Ok, in this post I am going to really get right into it. If there are any thoughts, I would suggest re-reading this post and then practicing what I mentioned (the concepts, not the techniques). If there is further doubt, shoot a comment and I will attempt to answer as best as I can (based on my level of experience and understanding).
Standing practice is often touted in internal martial arts as a means to build or sink chi and eventually transform the body into a mechanism where chi can disrupt another person through means of relaxation. But why is it so important? What exactly is the mechanism that enables power to be generated?
I would answer, based on the observations from my experience, that it is the creating the meridians or lines that enable one to withstand muscular (or other types) of force and simultaneously direct that force to the opponent/ opposition.
When one stands and consciously releases, all the weight has to go somewhere. In Tai Chi, this weight is sink to the ground. In CST Wing Chun, I have been told that the weight does not go below the knees because of the need to be “light-footed.” Regardless of where the weight is being dropped, certain lines or meridians are created. It is similar to rivers forming pathways to oceans. Even if those rivers are dried up, if they were to be filled up again – as it so happens in flash floods – then the pathway is used. This is because of the carving of the pathway by the force. So, in essence, what is done by the release of the weight in the body is that meridians or lines are created or carved into the body and this enables force to be absorbed or directed.
Sinking the chi is also important because it allows for the accumulation and then the subsequent release of that energy. It is needed as fuel for the absorption and utilization of energetic force. Standing is also important because it is the only avenue one can do this. In most other cases, one is conditioning, practicing drills or engaging in partner drills. One can also do this in forms but forms have too much external movement vs only standing so it is very tricky and time-consuming to achieve the same state just by doing the form.
Remember, people have not been taught how to use the body from the get-go. Either there is arrogance on the part of the person (or immaturity of the kid) or there is ignorance on what to do (lack of a proper teacher). Because of this, one has to re-learn what to do. It is this re-learning that requires one to practice standing.