Thought I'd write a quick note on this (since I forgot).
In the Yang style t'ai chi styles I've studied the single hand pushing hands form has been done at just below shoulder level. In this case you push from the shoulder of the pushing hand towards the centre and yielding towards the opposite shoulder of your opponent.
In wudang style the push is directed towards the opponents hip on the same side as the pushing hand. The yield then is directed to the hip on the opposite side.
In the case of the Yang style this is an example of two of the first four powers - ji and lu. The ji is directed at the opponents centre and the opponent is forced to lu (yield or roll back) and direct the force away in order to maintain their balance.
In wudang it is again an exercise in ji and lu, however in this case the exercise strengthens and flexes the kua (the inguinal crease in the hip joint). It is the kua that allows someone to bend at the hips without bending the spine.
