True internal power is not just using the rear foot to push off the ground to generate power. Instead, true internal power is tapping the power from the ground and running it through the body before exiting the striking hand into opponent’s body.

The video below illustrates this principle :-

Close up of the internal process (if you can’t see it its because its “internal” get it?) :-

Internal training involves feeling carefully what is happening inside the body. Just externally moving the body is not internal. Moving the power through the nine crooked pearls is true internal power.