2020 09 09 13h59m28s Classical Tai Chi Forum 16 tai chi walking mp4
The last move involves primarily the use of the power of the core (described as contracting abdominal muscle inward) together with the pull of the lead foot to move the body. This is the crucial step for converting the walking motion into an entirely internal movement. Notice Geri Shea's abdominal motion it is very clear to see as she "contracts" in order to pull forward and back.
via YouTube https://www.youtube.com/watch?v=V2LmfniUX-M