Your confident ignorance motivated me to at least dig up some cursory research on this space, I hadn’t previously bothered because I live and breathe this stuff (pun not intended).

As a young impressionable, I set out to understand and overcome performance anxiety as someone who suffered from it. After some reading, one of my conclusions was that I should do the most stressful thing possible to understand stress better and develop physical tolerance to stress. This culminated in me signing up for a series of Muay Thai interclub fights because getting punched (or kicked) in the head while pushing your heart rate to ~200bpm is definitely up there for “stressful circumstances”.

Turns out breathing really helps in that situation too beyond just taking in more oxygen - relaxation is critical for both technical execution and strategic thinking.

Slow breathing also really helps with freediving - another hobby of mine that I dabble with that happens to involve going deep (no pun intended) on conscious relaxation.

But sure, it’s just you taking in oxygen to moderate your heart rate. Here are some papers I surfaced for you and others who are interested

[0] https://www.science.org/doi/10.1126/science.aan1466

[1] https://www.science.org/doi/10.1126/science.aai7984

[2] https://www.frontiersin.org/journals/human-neuroscience/arti...

Note that fast breathing doesn’t necessarily mean high oxygen uptake. Deep breaths result in higher oxygen uptake (since you spend less time just moving the same stale air up and down your airways), and deep breaths are usually easier to perform when breathing slowly.