Rule of thirds, Total Oxygen in body during breath hold underwater swimming

[Conan777]

I have heard about the rule of thirds for free-diving http://freediveuk.com/the-freediving-breath-hold-rule-of-thirds/. Assuming that I don't hyperventilate before breath hold underwater swimming and I start getting a tiny burning urge to breathe on my chest at 1 minute, would I black out after 3 minutes of being underwater? If I could get through stages one and two in the rule of thirds, would I get to the third stage when I hit 2 minutes? Assuming I resist the urge to breathe on my chest with all my might and keep on holding my breath underwater, would I have little oxygen in my whoe body, in the blood, lungs, and spleen at minute 3, since little oxygen to the brain can cause unconsciousness?

 

[Acidjack]

Sounds interesting. Could possibly be accurate. Some suggestions from an advanced freediver?

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[Jaap]

I would be careful with these kinds of 'rules of thumb'. Some days I get contractions after 3:30, sometimes after 1:30. My total breath hold does not differ that much. Some people don't feel contractions at all. I wrote an article on shallow water blackout a while ago: http://freedivewire.com/minimizing-freediving-risk-shallow-water-blackout/ you may find some useful info there. The bottom line is that you cannot know your oxygen saturation while you're diving, and even if you did know it will change upon going to the surface because of the partial pressure change. Hence, you never truly know how close you are to blackout. However, lots of diving and practice on the line does help to create some awareness of your own limits.

 

[Acidjack]

When you get contractions after 3:30, how much more time can you stay under water?
And whats when they kick in after 1:30?
Is the total apnea time approximately the same?

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[Jaap]

This is from statics. I don't trust the onset of contractions underwater as an indicator of how much I have left, and it would depend on what kind of suit I am wearing, how deep I am diving, what kind of a warmup I've had etc. Total apnea time for these specific statics is approximately 4:30 - 5:00.

 

[Acidjack]

Ok, ty. Good to know.

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