The Knowledge Behind My Sauna Article? It Actually Came From One Book

The day after I published my sauna article, a thought hit me.

“All that stuff I wrote about the right way to take a sauna, and how this ‘totonou’ (getting in the zone) thing works… where did I actually learn that?”

When I thought about it, there was only one answer.

It all came from a single book.

“The Doctor’s Guide to Sauna” (Isha ga Oshieru Sauna no Kyokasho) — subtitle: Why do business elites reset their brains and bodies with sauna?

The author is Dr. Yasutaka Kato. He’s a project assistant professor at Keio University School of Medicine and serves as the representative director of the Japan Sauna Society.

Among sauna fans, this book is treated almost like a bible. I read it about two years ago, and from that point on, my whole sauna experience completely changed.

And on this blog I’m writing now, “Pon’s Hobby Room,” most of what I can speak about “from real experience” is actually built on knowledge I got from books like this one.

I use AI like crazy, but even so, I genuinely believe that reading is, in the end, the strongest thing of all.

Today I want to write about why — and I’ll get a little serious about it.

🎯 The hard limit of information you get from AI

I use ChatGPT and Claude a ton on a daily basis.

At work and for running this blog, there’s a mountain of stuff I hand off to AI — research, summarizing, structuring, proofreading.

But the more I lean on AI, the more I’ve noticed something.

And that is — information I get from AI doesn’t stick in my head.

For example, if you ask ChatGPT “tell me how to take a sauna,” you’ll get a pretty solid answer back in 10 seconds. Super convenient, right?

But that info you got in 10 seconds — can you still recall it a week later?

I’ve finally started to understand why this happens.

• AI’s answers are a collection of “dots.” They never form a line
• Since you didn’t actively go get it yourself, your brain doesn’t flag it as “important”
• Because the answer comes instantly, there’s no process of thinking it through

In short, information that took no effort doesn’t take root.

📖 Why knowledge from reading actually stays in your head

On the flip side, knowledge I get from reading a book sticks around, oddly enough.

The contents of “The Doctor’s Guide to Sauna” are still in my head — enough that I can write a sauna article — even though I read it two years ago.

When I try to sort out why it stuck, it comes down to this.

① It’s been filtered through an author

Dr. Kato gathered the medical evidence and organized it into a coherent system.

That’s a totally different quality of organization than the fragmented bits AI scrapes together.

② It enters your head as context, connected by a line

The effects of sauna, how the brain works, how the autonomic nervous system functions — these are all tied together by a single line: “why does ‘totonou’ happen?”

It’s the feeling of remembering the whole context, not just the fact.

③ Because you read it slowly, it becomes your own words

It takes a few hours to a few days to finish one book. And the whole time, you read it while comparing it against your own experience.

So it sinks in to the level where you can “explain it to someone else in your own words.”

The reason I could write a sauna article on this blog is exactly that. I cross-checked what I read in the book against my own sauna experiences over and over, until I could write it in my own words.

If I’d only used AI, I can say for sure I’d never have gotten there.

🤖 How I split things between AI and reading

So does that mean AI is useless? Not at all.

In my head, I split them up roughly like this.

• 🤖 AI: streamlining work, instant research, organizing, summarizing, proofreading
• 📖 Reading: building the trunk of my thinking, updating my values, understanding things systematically

If I had to put it in one line: “Use AI to find answers, use books to deepen questions.”

For example, “tonight’s dinner recipe” — AI is plenty for that.

But something like “why do I even cook in my life?” — a book will take you way deeper.

This balance is what works for me right now.

⏱ My tricks for sticking with reading, even as a busy 30-something

“Okay, I get that reading is good, but I don’t have the time.”

I think that’s the real struggle. I work full-time on weekdays while running this blog, so trust me, I totally get it.

And yet I still manage to read 3 to 5 books a month. There are probably three reasons for that.

① Lock in a time slot

The 30 minutes before bed, and my commute on the train. I’ve decided those are my “reading slots” and I stick to them almost every day.

Doing a set thing at a set time is what keeps it going.

② Don’t get hung up on paper books

Paper, e-book, audiobook — once I accepted that any of them is fine, it got so much easier.

Pick based on the situation. Paper before bed, audio during the commute, that kind of thing.

③ Don’t obsess over finishing

If a book isn’t for me, I drop it partway through.

That rule of “I can’t move on until I finish a book” is one you’re better off ditching.

Life is too short to spend time on a boring book.

🎧 Listening while doing other stuff is the cheat code | Audible as an option

And the thing I’ve been most hooked on this past year is Audible (audiobooks).

Commuting, working out, doing chores, walking home from the sauna — there’s actually a ton of time where “your hands and eyes are busy, but your ears are free,” right?

Being able to convert that time into reading time is Audible’s overwhelming strength.

It’s 1,500 yen a month for unlimited listening to eligible titles, so if you listen to 3+ books a month, you’re already coming out ahead.

And the best part —

“The Doctor’s Guide to Sauna” is available on Audible.

Walking home from the sauna, listening to this book with a freshly reset head. That’s honestly the best experience.

The mechanics of sauna link up with what your own body just felt, and your understanding deepens fast.

You can listen to one book during the free trial and cancel — totally fine. You can try it with zero risk.

📝 Wrap-up | Streamline with AI, go deep with reading

Let me wrap things up.

• 🤖 Use AI for everyday efficiency (research, summarizing, organizing)
• 📖 Use reading to build the trunk of your thinking (systematic understanding, values)
• 🎧 If you can’t carve out time to read, listen while you do other things with Audible

This balance is just right for me these days.

My sauna article, too, traces back to what I learned from a single book.

Try opening up a book today. And if that feels like too much, starting with your ears through Audible is totally a valid move too.

Pon