The most important principle of Tai Chi is to relax completely (sōng, 鬆)^†. Yang Cheng-fu, Cheng Man-ch’ing’s teacher, elaborates on this in “Yang’s Ten Important Points” in “The Essence of T’ai Chi Ch’uan - The Literary Tradition; Annotated Edition” (page 106]: “In practicing T’al Chi Ch’uan the whole body relaxes. Don’t let one ounce of force remain in the blood vessels, bones, and ligaments to tie yourself up. Then you can be agile and able to change.”

In order for us to be “agile and able to change”, we need to stay relaxed and not use force when moving, not just when standing. Cheng Man-ch’ing called out a key aspect of this in Cheng Tzu’s Thirteen Treatises on T’ai Chi Ch’uan (page 76): “T’ai Chi Ch’uan practitioners must place their weight on one foot and change from one foot to the other without using force.”

When we are engaged with a partner, we give ourselves up to follow them; they provide the force so we move without using force ourselves. But how can we move without using force when practicing the solo form? For example, when shifting into the rear leg from Press, how can we get from most of the weight in the front right leg to all of it in the rear left leg without ‘pushing back’ with the right leg? The answer lies in developing a greater internal awareness, relaxing more smoothly and selectively, and being present in each moment during the transition.

It is possible to clench many or all of the leg muscles while standing in a posture, and that is what nearly all beginners do. It’s what I did as a beginner. As we continue to practice, we learn to let go of unnecessary tension, relaxing most muscles completely and only using certain muscles or portions of muscles, including in our legs. This means that we end up with the correct muscles engaged “just so”, achieving a posture in a state of dynamic equilibrium where the minimum of effort maintains the structure we want. When we want to transition from one leg to the other, we don’t need to engage muscles to do so; we don’t need to ‘push off’. By improving our internal awareness we can learn to find and relax the muscles that are preventing gravity from moving our body, letting the dynamic equilibrium continuously change until the transition to the other leg is complete.

Consider shifting into the rear leg from Press. If we relax the muscles in the left leg that are preventing our torso from moving backward and relax the muscles in our right leg that are keeping knee above toe, gravity will pull the right leg down, causing it to mostly straighten out and in doing so move our torso backward. By letting gravity generate the force we can guide the movement, maintaining dynamic equilibrium as gravity moves us. In doing so, we ‘harness’ gravity and it moves us back and over the rear left leg without having to use force to ‘push off’.

This is a subtle activity, and one that represents a significant achievement in mindfullness. First we must have or regain awareness of the muscles involved so we can coordinate the timing of relaxing and engaging them, then we must remain present within each moment of the transition. It takes practice to learn this and incorporate it into the whole form. But it fundamentally changes the quality of our movement, allowing us to more deeply realize the meaning of sōng^† (relax) within the form and in the rest of our lives. It also adds an amazing quality to the experience of performing the form.

† If you have questions about Chinese terms used, you may find About Chinese Terms helpful.