Aloha and greetings from Maui.
Here's the second excerpt from the "Zhan Zhuang Wisdom - The Breath of Life" article. Mahalo.
THE VERTICAL ASPECT - CROSSING BREATHThe first of the three dimensional aspects of the triad of Sphericality (Height, Width and Depth) that we shall explore is the vertical or height aspect. The ‘Crossing Breath’ develops this. The idea is simple. Breathe into your upper back and lower abdomen. The breath from the upper back descends to the sacral region while the breath starting at the Low Dan Tien or navel area simultaneously ascends to the Clavicle. Half-way down and up the twin aspects ‘cross,’ hence the name.’
In addition to refining the vertical motions of down and up individually, the Crossing Breath begins to train the muscles to move in opposite directions or contrary motion; an essential characteristic of Spherical Breathing.’ The idea of opposite motion is also especially useful in the area of the midriff, and specifically between the External and Internal Obliques who’s job it is to move in opposite directions during proper Taiji, Qigong and of course Zhan Zhuang practices.