See if I'm interpreting what you said properly... The momentum that keeps the rotation going comes from the forward movement of the forward-moving partner. If you are the backward-moving partner, one of your responsibilities is to not block the path of the forward-moving partner. If you do, the forward-moving partner can't get any drive and the rotation will lose momentum. I've also observed that a whole lot of people who do pivots just will not step into the partner, for some reason. You've got to get those legs intertwined; otherwise you don't have a common axis of rotation and the whole thing deadlocks.