Push pull in archery form (how do you understand expansion NTS)

The term Push-pull is discussed in this episode of Coaches Corner.
Push-pull was a method that use to be taught to archers.
We asked Coach Moore what push-pull was and how it related to expansion in the NTS system.
We have noticed that the term push-pull is no longer used in the USA archery Training program (NTS) as a step in the shot cycle. For more reading on the current explanation. go to the link below and look at the Expansion section.
www.kslinternat...
One of the downfalls that I see in using this the term (Push-pull) is it does not explain which muscles and movements one should use to get the push-pull.