Move the Centre without Collapsing the Axis
The principle is to move your whole body while preserving an upright, adaptable central axis（中軸中正）. Moving forward（前進）does not necessarily require leaning forward（前傾）: the body can advance through coordinated movement of the legs, hips, and feet while the trunk remains comfortably aligned.
However, uprightness（中正）is not the same as rigid verticality（僵直）, and a slight inclination is not automatically a mistake.
1. Moving the axis versus bending the axis
Imagine carrying a pole upright: you can move it forward, backward, or sideways without tipping it. In Tai Chi, this is a useful image for whole-body translation（整體平移）.
The body is more complex than a pole. The ankles, knees, and hips continually adjust to maintain balance. The aim is to preserve the relationship between the head, rib cage, and pelvis（頭、胸廓、骨盆）, while allowing the limbs to move freely.
| Movement | What happens |
|---|---|
| Whole-body advance（整體前進） | The pelvis and trunk travel forward together, supported by the legs. |
| Forward leaning（身體前傾） | The trunk inclines forward; this can be coordinated or excessive. |
| Bending at the waist（折腰） | The upper body folds forward relative to the pelvis, potentially disrupting its connection to the lower body. |
| Reaching with the shoulders（探肩） | The shoulders and hands advance farther than the supporting body can comfortably follow. |
The important distinction is between moving your centre toward the action and reaching beyond your support.
2. Why do people bend forward when pushing?
Often, they are trying to make the hands travel farther without sufficiently moving the pelvis or adjusting the feet. The shoulders advance, the hips remain behind, and the torso inclines or folds.
Another possibility is that they deliberately use body weight（體重）to assist the push. This can produce effective force; leaning is not inherently mechanically wrong. But it can also increase dependence on the partner’s resistance（依賴對方支撐）.
A useful question is:
If the partner suddenly yields, can I remain balanced and change direction?（對方突然退讓，我能否保持平衡並轉換？）
If the practitioner falls forward or must take an uncontrolled recovery step, the push has exceeded their available support.
3. How can you push while remaining upright?
For a forward An（前按）, think of this coordination:
- The feet interact with the ground（腳與地面作用）.
- The legs move and support the pelvis（腿帶動並支撐骨盆）.
- The trunk travels with the pelvis（軀幹隨骨盆前移）.
- The arms transmit the action while retaining comfortable structure（手臂傳力、保持舒展）.
The hands may adjust relative to the body; they do not have to be frozen in place. But they should remain coordinated with the body’s movement（身手協調）.
“Bring the body forward to support the hands”（身進以支持手）, rather than merely extending the hands farther, is a useful teaching cue.
4. What is the classical basis?
The Insights into the Practice of the Thirteen Postures（《十三勢行功心解》）states:
「立身須中正安舒，支撐八面。」
Maintain a centred, upright, comfortable posture, with support in all directions.
The word comfortable（安舒） matters: the posture should allow adjustment, rather than being held stiffly. www.ct-taichi.org.tw
The Tai Chi Treatise（《太極拳論》）also pairs balanced standing with wheel-like mobility: 「立如平準，活似車輪」. My interpretation is that alignment should preserve your ability to respond in different directions—not merely help you withstand or deliver one forward push. www.ftcca.org.tw
For teaching, I would phrase it:
“Move the centre without collapsing the axis; stay upright without becoming stiff.”（移動重心，不折中軸；保持中正，不落僵直。）
A slight whole-body inclination can still be coordinated. The more significant faults are collapsing at the waist（折腰）, overreaching（過伸）, and losing the ability to change（失去轉換能力）.