It makes me have to state these things over and over. I am talking about good athletes, just like you are talking about good 'internal' people.
I think one of the major points of contention comes from your attempt to take descriptions from the IP language and applying them directly to what athletes are doing... or at the very least, taking people's descriptions of IP movements and simply saying "Athletes do that too!"
Perhaps it might be helpful to attack it from a different direction -- that is: establish a baseline definition on what you think good athletes are doing using your own words, preferably using fairly neutral and mechanical terms.
From there, we might be able to do a reverse mapping of what good IP people do using more neutral terms as well (or we might not), and see if they match up.
To get the ball rolling, something along the lines of... "Describe how a good athlete would setup their body to resist a push of 5 lbs, 25lbs 100 lbs, 200 lbs... and so on."