OK, so I entered, I entangled and I wrenched. Easiest way to prevent his arm from being wrenched hard is by sinking the elbow.
So normally at this stage I would change to another technique and the push hands game goes on.
But no. I decided I will have a little fun, apply a little leverage.
Sinked? Sure? OK.
Light pressure. My student magically lifted his arm up and I can wrench his arm all over again.
So why did he so easily give up his bent and sunk elbow and allowed his arm to be straightened again?
Such puzzles are what we study when we play the push hands game.
Its nothing to do with chi though I could use that as a reason to make it seem magical. Basically, its nothing but a simple application of leverage; a topic which I had touched on in TaijiKinesis Vol 2.