The spring does not fear the iron hammers strike.
In the style of Xingyi I practice and teach it is necessary to develop the connected and elastic inner body. This can be very hard to do and requires a great deal of dedication and practice. In the beginning the tendency is to feel that one is trying to develope something very foreign and obscure. For instance in the beginning of training Tu Na Si Ba (the four methods of breathing) my teacher would only say "do not use yi (intent) just follow the jin (energy)". But how do you follow something you are not even aware of and cannot feel. Of course I can do the movements and feel the muscles move but that was clearly not what he meant. Only by making a conscious effort to not use the muscles I habitually used was I able to feel the energy moving inside my body. This "no yi" led to the development of greater and greater awareness.
The Chinese use many Taoist ideas to help the student develop this awareness. They are methods of visualization that can help to get the brain out of the way if used correctly. They can also do the opposite leading to over intellectualization instead of body knowledge. When I first read old writings on Chinese internal arts it all seemed almost incomprehensible. Much later after developing some "body knowledge" the same writings seemed very practical.
It took me a long time to realize in a non intellectual way that the inner body was already connected but I can use many methods to get that body knowledge. For example the fascia is a big part of that connection but I would not have to know anything about fascia to feel its development in the body. Someone from the Qin dynasty might describe the feeling of qi throughout the body and talk about the body under the skin as being encased in a web of spiders silk and that would work fine for them. Once I understood that I could grasp that I was developing something that was not foreign to me but that in fact already existed. Something that I could cultivate if I developed enough awareness to physically feel it.
Whatever moves first moves everything.
The body is already connected naturally but we lack awareness and the natural connection is obstructed. Looking for the energy (jin) is to develop awareness so the brain can make the connection stronger. If the shoulder moves first everything moves from the shoulder, if the center moves first everything moves from the center. In looking for the Jin i'm not seeking something that does not already exist and that I am hoping to recognize when it somehow magically occurs. I'm instead becoming aware of something that already exists and through my awareness encouraging it's development. Each time mingmen is stimulated, the mind sends a signal to it to move and that movement moves the whole body. In order for this to happen effectively the muscle tonus must be neither rigid nor soft like a noodle, both of those states will obstruct my awareness and so inhibit my development. If however my tonos is "supple" I will be able to use my awareness to sense where the movement is originated and how the whole body is moved.
The bodies natural state is springy.
If I develope the center as the engine of the body and my mindful awareness strengthens the connections within the body the springy nature becomes apparent and can be cultivated but only if the tonus of the body is supple.