In the longer forms of Tai Chi this form features later in the form. In the modern simplified 24 step Yang form is features right at the beginning. I'm a fan of teaching people this form early on as it does wonders for your lungs, nervous system and core stability.
Check out the video where I demonstrate the form and theres also a video showing the movement of the diaphragm which is useful to understand as this form really helps you to open and stretch your diaphragm in all directions.
6 key benefits
1. The action of the form increases all round expansion of the diaphragm which opens and closes the ribs, increases lung capacity and massages the internal organs.
2. The diaphragm connects to the 1st, 2nd and 3rd vertebrae of the lower spine, which each deep breath and motion the lower spine is mobilsed
3. The motion massages the lungs and internal organs in the torso
4. Improves core stablisation for postural stability
5. Calms the nervous system
6. Great self defence applications for close range combat