re: Blood decreases greatly after doing some breathing exercises

Breath work is and has been a common practice for a very long time. Recent studies have shown that certain breathing patterns stimulate the Vagus Nerve which in turn causes an uptick in your Parasympathetic Nervous System (part of your Autonomic Nervous System that regulates rest, digestion, recovery, and healing).

There are more ways to stimulate the Vagus Nerve during breathwork. A few of these are, breathing in and out through your nose only. Also, having a breathing cadence that makes your exhalation twice as long as your inhalation is very effective. An example would be to breath in for 4 seconds, hold for 4 seconds, and breath out for 8 seconds.