Nothing inherently dangerous about practicing breath holds at home, as long as it's done sitting in a bed or so in case of dizziness. Unless you hyperventilate (don't!) the pain will be too great for most people to hold until they black out. And one can always just start breathing before that, never beat your own PR by more than a few seconds at a time.
Of course, when setting records it's done in the water (because of the diving reflex), which should never be attempted alone.
I recommend apps for "co2 tables" when practicing.
Josh Waitzkin, chess prodigy, learning guru, almost killed himself by accident through breath holding work[0]:
"Josh Waitzkin: The 30-second version is that I was doing some Wim Hof-inspired breath hold work. I made the mistake of doing it during lots of reps of underwater swims, 50-meter swims, at a pool in New York City. And on my eighth or 10th rep, I blacked out in a bliss state and I spent four minutes in the bottom of the pool after blacking out from oxygen deprivation. This old guy pulled me out and, which I’m eternally grateful for, and I basically drowned. All the doctors said after 45 to 60 seconds I should have been brain dead or dead, but it was four minutes on the bottom of the pool and that my training saved me. Also, you could say, put me there—but that’s a whole other conversation!"
This phenomenon is well-known, probably more so than Wim Hof. You’d think a ‘learning guru’ would learn about the potential risks of holding ones breath underwater while hyperventilating before attempting it!
Hyperventilation passing out mechanism, for those interested:
Although the body requires oxygen for metabolism, low oxygen levels normally do not stimulate breathing. Rather, breathing is stimulated by higher carbon dioxide levels. As a result, breathing low-pressure air or a gas mixture with no oxygen at all (such as pure nitrogen) can lead to loss of consciousness without ever experiencing air hunger. This is especially perilous for high-altitude fighter pilots. It is also why flight attendants instruct passengers, in case of loss of cabin pressure, to apply the oxygen mask to themselves first before helping others; otherwise, one risks losing consciousness.[143]
The respiratory centers try to maintain an arterial CO
2 pressure of 40 mm Hg. With intentional hyperventilation, the CO
2 content of arterial blood may be lowered to 10–20 mm Hg (the oxygen content of the blood is little affected), and the respiratory drive is diminished. This is why one can hold one's breath longer after hyperventilating than without hyperventilating. This carries the risk that unconsciousness may result before the need to breathe becomes overwhelming, which is why hyperventilation is particularly dangerous before free diving.
Yes, because he did it while swimming. Parent is talking about sitting on your bed.
Obviously, when you combine such exercise with activities that require full attention, like swimming, frying a steak or driving a car you add a dimension of serious danger.
Wim Hof's breathing exercise is not designed for underwater dives, and he always urges people to do it somewhere safe, like in bed or lying on the ground. Maximizing breath hold time isn't really the point of the exercise.
I played it for a few weeks, and (at least where I played) it looks like when you are at a pond with fish and somebody throws in bread, except with humans instead of fish.
It's a good day when I learn about something so weird and wonderful. I'm from Canada, where the first world championship was held in 1980, yet I was completely unaware this sport existed.
My favourite facts from the Wikipedia page are: it is originally called octopush and was played with an uncoated lead puck.
Of course, when setting records it's done in the water (because of the diving reflex), which should never be attempted alone.
I recommend apps for "co2 tables" when practicing.