First define what the 'posterior chain' is. It's usually used to describe the posterior muscles (hamstrings, glutes, back etc.). How on earth do you move without 'activating' (a word people use that doesn't really mean anything) those muscles? It's not really a 'chain' either, those muscles don't work together at the same angles or anything. If someone uses words such as 'activate' or 'posterior chain' that's another clue that the person really has no idea what they're talking about. Take notes kids.
Exactly movement is the clue, with the heel on the floor, there isnt movement, only up.Heel is the biomechanical break, for any other movement. When lifted, what lifts it is the tfl, the thing that orchestrates movement, simple enough.
Вточку! Ублюдок клавиатура ahh Exactly! :happy