Re: What is "IP" discussion of Internal power.
My own view is that the structure of person A is being modified at the time of contact by person B so that A is unable to push in a horizontal direction towards person B. At this point person B feels there is no force being received and person A can be 'confused' about why they can't push. The base of person A (weak) and B(strong) at times reveal much, though with sufficient understanding they become ess relevant and you see in the video examples of that
As a somewhat mechanistic person i can see that using external structure and 'tricks' help to get the point across about where the forces go (via topple vector and understanding the base), but it also highlights for me the fundamental importance of internal structure (as the connecting point between infinite power of the ground and contact points). Then that everything can be made much smaller/ invisible where i think the science points the way to IP but maybe not how to get there if that makes sense.
*cringes slightly* but is hopeful.....