Mark Divine appears on episode 123 of BarbellShrugged. He introduces BoxBreathing. It sounds straightforward but its importance is highlighted in the video.
BoxBreathing: “a breathing method where we essentiall breathe through our nose into our abdomen and what we’ll do is breathe in a box pattern.” Mark Divine
You inhale and hold to a certain count and exhale all the way to the same count. If you don’t practice breathing then you don’t do it very well. This activity helps you to relearn breathing through your nose and be able to maintain that as the thresholds start to climb.
Breathing through the mouth upsets the balance of oxygen and carbon dioxide. This can lead to a bit of toxicity which further degrades your performance.
Little known fact. When you breath through your nose it generates a trace element of nitrus oxide which helps deliver the oxygen to your cells. This boosts your performance. Also there are nerve bundles behind your solar plexes. As you breath through your nose into your belly it stimulates the parasympathetic nervous system, which calms you down. NONE of this occurs when you breathe through your mouth. Breathing through your mouth goes directly to your upper chest.
Furthermore the Act of focusing on that breath helps you to concentrate.
So if you want to see some immediate benefits in your performance you need to practice your breathing because Mark Divine says so.