4 ms·

I'm pretty new to it, so my rounds are only just above 1 minute. I might just not have the CO2 tolerance yet, but I definitely notice some cognitive effects. My

I'm pretty new to it, so my rounds are only just above 1 minute. I might just not have the CO2 tolerance yet, but I definitely notice some cognitive effects. My blood oxygen saturation during these generally stays above 90%. I'll try pay more attention to when the issues kick in and measure my blood oxygen then. I've read that it's around 50% saturation that you're in danger of passing out, and most oximeters are only accurate to 70%. I've gotten no where close to those numbers though, so it's likely just lack of CO2 tolerance.

curun1r 9y ago
I wouldn't worry about O2 saturation with regard to passing out. When I've done holds using an oximeter, I can't really get my SpO2 below 90% either, even when I know I'm pretty close. But there's just so much that contributes to being near blackout that isn't oxygen saturation that you're better off learning to recognize the subtle physiological cues. For example, you can blackout earlier (higher measurable O2 saturation) if you inhale too deeply. It may seem counterintuitive, but expanding your lungs more fully can increase pressure on the heart and make it harder for it to distribute the blood to your body and brain. Your blackout O2 saturation will also differ depending on how much gravity your heart is having to deal with. Standing, sitting and lying down will have different blackout O2 saturations and that's only considering dry training...in water, both swimming position and depth/pressure will factor in too. So when I'm doing a hold, the main things I pay attention to are first diaphragm (first contractions, for me, are pretty reliably at 1/3-1/2 of a max hold), and then the feeling in my fingers/toes, but you'll start to notice a couple of other sensations as well if you start pushing yourself to the brink. Incidentally, you can be pretty sure if CO2 tolerance is your limiting factor if your first contractions come in the second half of your hold.

curun1r 9y ago

I wouldn't worry about O2 saturation with regard to passing out. When I've done holds using an oximeter, I can't really get my SpO2 below 90% either, even when I know I'm pretty close. But there's just so much that contributes to being near blackout that isn't oxygen saturation that you're better off learning to recognize the subtle physiological cues. For example, you can blackout earlier (higher measurable O2 saturation) if you inhale too deeply. It may seem counterintuitive, but expanding your lungs more fully can increase pressure on the heart and make it harder for it to distribute the blood to your body and brain. Your blackout O2 saturation will also differ depending on how much gravity your heart is having to deal with. Standing, sitting and lying down will have different blackout O2 saturations and that's only considering dry training...in water, both swimming position and depth/pressure will factor in too. So when I'm doing a hold, the main things I pay attention to are first diaphragm (first contractions, for me, are pretty reliably at 1/3-1/2 of a max hold), and then the feeling in my fingers/toes, but you'll start to notice a couple of other sensations as well if you start pushing yourself to the brink. Incidentally, you can be pretty sure if CO2 tolerance is your limiting factor if your first contractions come in the second half of your hold.