There is one thing I want to emphasize. Athletic events and deadly encounters aren't the same thing. A boxer or MMA fighter fights 3 minute rounds in a ring or cage, with short breaks. Wrestlers have their wrestling periods. But most deadly force encounters are over in a *very* short period of time. With that in mind, oxygen transport to tissue is completely irrelevant. In all but a small fraction of deadly force encounters, we are *NOT* engaging our aerobic metabolism. That metabolic system is incapable of generating maximum force. If you want to run cross country or a marathon, train your aerobic system to the max. If you want to run 100 meters or survive the bad guy, you must master the phosphocreatine and glycolitic energy pathways. That's were all the peak force energy resides.
This is an excellent point most people miss Bill , So many people think fitness is the key to controlling heart rate and duration , which is true in a controlled context .
however fact is the fitter and stronger you are the more potential you have , you will under the cocktail dump all that potential as quickly as a non athlete , you will exert more and hit your threshold heart rate etc just as quickly as the non athlete.
Breathing is the only control you have over this .
I did a lot of experimentation while doing high intensity tabata intervals , with measuring heart rate and recovery , and the degradation on performance , the recovery mechanism is breathing , and you can measurably change your heart rate with different methods, however it is a recovery the work is the work and will have the effect , I believe under duress you will spike , the only thing you can truly do is be prepared and experienced in the pre contact breathing methods , and the post contact breathing methods , and be familiar how it feels to function under an elevated state .
this stuff is very measurable , do it smart , create some conditions , get the required medical checks and advice and have at it .
after doing it the huff and puff debates become pretty academic , its kind of missing the forest for the trees , its reeks of controlling your heart rate breathing for performing kata , or sparring , or doing class for 90 minutes .... not the stimulus were debating . Its more like a breathing while running discussion vs a life and death struggle.
Its a big topic , and everything said seems to be arguable and counter arguable , and we all end up painting different pieces of the elephant .
But the way to understand IMHO is experience and experimentation, not in trying to control it , but to understand it and whats needed to optimise function within it.
The thing to keep in mind is that we need to learn to match any breathing intensity pattern to the intensity of our physical motions/demands.