When the body becomes accustomed to moving through the forms in a connected way, the structure of the body will naturally begin to tighten up. As a result, the over exaggerated stretching movements previously used to open up and should be adjusted and made smaller and tighter. The tightened structure of the body forces the feet to become more rooted and the knees and kua to naturally push out even further. As the bows of the legs naturally start to round from the toes to the groin area (normally referred to as the dang), the arms also take on a more rounded shape which runs from the tips of the fingers to the shoulders. The arched spine, or trunk of the body, is connected to the limbs via the joints of the kua and shoulders, two very important sets of joints. When the body is properly arched and connected and working like a gear box, the spine actually becomes the vertical gear shaft connecting both top and bottom.
Remember, all the parts in a gear box must remain connected at all times in order for it to function as a whole. Therefore, the same must be true for the body. In order to be properly locked onto the spine, the shoulders must always be pushed down slightly to the front. The kua joints connect to the spine when the tailbone is tucked in. If at anytime during the forms or push hands the shoulders are raised or the tailbone not tucked in to the front, the connection to the spine is broken and the integrity of the gearbox is ruined.
Because the shoulders are special ball and socket joints, they are able to function as round gears which can move through an unbelievable. If properly conditioned and opened, they are some of the most mobile joints in the human body and can actually move through a full 360 degrees. However, this amazing also makes the shoulders extremely unstable and difficult to control while doing Taijiquan. Logically, if the shoulders and spine are truly connected, even the slightest turn of the spine/torso must affect the shoulders in some way or another. I have observed that every of the spine affects the shoulders in either one of two ways.
The first is that the shoulder joint will lock onto the torso and let the torque and power of the rotating spine swing it like a door on a hinge. In this way, absolutely no movement oris allowed to occur in the shoulder joint. So, when the shoulder locks onto the torso for its free ride, the arm becomes a fixed extension of the spine/torso, and they become one as if they were welded together.
The other possibility is that both the shoulder joint and spine will harmoniously rotate into, or out of each other. In this way, both the spine and shoulders rotate in opposing directions, similar to two gears working in synchronicity. You can say they are separate parts working for the same goal of bringing in, or pushing out the arm.
Because the spine is now working like a long vertical gear shaft that runs from theto the tail bone, every must also similarly affect the two kua. When a practitioner takes a stance and tucks the tailbone in, the two kua connect and “lock gears” onto the spine in the very same way the shoulders connect to the spine when you sink them down to the front. This is why the connected round shaped back is so important in all internal martial arts; because it connects the arms and legs to the trunk of the body and creates a genuine gear box held together by the tension of the conditioned tendons. Because the kua joints either lock onto the spine or turn with it just as the shoulders do, the kua joints are able to open more and more with every of the spine, no matter what direction it rotates. This means that both knees must always be simultaneously pushed out further every time the spine rotates.
This very basic description of the circle should help illustrate how both kua and spine interact with each other in the gearbox. Please keep in mind that describing complex processes that happen in the body can be very difficult to explain in writing.
Once the elbow has been pulled into the ribs during a right sided circle, the waist must then turn left to start the gearbox into motion. As the spine turns left without tossing, the front (right) kua rotates with the spine like two gears working together. This pushes the right kua forward and pushes out the right knee. While the right kua turns with the spine like two gears, the rear (left) kua is locked onto the spine as a single piece and inadvertently gets pushed back to the left. So, one turn of the spine has pushed both knees out in separate directions, stretched out the both kua and pushed them forward. If done properly without tossing, the body should have naturally sunk on a perfect vertical axis. To complete the next step of the circle and initiate the pushing out of the hand, the torso must turn right. As the spine rotates right, the front (right) kua locks on to the spine and is propelled forward one more time. The back (left) kua rotates like a gear with the spine which also pushes this knee back even further. This double stretching out and opening up of the kua pushes everything out to create a straight line on which the energy can flow through with more ease and accuracy.
Because theshould always be fixed on the opponent, any twist of the spine in the opposite direction creates a stretch which literally connects the gearbox/body from to toe.
Just like a mechanical gearbox in which the bulk of its strength and power is produced in theof its gears, the same is true for the body. To train with the knowledge of how to lock the kua and shoulders joints onto the spine and let the gears turn and stretch out the ligaments and tendons is extremely important and beneficial in the final stages of the systematic approach to opening and reconditioning the body. Because the tendons which run through the shoulders, and especially the kua, are not only big and strong but also ceased and hardened, the use of gears to to help them stretch out more speeds up the process considerably.
The top and lower parts of the body are connected through the waist. It seems that the center of the waist is what most practitioners call the dantian. Why is this area so important in Taijiquan? I believe it is because it is the center part of the body where all the tendons from the torso meet the tendons of the legs, including the kua. When a practitioner is able to move connectedly, even a small twist of the torso against the lower body creates tremendous torque and energy. This is similar to winding up a small toy or gearbox; the turning of the crank stores energy inside which is released by rotating in the opposite direction. Because the legs must always be locked into position before the torso turns in the opposite direction, the tendons that connect in the dantian create a locked area which enables the twist to occur. If the bottom part of the body isn’t locked to twist against the top, no energy is produced in the dantian. This seems to be one of the reasons why great masters have always said that the center, or dantian, must never move.
To illustrate this idea, take a rubber band and hook it over the index fingers of each hand. Stretch it out a bit and twist each end in opposite directions. The rubber band naturally crosses in the middle which creates a center connecting the two halves. This center can be compared to the dantian of the body where both halves, top and bottom, meet. If you continue twisting the rubber band in the same direction, you can see that even though the two halves are moving in opposite directions, the center which stores and contains most of the energy, does not actually move. The dantian should therefore be considered the heart of the gear box and the main power center in the body.
When everything in the body begins to work together like a gear box, one realizes that every action or movement in the form is actually powered by ain a different part of the body. At this stage, the inside of the body truly begins to function mechanically. This is an extremely powerful and efficient way of moving and producing energy. While keeping this understanding in mind and consciously breaking down each movement of the forms, every move and can be understood in greater depth. At this stage the practitioner should continuously observe how each of the dantian/waist turns the spine and powers up the limbs to move them.