This posture is Tai Chi. It is considered to be the most powerful of all the tai chi (taiji) and qigong (chi kung) postures, and is often used as a separate exercise to increase leg strength, concentration, deep breathing and chi (qi) flow.
Zhan Zhuang means “standing like a tree” and is roughly pronounced “Jan Juang”, or, in southern China, “Jam Jong”. For most people, training in Zhan Zhuang is a complete surprise in the beginning. There are no recognizable external movements, although it is a highly energetic exercise system. In contrast to many other methods, Zhan Zhuang develops our internal energy in a very efficient way, instead of consuming it.
Zhan Zhuang is practiced in well-balanced standing positions which increase the flow of energy and build up internal strength. The Zhan Zhuang system is based on a unique combination of exertion and relaxation which stimulates, cleanses and internally massages the whole organism.
Stand with your feet shoulder-width, and parallel. Bend your knees just slightly (feeling the backs of the knees as soft and hollow), allowing your weight to sink fully into your feet at the bubbling well – the hollow spot center and just below the upper pad area, legs and pelvis are relaxed. Gently roll the knees out a bit without moving the feet. This will tend to lift the arch. Don’t allow the big toes to lose contact with the floor. Then float your hands and elbows up to the level of your heart – elbows lower than wrists, palms facing your torso, creating a circle with your arms, with four or five inches between the gently extended fingers of your right & left hands – just as though you were indeed hugging a tree. Sink the shoulders down. And then imagine that you are hugging that tree, and as you hug the tree you’re also becoming a tree: feel your roots descending, sap being drawn upward through the center of your torso, your arms & legs lengthening, your crown of your head softening to receive sunlight and the energy of the sky from above you. Use inhalation to expand body and exhalation to release unnecessary tension down into the ground using the bones as conduits. Continue to feel your limbs energize, your spine elongate and your muscles relax into the position. Hold for some time.
Slowly, with practice over time, work toward sinking lower, widening the distance between the feet (still kept parallel), and holding for longer periods of time. The body will relax into the pose, your mind will cease wandering and your muscles and tendons will become more flexible and supple. This should not hurt your knees or lower back if done correctly. If it hurts the front of the thighs (quadriceps), that is a good sign.