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Comment by timewizard | Hacker News Reader

If I need to hold my breath underwater for a longer period of time I'll hyperventilate on the surface just a little before diving. In my experience your lungs don't "burn" as quickly and so you can dive a little longer.

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It’s dangerous, since hyperventilating removes co2 from your blood, and raised co2 level is primary trigger for the urge to breathe reflex. It may feel better to hyperventilate and dive longer but you’re risking suddenly blacking out. I’m a free diver and this is one of the first things you are trained not to do, as well as never to dive alone, for safety reasons.

Ah the wisdom has changed. This was more often taught when I was younger, which yes, was quite a while ago. The warnings given then were don't go for depth with this method, exhale occasionally while underwater, and manage your breath again immediately on the surface.

Interesting. Got a good source? I should definitely look into this again.

The people around the pool and lake where I grew up? From what I'm reading while searching it seems that "hyperventilate" is probably a bad term for the type of breathing I was shown. We wouldn't do it until we felt a conscious change like dizziness but more like 4 to 8 good deep full and fast breaths before holding, enough to notice, but not so much that it presented the dangers I'm now reading about.

That is still considered hyperventilation as a freediver, even though you might not feel any symptoms. The suggestions you gave in your previous post are dangerous and should not be done. Please take a proper course to learn about free diving physiology and safety. Otherwise this sport can get dangerous very quickly.

Any freediving course. You have to breathe normally for an extended time, then dive, then take an extended break, hyperventilation just makes it easier for you to get yourself killed.

https://www.divessi.com/en/get-certified/freediving https://www.padi.com/education/freediving https://www.freedivinginstructors.com/ https://www.aidainternational.org/Education/AIDAFreedivingCo...

I've only taken the SSI training but I guarantee none of the different freediving organizations will recommend the type of breathing you are discussing, and in fact a large part of the intro course hammers home that you don't breathe that way.

Freedivers are also taught not to exhale underwater, because it wastes oxygen and lowers your CO2 level, making it harder to know when you actually have to come back up. Your body can't sense the level of oxygen it has, so freedivers rely on CO2 levels as a proxy, so messing with it is dangerous.

And you also becoming much less buoyant and will not surface without actively swimming or pulling the line.

So just curious. You do want to have the CO2 levels, so you get the trigger to breath? But to free dive don't you want to stay down longer? So is the method more about dealing with the urges? Mental ways to understand the urge to breath, but be able to block it?

There are two gases that need to be exchanged when you breathe. You need to get rid of CO2 and you need to get O2. When you hyperventilate, you purge CO2, but don't really change your O2 content.

This matters only because CO2 is what triggers your desire to breathe, but O2 is what causes you to actually pass out or not. So what happens is that you might pass out before you realize you need to come up for air.

Correct. You can deal with the urge to breathe with your brain. High co2 has additional benefits for your metabolism, you just need to deal with it. If that sounds interesting take a free diving course its a great way to learn more about this fascinating sport.

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