[bts]

The swing plane shifts, either going back or coming down, according to the action(s) employed or the combination of actions employed, for example, the action(s) of the hand(s), arm(s), pivot, lower body and the whole body (shifting the center of gravity) separately, selectively or simultaneously.

For example, shoulder rotation only shifts the plane towards the turnning shoulder plane, which is probably the simplest, naturalest and easiest.