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The Truth About Saunas

Humans have used the heat to thrive for 1.8 million years. Here's how that can guide us today.

The Truth About Saunas
A run last weekend on one of my favorite (and hottest) trails.

Post summary

  • On Monday, we learned about some health and fitness benefits of the heat.
  • The research around heat exposure therapy is interesting ...
  • ... but using a sauna can feel like one more thing on a laundry list of health practices we should all be "doing."
  • This post will explore how I think about heat exposure from an evolutionary perspective, my thoughts on saunas, and how I use heat exposure in my life.
  • You'll walk away with a practical and powerful perspective on leveraging the power of the heat.


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The post

On Monday, we covered some benefits of heat exposure.

To understand the topic, I spoke with Chris Minson, PhD. He's a researcher at the University of Oregon and arguably the world's leading mind on the health and fitness benefits of heat.

The health benefits of sauna use are particularly compelling. For example, one study found that people who used the sauna at least four times a week were 40 percent less likely to die of heart disease.

I think this stuff is fascinating. But, a moment of honesty: am I actually getting in a sauna? That's another story.

There's so much we can do to improve our health. When I think about health practices, I defer to those that:

  • I enjoy. If you hate it, you won't do it.
  • Are practical. The easier it is to do and the more places you can do it the better.
  • Are efficient. Think larger impact in less time.

With that in mind, I do have something of a "heat exposure practice" that allows me to leverage the power of the heat.

But to understand why it works and how I use it, we need to understand how humans used the heat to their advantage for millions of years.

Humans in the heat: a brief history

  • Section summary: Humans evolved to thrive in the heat. Other mammals don't.

If you hate exercising when it's hot out, let me tell you—you're living in something of a comfort crisis.

Humans would have all died off had your ancestors not been willing to exercise long and hard on the hottest days.

You can almost think of humans as the lizards of the mammal world.

Compared to most other mammals, we're not strong, powerful, fast, or agile. But we're really good at managing heat. Especially when we're moving.

For example, on a hot day a relatively fit human will beat most other mammals in a long-distance race. Lions, tigers, bears, dogs, etc. Other mammals can't cool themselves efficiently, but we can.

We used this weird skill to survive.

Our ability to manage heat started with foraging. We'd walk around looking for food at the hottest point of the day when predators were resting. This allowed us to find food and not get mauled.

Over time, evolution did its thing. Our bodies began to change in ways that made us excel in the heat.

For example, we began losing most of the hair on our bodies and developing sweat glands. Our sweat and lack of hair let us stay cool as we moved across the earth.

Eventually, we began moving even faster. We started doing what’s called persistence hunting: slowly but surely tracking and jogging down prey for miles upon miles.

Because our prey couldn't cool itself like we could, it would eventually topple over from heat exhaustion. Then we’d kill it, carry it back to camp (carrying is another skill we're uniquely good at), and have it for dinner.

Duke researchers note that early humans likely gathered food and performed our persistence hunts in the middle of the day when the temperatures were hottest.

This was the most uncomfortable time to gather and hunt food—but it allowed us to capitalize on our ability to endure in the heat.

The researchers found that modern persistence hunters in the Kalahari desert can run for 5 hours and 40 minutes in the heat without it impacting their abilities. The Kalahari averages about 100 degrees during its hottest month.

We're all likely still capable of this today. But it's been trained out of us by the modern world.

We live at 72 degrees. In the peak of summer, exercisers retreat into air-conditioned gyms. Our temperature-controlled world has changed us.

We've lost a free, powerful stimulus that made us human and can still improve our health today.

How I leverage the power of the heat

  • Section summary: We cover a practical and powerful perspective on heat exposure (what I think of saunas, heat exposure, and how I use them), plus four laws I follow for exercising in the heat.