I missed the tai chi class about shifting body weight.  I continued to miss this class for over 30 years until encountering Master Stephen Hwa’s teaching.  “The most important step is when you are stepping forward the body weight does not go with the foot until the foot is on the ground and then bring the body weight forward… engaging our core muscle … to pull on the leading foot so you are pulling yourself forward ….”  Master Hwa explaining pull forward movement 

I can choose to pull or push.  Shifting to a pull forward movement model remedied years of nagging leg sciatic nerve pain.  Pain that would ebb and flow  and yet got worse over time despite increasing  tai chi practice.  I thought it impossible that my tai chi  was the root of the nerve pain.  In hindsight, tai chi was not the problem, it was me pushed my body mass and jamming muscles, tendons, ligaments together cause nerve irritation.  Pulling opens the tissue much as pulling opens the space between a bow’s stave and string.  It is useful to think of the human as a single strut bow tensegrity structure.  

 Missing class summary:

A body is everything inside its form and has mass.  A force is the agent changing movement between the bodies.  Force can be external or internal.  Force has direction and magnitude.  Force can be push or pull.  Force  applied behind the body  is Push.  Force applied in front of the body is Pull.  Gravity is a pull force from Earth’s mass and pulls my centre of mass to it’s centre.  Applied force requires contact with  Earth’ s surface to move my body’s mass from here to there .  Proprioception is our sense of body position, force, and movement and we feel the  applied force as weight or pressure through feet and other contact points.      Skeletal muscle contraction create the internal force applied through contact with Earth’s surface.