This is out of my area - I will gladly take your word for it.The strength and capacity of the diaphragm and other respiratory muscles speaks to their ability to both buffer acids from other muscles (and as the result of stress hormones) and use lactate for fuel, as these are highly oxidative tissues.
Professor Buteyko, who died about 20 years ago, would be the person to ask, but I think I can give his answer, which would be "because it works." As with many things Russian, finding what works is more important than understanding why it works. The professor had tremendous success in reverting the symptoms of many chronic conditions. As I understand it, the "aha" moment came in an emergency room when, looking across the room, he saw someone he thought was having an asthma attack who turned out to be having a heart-related chest pains.Why are you trying to raise your blood CO2, in the case of health and not exercise performance?
Chronic, low-level hyperventilation causes a myriad of health problems; fixing it the Professor's way involves keeping your blood CO2 high, which is done by breathing less - which is why I don't do any breathing practices that involve taking in a lot of air.
We test people as follows:
Sit up straight in a chair.
Take a few normal, relaxed breaths
At the end of a normal exhale (lungs are mostly emptied but not actively purged), close your mouth and pinch your nose shut with your fingers. We run a timer and ask you to release when you feel "air hunger." It is very important that you not artificially inflate your number by holding past the point of air hunger - no "I'm a tough mudder." It's a relaxed test, and when you feel air hunger, you stop.
The average test value is 15 seconds.
We then teach our students how to improve this number, which we call the Control Pause or CP. Our baseline, roughly comparable to someone getting all 2's on their FMS, is 25 seconds. Our goal, roughly comparable to someone doing their 1/2 bw press, is 60 seconds. Someone with a 60 second CP will need to take in much, much less air than someone with typical, untrained value - on the order of 1/4 the amount of air.
I am a lifelong, well-documented asthmatic - missed lots of school as a child, turned blue in the face coughing every time I got a cold, and took asthma medicines for decades as an adult. I no longer take any of those medicines, my allergy symptoms are 100% gone, I have lost my taste for sweets, and the list could go on and on - I am very, very, very much healthier as a result of my breathing practice.
Breathing through a straw will have somewhat the same effect - you'll get less fresh air, and your blood CO2 level will rise. The description of the "unreal calm" that it helps develop is spot on - higher blood CO2 has the effect of relaxing the muscles; the advice to remember what it feels like as you recover between swing sets is also spot on. Something very much like straw breathing is part of our practice and therefore something I do every day.
Last but not least, all this is, to quote Rif, "simple but not easy." It requires four 30-minute sessions per day for the first month, and most people need two 15-20 minute sessions every day to maintain. Improving is also often unpleasant - the body detoxes as your CP goes up - I speak from personal experience.
I am not convinced that we need to nasal breathe, beyond its use as a beginner's training drill (like breathing through the straws). Once you have control of your respiratory muscles, the only benefit to nasal breathing is the filtering of the air that passes through it, rather than the mouth. But I have no strong opinion on this. Your thoughts?
I don't know why, but it makes a big difference. Part of our practice is that some people actually tape their mouths at night to make sure they are breathing only through their nose. It's important, even very important.
One more thing - Professor Buteyko reported a 90% success rate; the other 10% didn't follow the instructions.
-S-