Taoist practice oftentimes use reverse engineering, both as physical treatment strategy and spiritual enlightenment strategy. To understand the concept better, in this post I shall use the condition of Carpal Tunnel Syndrome as an example.
The Phalen Test (see video below) is that standard test of Carpal Tunnel Syndrome. Those who feel pain or numb while doing the test indicate a condition of carpel tunnel syndrome. Using chi-kung as a healing practice, one should "approach" the form as close as possible BUT without feeling pain, AND with a feeling of numbness. Using this "personal form" as the starting point, one should allow this numbing sensation to follow from the fingers and thumbs, passing through the end-positions of the fingers, through the wrists, up the forearms, up the triceps and then all the way joining the ball-and-socket shoulders joints. With this muscles-as-one, one should do zhan zhuang in either seated or standing form (as one may prefer), one should "enjoy" the numbing sensation while doing zhan zhuang as stated. With progress, one should be able to improve minutely, step by step to the "standard" testing positions, with a numbing sensation but without feeling pain.
In the forward deteriorating process, it is delimiting one's degree of freedom with feeling of numbing to pain. In chi-kung reverse engineering, it is increasing one's degree of freedom using numbing sensation and chi-connectedness (or a feeling of muscles-as-one) as one's guiding sensation.
This approach philosophy applies to other chi-kung healing methods. Try and experiment by yourself, its fun!