In the practice of internal martial art (zhan zhuang and tai-chi), it is important for a practitioner's body to have a total overhaul, with the objective of building a strong foundation. This complete overhaul should be done after an initial stage of a feel of chi or jing (a martial art term: 開始懂勁）. And the martial art term for Total-body-change is "Change jing" 換勁.
I can't stress more that importance of Total-body-change or Change-jing. Without this process, any progress in martial art training is impossible. Why? Because strong structure with effective power (jing) transmission is only possible only after the process has been done. What is this structure all about? It is a combination of effective alignment plus the ability to channel chi (or jing) along desired muscle paths for generation of martial power. After the process, the power is still not there, but the structural foundation and ability to transmit chi are there, which are essential for further power training of the discipline of internal martial art.
How then can this kind of tune-up be achieved? My experience is that the best way is through a "sweating" course of intensive zhan zhuang. The prerequisite foundation practice is an introduction program of zhan zhuang (i.e. able to feel chi, and able to generate and balance chi). In an intense zhan zhuang training, a practitioner is to do zhan zhuang for half to one hour in one session, with two sessions for day, and for a period of two weeks. In a typical training session, after about half an hour, a practitioner's muscles for standing will become tired and fatigue. And in turn, his chi will be boosted up to fill his "sleeping" or otherwise-relaxed muscles to compensate for his fatigued regular standing muscles. A practitioner will usually be sweating all over (well, except when he is practicing in an air-conditioned room), and he can feel his chi all over his body, as if all his muscles become a single mass (肌肉如一)!
It is interesting to look at the practice of Neidan (Taoist yoga) in this perspective. Neidan is said to train up one's body and then mind and then a combination of the two under one's new and enlightened self. My suggestion is that Neidan practitioner can, like one martial art practitioner of the internal type, benefit a lot from a program of Total-body-change. It is unfortunately that most (seated meditation only) Taoist Neidan practitioners like a more relaxed (lazy?) approach!