[RoosterRedux]

What's been your wife's experience?

I've read some articles and watched some videos on CO2 tolerance being important for increasing fitness (related to the more efficient movement of oxygen to muscles IIRC). It seems counterintuitive, but that doesn't mean it doesn't work.

[ConservativeMind]

She seldom used it, but, instead, does sprints for 30+ seconds at a time, every few days, which leave her panting.

CO2, which we exhale, dilates our blood vessels. You can lower your blood pressure, temporarily, by exhaling and not breathing back in for a few seconds.

Strangely, a keto diet generates less CO2 in our bodies, which would work to negate this effect:

https://www.dietdoctor.com/can-keto-improve-copd-or-are-we-getting-a-little-too-excited-about-possible-benefits