Brady Riggs from golf.com did a video on the power move, particularly made popular by Tiger Woods.
But i like how he goes into showing that you load up the left leg, then holding that force until its transfered through the kenetic chain into the clubhead before impact.
I am not sure if the belt buckle area is a key indicator of this power move or not, to me its a timing thing, holding that flexion in the left knee until the optimal moment then explode upward.
