I keep seeing chi talked about like it explains everything and nothing, which is usually where I start getting suspicious. Breathing, structure, balance, attention, all useful. But if the method falls apart the second the other person resists, then I do not care how elegant the explanation sounds.
So I am asking the people who actually train this stuff, not the armchair mystics: what changes under pressure, and what does not. If you have a drill that shows the difference, I want that more than another speech about energy.