From the center of your body you cultivate a feeling of drawing energy into yourself and condensing at your center. Then you recognize the expansion at the lower back as you exhale from your center. You have a physical center of mass and a feeling center of gravity. You condense to that center and expand from that center.

On the inhale condense on the front and yin lines to the abdomen. On the exhale expand the lower back and kidney area using the back and yang lines. On the inhale condense on the front and yin lines to the dan-tian (abdomen) and sink. On the exhale expand the ming-men (lower back and kidney area) using the back and yang lines, push up and vertically align on the back line..