Hi,
As long as I am visiting, I will take this one!
No, the opposite doesn't hold true, as far as lowering your arms. There is a point on the bottoms of your feet that is a primary point, that connects to the kidney channel. In bouncing, you are stimulating that point, and the kidneys. So in essence, you stimulate the kidneys, whether your hands are up or down.
Many things within your practice stimulate the kidneys. Sword fingers to kidneys, small universe breathing into the kidney area, lower dan tien focus/breathing feeds the kidneys, patting and rubbing the kidneys in harvesting qi, etc.. The 'bottom of the torso' is a different deal. It isn't a primary organ like the lungs or kidneys. It is an energy point, or gate.. Other than relaxing oneself, that point included, it isn't specifically effected through this action of lowering or raising the arms.
love,
gallen
