[nikitoci]

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.

[timewizard]

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.

[OxO4]

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.

[FrojoS]

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

[FrustratedMonky]

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?

[aqme28]

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.

[Azrael3000]

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.