I still haven't tried any of the breathing techniques, but the book published on Wim Hof's method[1] is a fascinating read.

It was written by an investigative journalist that was initially skeptic of the method, and decided to debunk the myth.

[1] What Doesn't Kill Us: How Freezing Water, Extreme Altitude, and Environmental Conditioning Will Renew Our Lost Evolutionary Strength

https://www.amazon.com/What-Doesnt-Kill-Environmental-Condit...

For anyone interested in the topic, I strongly recommend reading "What Doesn't Kill Us" [1], by Scott Carney. Scott is an investigative journalist who initially planned to debunk Wim Hof's [2] (aka the Iceman) methods, and ended becoming one of Wim's biggest followers, and publishing a NYT best-selling book telling his journey.

It's a fascinating story, and covers a lot of the science behind breathing techniques, how our autoimmune system works, and step-by-step process to take advantage yourself.

ps: if you want a TL;DR, here's an interview [3] with Scott that summarizes the book well.

[1] https://www.amazon.com/What-Doesnt-Kill-Environmental-Condit...

[2] https://en.wikipedia.org/wiki/Wim_Hof

[3] https://www.dragondoor.com/interview_with_scott_carney_autho...

"Why We Sleep", by Matthew Walker [1]. I've read a lot about sleep over the years, but I still found it fascinating and comprehensive.

I've mentioned the book on several other threads [2], so I'll avoid repeating here.

Along the same lines of expanding the ability of your body/mind, one that I'm currently reading is "What doesn't kill us" [3]. Pretty fascinating to think that we have a lot more control over our immune system than originally thought.

[1] https://www.amazon.com/Why-We-Sleep-Unlocking-Dreams/dp/1501...

[2] https://news.ycombinator.com/item?id=17606274

[3] https://www.amazon.com/What-Doesnt-Kill-Environmental-Condit...