They probably super saturated with oxygen using deep breathing techniques prior to this contest.
That subjects you to what is known as shallow water blackout which comes on suddenly with no warning.
I used to do the same thing when I was young and ignorant.
I was amazed, though, at how long I could hold my breath.
That’s interesting information. I used to swim in high school and we did deep breathing. I would try to see how many lengths of the pool I could swim underwater without a breath. I always got myself into a somewhat sleepy state doing the deep breathing but as you said, I could stay under for a long time. I didn’t realize I was putting myself in such a dangerous state.
Thanks for posting that. I have done the same and never knew about this. I thought I was supersaturating the blood with oxygen.
After your post and some quick searching, I learned that there is little difference in the O2 level, only the CO2 level is depressed, which is what triggers the urge to breath.
People hyperventlate, reduce the CO2 levels, run out of O2, pass out without feeling the urge to breath.
http://www.scuba-doc.com/latenthypoxia.html
I don’t think you can supersaturate the blood with oxygen unless it’s pressurized (hyperbaric) or you’re breathing a percentage higher than room air (which is only 21% oxygen). The hyperventilation would reduce CO2, which is actually your drive to breathe. With reduced CO2, one wouldn’t have the necessary chemical trigger of receptors in the brain to initiate a breath.
Maybe I’m wrong but I’m only basing this on what I’ve learned in nursing school.
I used to practice breathholding after hyperventilation
Records:
swam 3 lengths of swimming pool underwater
Held breath once for 4'45”
I don't recommend it to others, but
it did, powerfully, teach self control
What it does is strip the CO2 from the blood stream
Most breathing efforts are driven by
raising CO2, not lowering O2
Drastically dropping CO2 levels can cause
the breathing reflexes to simply "forget" to breath