The waist is also known as the Yao in Chinese. The Yao in Chinese includes the small of the back. The waist in the Tai Chi tradition is not just the waist line (where we used to wear our belts before low cut became popular) but starts at the waist line and is much thicker encompassing more area of your body below this line. It encompasses the Dantien area around the belly button but deeper inside your body. This is your center of gravity. It is your body’s axle.
The waist is your body's axle
Turning from a relaxed waist during your practice you should feel your legs and feet being screwed into the floor while not twisting your knees.
Another way is to imagine a wheel with your Dantien as the axle of the wheel (at the center of your body). When it turns, there is one part of the wheel that bears the weight while the other part of the wheel is empty. Whenever you turn the waist you are effectively emptying one side of the upper body as you fill the other. I go into more details about the substantial and insubstantial weight bearing concepts in the Traditional Basics theory section and I play with it during the weekly flow classes.
All parts of your body are powered by your waist.
This center unites all the parts of the body to help them move together. It is the master of all your movements.
In the beginning
Beginners often move their waist separately from the rest of their body's or they don't move their waist at all. They move other parts of their body like the legs, arms and hands. They struggle to move in a balanced way because they have not engaged their waist. As a result they may hold tension in other parts of the body.
It took me many years to understand what it means to start the movement from the waist. I finally started to click into it through my attempts to teach this important principle in my Traditional Basics workshops. The more I researched to find simple explanations for my students the more I could feel my body centering its gravity around my waist. The movements started to unify and I could feel more power in my steps and upper body applications while feeling more relaxed.
Hips and waist together
As I mentioned in the previous article on proper hip posture, when the lower body is correctly positioned, the upper body can relax. Now I am going to take this further and say that when you can move your body with your waist as the initiator of all movements that is when your upper body can truly soften and relax. You are no longer using the arms to generate energy, your body remains soft and energy circulates freely.
Connecting all parts of the body
When you initiate the movement from your waist you are also connecting your hands and your feet as part of the same body movement. The waist generates energy that is distributed all the way to your hands and your feet at the same time. Even a small movement of the waist can create a large movement in the arms and legs. Once you get familiar with this you will learn to make smaller circles within the bigger sphere of circles. This creates spirals which is the way energy moves in and around your body.
Article referenced from: Tai Chi Health for Life