"Tai Chi is not about learning. It is about un-learning. It is the ultimate method of no method." - J.F.

The training of "Shen Yi Chi", for explanation see below.

Tai Chi was designed as a very effective internal fighting art. The aim is to train you to use your spirit (Shen), mind (Yi) and energy (Chi)* instead of brute forces derived from muscular strength. Therefore, no matter what body size you have, your age, or whether you are  a man or a woman, you could develop a high level of power and skills if you do Tai Chi properly. Health benefit is the direct result of your Shen Yi Chi training.

Tai Chi is NOT about learning a sequence of movements and repeating it over and over again. It is all about training your Shen Yi Chi. The movements are just a method to help you train the Shen Yi Chi. Much like, doing algebra as a method to train and express the underlying mathematic principles. And once the Shen Yi Chi are well refined, your skills and power will increase no matter what style of Tai Chi or Martial Art you do!

How do you train Shen Yi Chi (Spirit/Mind/Energy)?

There are 3 regions governing Shen Yi Chi. Referring to the picture above, the green spot (Shen Ting) governs the Shen, orange spot (Shien Zhong) governs the Yi, and blue spot (Chi Hai) governs the Chi. The 3 elements must unite otherwise you would be practicing in vain. When the 3 elements unite, the energy field appears, represented by the yellow glow, and you would use these invisible elements to guide your movements, to fight, and to nurture your body to make yourself healthy.

If you practice Tai Chi without understanding the concept of how to unite the 3 elements you are basically wasting your time. You are just learning how to "dance in slow motion." Of course, one would still get some health benefits from dancing in slow motion, but you are not really doing Tai Chi.

How does Tai Chi improve your health?

In Chinese Medicine, virtually everything is associated with the flow of Chi. Tai Chi training helps you unblock all your Chi channels, making the flow smoother. Plus, it teaches you how to replenish your Chi when your energy is low. And to replace muddled Chi with clean fresh Chi. Being able to manipulate Chi yourself also puts you in control of the flow and be able regulate the flow if there are disruptions.

*nb: some schools call "Shen Yi Chi" as "Jing Chi Shen", which is just a different approach to a very similar concept