Good post Tiny.
Adding to that (and to complicate things further for you OP, see, it wasn't as simple as you thought ;) ), the restriction of faster movement when you apply leg should actually come from your seat, far more so than the bit. You'd seat is THE single most important aspect of putting a horse on the bit and beginning collection. It dictates the pace, tempo, rhythm and manages the half halts to fine tube the shape of the horses body and how he is using it.
Simply putting leg on and pulling on the reins will just give you a cranky horse. Posted via Mobile Device