Slow breathing (in yoga: pranayama) instantly down-regulates your nervous system by boosting vagal tone and lowering sympathetic "fight-or-flight" activity. When your breath lengthens, it signals your brain that you are completely safe, dropping your heart rate and lowering blood pressure.
I first learned about this in the army, called "tactical breathing". I still consistently use this before public speaking or if I feel myself in a manic/stressed state of mind.
It doesn’t signal anything. Your heart rate drops because you’re inhaling less oxygen so your heart is like “we don’t need this high fi flow” and slows down blood flow to lower energy expenditure.
Lower energy state always wins unless chasing energy source.
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...
Cancel the Muai Thai, switch to Judo immediately.
Your brain is attached to your inner skull with candyfloss like tendrils. They do not repair. Software engineering, even prompting, with a concussion or CTE is impossible.
Judo isn't that healthy either. Many Judo-ka have hurt their backs from the damage accumulated from falls and there are other ways to injure yourself in Judo. If you're looking for those sorts of high stress combat situations you can get that with Karate styles that practice a lot less contact. There's still high pressure but a lot less than full contact fighting where you're just hitting and getting hit all the time. Some chance of injury but it's a lot rarer.
I do agree that getting constantly hit in the head is probably not a good idea (e.g. boxing). If you want the stress of public speaking join Toastmasters or something ;)
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.