic. 

  • Use Your Environment

I love heat training using saunas but I also love just training outside during the summer. Right now in Dallas, we’re averaging 96 degree days with a “feels like” 105. As Jocko might say “stand by to get some!”

As summer comes around, I make a point to maintain all my outdoor exercise habits. Workouts are outdoors in the heat at 5pm. I hike 4 to 7 miles around midday, writing articles on my phone. And I try to wear as little clothing as possible while doing it for Vitamin D. 

It might sound intimidating, but you’d be surprised how much your body can handle when you give it a chance. I don’t recommend trying to go from only training in a gym to running 5ks in death valley overnight, but start walking a mile around your neighborhood in peak heat. I think Vitamin D is better than increased heat, but you can even try wearing sweats while you hike. 

This way you’re getting a lot of other great benefits, such as walking (Kelly wrote a whole article about this topic) and being an adaptable human being. 

Another part of using your environment is using your bathtub. Don’t have a sauna? Most of us can fill a bath with hot water. I actually find hot tubs and hot baths more intense than saunas in many scenarios. 

  • Get Fancy (With Infrared Saunas)

Infrared saunas are basically saunas that also send special light deep into your tissue that creates heat. Since that sounds like a bad superhero origin story, I’ll also mention that they are well shown to be safe and very good for your health. 

If you have some money to burn, or have access to a health club with an infrared sauna, I think these are the pinnacle of heat training. You can get some really awesome infrared saunas for your home, but most cities have them at health clubs. These locations will probably also offer great services like cryotherapy, or floatation therapy tanks (which I think are still one of the best meditation therapies out there.)


Alright. Let’s bring everything together. Like cold therapy, heat training activates a ton of biological responses in your body that are beneficial for your health and wellness. 

To name a very brief few, heat training improves endurance by increasing blood volume, improving glycogen efficiency, and other mechanisms. It is also especially powerful for building muscle. It causes hypertrophy, increases hormones like growth hormone and BDNF, and even improves mood with beta-endorphins. 

These are only the tip of the volcano. Heat training is being looked into for preventing cancer, improving mental health and function, and detoxification. 

When it comes to doing heat training, saunas are the number one tool. Most studies on the topic use saunas. Just remember, this stuff is taxing on your body. Let yourself recover and keep electrolytes on hand after sessions to lower the risk of nervous system fatigue. I strongly recommend monitoring your heart rate variability (HRV) alongside sauna use. 

I hope this material has proven valuable to you, and helps you discover the power of heat training and further improve your Ready State!

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