Understand the capability of "Dan Tien"

 Understand the capability of Dan Tien

I  don`t understand when using internal movement how do you keep your abdomen loose, or is that myth not true.(Maurice B.) 

I am finding the Tai Chi Walk difficult probably due to my having to break old habits with the Yang Style. But it is coming along. The step backward is awkward in that I find it hard to keep my buttocks tightly in and pivot at the same time. (Jim D.)

 Master Stephen Hwa:  The sit back move requires you to fully tuck in the behind by energizing the abdomen and at the same time you have to be able to turn at the waist with ease and with power to ward off opponent' s attack (see Figure 9). 

                                            Figure 9

The above examples illustrate that the Dantian has to be able to do multitasking. One has to understand that energizing the Dantian for certain move is different from tensing up the Dantian. Tensing or stiffening the Dantian immobilizes the entire section of that part of the body indiscriminately. Energizing is a selective utilization of certain muscle for a certain function. Energizing has the character of agility, sudden surge and ebb not static.

Even "tuck in", also called "stretch down tailbone" should be fluid in nature. So, even one is fully tucked in, one should still have the feeling of suppleness (pronounced "soong" in Chinese) at the Dantian. A simple picture of what is going on during the sit back and ward off movements mentioned above could be as follows: 

The tuck in move uses the Rectus Abdominis muscle, while the turning move uses the the External and Internal Obliques. Even though both muscles are next to each other in the same region, with the yin-yang training in tai chi, one should be able to use its distinctive feature independent of each other or in cooperation with each other. All those attributes mentioned above can be developed by practicing the Tai Chi Form. I have seen this among my students.