For this exercise, we will focus on the physical muscles surrounding the lower energy center area. This skill, coordinating the movement of the abdominal and back muscles with the movement of the lungs and diaphragm, should be practiced and emphasized on its own. This exercise is one of those pillar principles that should eventually be incorporated into every mind/body prescription throughout the Sunset Tai Chi program. It is ultimately used with every breath you take. Physically, this exercise will allow you to regain control over the abdominal and back muscles. Many of us have lost the firmness and control over those muscles. If you do not use it, you lose it. Starting to move them with the help of your hands, one on the back and one on the abdomen is the first step.

Once you experiment with the movement of your back and abdominal muscles, you will realize that you can choose to move the muscles in or out during inhalation or exhalation. When the muscles move out, it is full moon and when they move inward, it is empty moon. At first, just breathe naturally and deeply with your lungs, and then with the help of your hands move the back and abdominal muscles in and out with only 80% effort. If you move and inhale to 100% it will create tightness in the muscles, which inhibits your circulation. You may initially experience little movement and control over the back and abdominal muscles, especially the back, which moves significantly less. The movement at this stage of training can be compared to the pulsing of the skin of a drum, just moving in and out without much control. As you progress, you will be able to move the muscles while counting 30 levels or stages between full moon and empty moon, meaning that you have developed excellent control over those muscles and can imitate the actual cycle of the moon.

The final idea is not to move quickly from empty to full moon positions but to create as many stages in the movement as possible. Once you are able to create all the different stages of the moon from empty to full, you have very good control over the abdominal and the back muscles. Next, try moving only one side of the abdominal muscles.

Get Started with Empty and Full Moon

At first, you may want to use your hand to help the movement of the abdominal muscles either in the Buddhist or the Taoist breathing. Use your hand to shape the muscles and help you gain back control of those muscles. Many people lose the ability to move the abdominal and back muscles especially around the pubic area and the solar plexus. The back muscles are sometimes particularly difficult to control and move. Over time, by using your palms or your fists, or a partner's, you will gain more and more control over this group of muscles and you will not need the help of your hands.

When moving the abdominal muscles in and out, you will discover that the front abdominal muscles move a lot more than the back muscles. That is because the front muscles have a few more layers of soft tissue than the back ones. The back muscles are very thin and close to the spine. You can easily feel the spine within the soft tissue of the back, but you will have a harder time feeling anything through the front. The front has many more layers than the back.

Even though the front is bigger and has more layers, when you move the back and the front muscles they should both reach empty and full moon at the same time. As the abdominal and the back muscles move in or out, even though the back muscles have a shorter distance to cover, it is your job to make sure that they reach out or in at the same time. If you cannot do this stance, train the movements separately. Train the front muscles and then train the back muscles. Once you are able to isolate and move each group separately, you can then put them together. You will be amazed how quickly you achieve control over those muscles, especially with the help of the hands. Within a few weeks, you may find that you can move the abdominal muscles all the way down from the pubic bone to the solar plexus, emphasizing the movement of front and back at the same time.

Once you have more control over the muscles, you will notice that you can move them in a wave instead of just in and out like the skin of a drum. The more control you have, the easier it is to move them as a ripple or wave. It will also be much easier to move slowly from full moon to empty moon. As you can see, achieving a higher quality with the physical skill of empty and full moon comes down to controlling the front and back muscles in coordination with the breath. This control will lead to our main goals of this skill—strengthening the abdominal and the back muscles while massaging the internal organs, and constantly strengthening the energetic system, especially the lower energy center, or, the center of gravity energy center. This skill will strengthen and upgrade your energetic system, remove stagnation, and increase circulation throughout your entire system. This constant abdominal and back muscle movement will also strengthen what is today popularly referred to as your core.

Slow, Fast, Small, Large Muscle Movements

On some days in your training, you will want to emphasize three to five minutes of intense movement of the abdominal and back muscles. When practicing this way, you are building tension. In order to make efficient progress in regaining control of those muscles, tensing techniques are occasionally needed. The nice part is that when you go back and perform the empty and full moon with only 80% effort, you will find that doing so becomes much easier. You will also experience a larger and better movement throughout the abdominal and the back muscles after these three to five minute intense sessions. Every now and then, just take a few minutes and emphasize vigorous physical empty-full moon breathing.

Buddhist Breathing and Taoist Breathing

When performing the empty-full moon exercise, we can coordinate the breathing with two methods of movement. In Buddhist breathing, we inhale, expand the lungs, and the moon expands at the same time, and when we exhale the moon and lungs contract. The moon and lungs expand and contract at the same time. Inhale slowly into your lungs through the nostrils and, with control, expand through the abdominal and the back muscles. Keep visualizing the lower energy center. Notice how the walls of the abdominal and back muscles move outward away from the visualization of the energy ball at your center of gravity energy center. Eventually, see if you can mentally reside within the energy ball and then 'see' the walls of the front and back muscles moving away from you or where your mind resides.

If you are interested in achieving this skill, you need to take it slow and easy. Work on one, isolated for a while, such as empty full moon. Regain control over the movement of the front and back muscles. Once you are comfortable, move from this skill and emphasize, for a month or two, the visualization of the energy ball at your center of gravity energy center. Once you are comfortable with doing each one separately, put them together. Your mind still may move from the ball visualization when expanding the abdomen, but after some time you will be able to maintain the energy ball visualization while sensing or seeing the walls of the moon moving away from you.

Taoist breathing is the opposite. When inhaling, the lungs expand and at the same time draw the abdominal muscles and the back muscles inward. The lungs expand while the moon contracts and the lungs contract while the moon expands. The diaphragm is in the middle between the two forces. You may feel more tension in the diaphragm area because you have opposite motions within the trunk. That is why, in qigong and tai chi, we hold the thoracic spine slightly forward in a posture referred to in tai chi as turtle back, whereas in yoga we hold the spine slightly straighter. The curving of the spine in the turtle back posture does not misalign the spine. The thoracic spine just slightly relaxes forward to create space for the diaphragm to move down without pressure from the walls of the back and front muscles.

Develop a Healthy Zone

One of the questions I always ask myself is "What is the healthiest and best position of the spine to reduce stress as well as use minimum effort?" Through years of doing both yoga and tai chi, I realized that there is no single position where we should always hold our spine. We want to develop a healthy zone. For this reason, we need to emphasize stretching the spine or the soft tissue around the spine further away from that zone, to all 360 degrees, in order to create a comfortable environment within that zone. Comfortable means there is a lack of the physical stress that pulls on and changes the alignment of the bones and joints. When inhaling in the Taoist breathing method, the lungs expand, and the abdominal and the back muscles slowly draw in while maintaining a visualization of the lower energy center. As you exhale, allow the abdominal and the back muscles to open outward with control until you reach full moon.

(The above excerpt is from Sunset Tai Chi—Simplified Tai Chi for Relaxation and Longevity by Ramel Rones with David Silver)