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Ice bath safety and hypoxic blackout

 •  • by Paul Ingraham
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Is it dangerous to dip yourself in very cold water for therapeutic purposes? Probably not as dangerous as many other popular activities! Including a bunch of other water-related ones (drowning is the 3rd most common type of injury death).

But there is a medical consensus that the ice bath danger is real. Although younger and fitter people are much less likely to have trouble, the popularity of the practice has led to large numbers of more vulnerable people giving it a try — especially people who are actually struggling with their health. These are literally motivated by their vulnerability! (Not the only place we see this pattern.)

The risks include hypothermia, shock, heart attack, and stroke (see Tipton). However, documentation of injuries and deaths by these causes during full body cryotherapy is minimal — either because it’s quite rare, or under-reported (always likely), or a bit of both.

Photo of a winter landscape. In the foreground, a woman’s legs and an icy lake: one foot is on the snow, and the other is stepping into an extremely icy pond or stream.

There have been quite a few documented deaths related to “hypoxic blackout,” AKA “shallow water blackout.” This sinister phenomenon, well known to free divers, occurs when hyperventilation is combined with water and breath holding. Significant hyperventilation temporarily suppresses the reflex to breathe, creating the illusion that you can hold your breath for longer than you actually can. You feel like you can keep going when you cannot, which leads to (unpredictable) blackouts while in the water.

But who’s hyperventilating and swimming or breath holding in the water? Who would do such a thing? Other than free divers?

🙋🏻‍♂️ Uh, I have. Quite a bit of it, actually.

It’s more common than you might think, primarily because of the popularity of the Wim Hof Method, which includes both hyperventilatory breathing exercises and immersion. While taking this risk is officially discouraged by the WHM, abuses and careless malpractice may be common (that’s a substantive video on this topic, worthwhile if you’re interested).

To minimize your cryotherapy risks:

  1. Do not take up cold bathing — or do it more conservatively — if you have significant health issues, especially cardiovascular pathology.
  2. Go feet first, and keep breathing steadily.
  3. Allow time for re-warming, and don’t do dangerous things like driving until you have fully recovered.
  4. Important! Never hyperventilate before swimming or breath holding in water. Just don’t do it.

This post is an excerpt from a whole new article dedicated to systemic cryotherapy, which I wrote in the aftermath of writing about a test of the Wim Hoff Method last fall:

Members-Only Addendum: I flirted with hypoxic blackout for years … without knowing it

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For many years I practiced what I thought of as a “sinking meditation” — and it was much more dangerous than I realized. I think it feels neat to sink to the bottom of the pool and meditate while holding my breath. Yes, I really did a lot of this — as I have confessed before, I used to be a flake, always keen to try things like meditation. But I’m a busy guy and I don’t like *long* meditations, so just a minute or two drifting breathless, at the bottom of a pool? •chef’s kiss•

Pool bottoms are peaceful places, and slowly sinking is a strong sensory metaphor for descent into an altered state. I always thought it was very pleasant.

During my massage therapy career, I had a client who was an elite free diver; she regularly held her breath for about 6–7 minutes, and hung out with a free-diving crowd that was generally getting to 8. That’s still well short of what’s possible, but it still blows my mind. Almost unbelievably, as of 2023, the world record for breath-holding was 24 minutes and 37 seconds. Astonishing.

I am fascinated by breath holding. I can easily last a minute, but my personal record is trivial: I got to two whole minutes once. And how did I get there? By hyperventilating!

As I know now, hyperventilation is a Very Bad Way to improve your submerged breath-hold duration, because of the risk of hypoxic blackout. Entirely oblivious to the danger, I did this semi-regularly for years! I was especially dangerous because I was often deliberately pushing the envelope, seeking out my limits. And even worse: I was often alone, in a private pool, where there would have been no hope of being noticed in time if I had passed out.

I shudder to think how close I probably came to an ignominious ending. In retrospect, that may well have been the most dangerous thing I’ve ever done.

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