This sinking is like the calm before the storm, the end of the out-breath before the In-breath, the moment before the dawn chorus begins, the moment when a horse is about to tackle a jump. It is a moment of calm, but also of anticipation; of rest, but also of gathering; of release, but also of potential…. like the compression of a dropped ball as it lands before bouncing upwards again, or a sailing boat during the moment of tacking before the wind catches the sail again.
The initial action doesn’t exactly cease, but softens to allow in the relaxation, sinking, release, rest, or calmness. You could also see it as the momentum of the initial movement being allowed to die away naturally and, because it naturally sinks, it becomes like a spring loading up prior to releasing into the new movement. On the theoretical level, it is the interchange of yin and yang.
This doesn’t mean that people perform taiji like frogs bouncing up and down, and if it is done this way it means that the concept has been externalised… This is something that you can only produce when you feel it in every fibre of your being. I say feel because, superficially, you can mimic it, or make it look to an outsider as though this is what you are doing… acting the part, but when you do so without feeling it in every cell, you won’t be moving with ease, and your energy won’t sink completely. In the Alexander Technique this has been described as ‘free movement’; movement that is unencumbered by any tension or ‘holding’ by muscles in the body – something that we generally don’t do comfortably.
In taiji it’s one of the hardest things for most people to allow to happen; in other words, the mechanical action is easy to emulate, but feeling it can be tricky because most people are busy making sure that their limbs are in the correct position, the body is turning as it should be, the head is held in the correct position, the eyes are looking where they should be, the weight is on the correct foot… etc. etc. Which, of course, is why we practise a taiji form over and over again, because only when you are absolutely familiar with it can you see what lies inside the movements.
So, as you change from one posture to another, at the appropriate places, allow the muscles to release and soften, allow the sinking of the qi to take place, allow the cells of the entire body to relax, and, combined with the intention behind the movement, movement itself suddenly becomes free, fluid, coordinated, and comfortable as you move exactly as the body was intended to move.