坐身中正 (sitting upright and balanced)

坐身中正" (sitting upright and balanced) 

In Tai Chi and traditional Chinese internal arts, "坐身中正" (sitting upright and balanced) refers to maintaining a stable and aligned posture while sitting. The key to keeping the upper body straight without excess tension lies in how you distribute your weight.

Where Should Your Weight Fall?

Your weight should fall onto the "sitting bones" (坐骨, ischial tuberosities) rather than the tailbone (尾骨) or the sacrum (骶骨). This allows for:

1. A naturally straight spine without unnecessary stiffness.

2. Relaxed yet active postural support, preventing slouching.

3. Smooth energy flow (氣的流動) for better breathing and internal stability.

How to Sit with "Zhong Zheng" (中正, Upright Balance)?

1. Sit on the ischial tuberosities: Feel your weight resting on the two bony points at the base of your pelvis, not rolling backward onto the sacrum or tailbone.

2. Align the spine naturally: The lower back should maintain its natural curve (not overly arched or collapsed). Avoid forcing an exaggeratedly straight back.

3. Relax the hips and thighs: Let the thighs rest naturally, not gripping or holding tension.

4. Lightly sink the chest (含胸) and gently lift the crown (頂勁): This balances the upper and lower body.

5. Feet placement: If seated on a chair, ensure your feet are flat on the ground and hip-width apart for stability.

Internal Theory (內功理論)

"尾閭中正" (Tailbone centered): The sacrum should remain in a neutral position, neither tilting forward nor backward.

"虛領頂勁" (Lightly lifting the crown): Encourages the natural elongation of the spine.

"氣沉丹田" (Qi sinking to the Dantian): A stable base allows relaxed breathing and better energy circulation.

By sitting in this way, your upper body remains straight yet relaxed, ensuring structural integrity and allowing energy to flow smoothly in Tai Chi or meditation practices.

In Tai Chi, whether to tuck in the tailbone depends on the specific posture and movement, but generally, the tailbone should be naturally aligned, not forcefully tucked.

Key Principles for the Tailbone (尾骨) in Sitting and Standing

1. Neutral Position (尾閭中正)

The tailbone should not be excessively tucked or sticking out.

It aligns naturally with the spine, allowing the Dantian to sink (氣沉丹田) and the spine to stay upright without tension.

2. Light Tucking, Not Forceful (微收尾閭，不過度前傾)

Some Tai Chi styles suggest a slight tucking of the tailbone to avoid excessive lumbar arching (過度腰挺).

However, forcing a strong tuck can cause stiffness in the lower back and block Qi flow.

3. In Sitting (坐姿)

The tailbone should be neutral and supported by the sitting bones (坐骨), not pressing into the seat.

If overly tucked, it rounds the lower back and weakens stability.

If overly arched, it creates tension in the lumbar area.

4. In Standing and Moving (站樁 & 步法)

Song Kua (鬆胯): Relaxing the hips allows the tailbone to naturally align.

"Hang the tailbone" (尾閭懸垂): A subtle feeling of the tailbone dropping naturally instead of being pushed forward.

This balance allows rooting (根) and smooth energy flow from the ground up.

Conclusion: Should You Tuck the Tailbone?

✅ Slight tucking is good for maintaining structure and sinking Qi.

❌ Over-tucking creates tension and stiffness.

➡️ Instead of thinking about "tucking," focus on relaxing the hips (鬆胯), aligning the spine, and allowing the tailbone to settle naturally.