Power generation in Yum Chui originates from three sources :-
a) Push / pull piston-like motion of the arms
b) Rotation of the body
c) Thrust off the ground from the rear leg
The pictures below illustrates the process above :-
Below is another view of the power generation process for Yum Chui :-
When you practice the Yum Chui using pads or bags as mentioned in Boji-Lite Module 7 this process will become clearer so do not worry too much about it if it is not clear as this moment.
This is one of those things you have to do to understand rather than sit there and try to intellectually think through it.
End of Module 2, Lesson 4. If you have questions or feedback post them to the BojiLite Learning Group on Facebook.