Straight Body Line and Vertical Stright Line

Straight Body Line and Vertical Stright Line

For ordinary left and right turns, I would use an upright, relaxed central axis（中正）as the foundation, while allowing a gentle bow-like quality in the back. These two qualities can coexist.

The important distinction is between an upright axis and a rigidly straight spine. Your spine has natural curves; you do not need to flatten them or force the crown and tailbone onto a geometrically exact line.

Your two descriptions	How I would interpret them
Crown and tailbone aligned vertically	A useful image for lengthening the body and preventing leaning, provided the neck, waist, and hips remain relaxed.
A slight bow with an imaginary vertical line in front	Can be useful if the line represents the bow’s “string,” and the back stays gently rounded and spacious. It becomes unhelpful if you hunch, project your head forward, or push your pelvis forward to create the shape.

Yang Chengfu’s essentials combine 虛領頂勁—a gently suspended crown—with 含胸拔背—a reserved chest and slightly rounded back—and 鬆腰, a relaxed waist. Thus, uprightness does not require a stiff, flat back. 

When turning, try these practical cues:

• Crown floats upward; pelvis settles downward（頂懸、胯沉）. Avoid forcibly tucking the tailbone.

• Let the waist and hip joints coordinate the turn（腰胯帶動）. Do not twist only the shoulders against a locked pelvis.

• Keep the chest soft and the back broad（含胸拔背）. The bow should feel elastic, with room to breathe.

• Keep your balance as your weight shifts（虛實分明）. Your central axis can move with you; it need not remain fixed over one spot on the floor.

My preferred cue is: “Turn with a tall, supple body—中正而不僵，圓活而不塌.”

A gently curved body can be good for turning. Curvature itself is not the problem; forced bending or stiffness is. My earlier wording may have made that unclear.

If your crown and tailbone remain broadly aligned, while your back forms a gentle bow behind that imaginary line, you can still turn smoothly with central uprightness（中正）.

Distinguish these two situations:

• Gentle, elastic rounding（含胸拔背）: your chest is relaxed, your back broad, and your waist and kua move freely. This is compatible with turning.

• Deliberate hunching or holding a rigid bow（彎腰駝背、僵住）: you force the shape and restrict your movement. This can interfere with turning.

You do not need to straighten out the gentle bow before turning. Let your waist and kua lead, with the torso following as a connected, adaptable whole（腰胯帶動、上下相隨）. A more pronounced curve is not automatically better.

Yes—you can yield at the belly, allow some bending, and then recover to express force. That is a possible receiving-and-returning action（蓄發）, but bending a lot and then straightening does not by itself create peng（掤勁）.

I should clarify my earlier explanation: 中正 is dynamic balance and organization, not a requirement to keep one fixed vertical shape throughout contact.

When someone pushes your abdomen, there are two different possibilities:

Receiving the push	What happens when you return
Connected yielding（鬆化）: your hips fold, weight shifts, and torso adapts while your legs continue supporting you.	Coordinated pressure through the feet, legs, hips, and torso can return force to the partner.
Local collapse（塌陷）: your belly caves in while your pelvis stays fixed and your upper body folds.	You must first recover your structure; straightening may become an isolated muscular shove.

Peng should remain present while you yield, as an adaptable, expansive support—not only appear when you straighten. You give the incoming pressure somewhere to go without losing your whole-body connection（貫串）.

The bow analogy is useful here: the bow changes shape under load but retains support and tension throughout. Your body, however, also uses active muscular coordination; it is not simply a passive spring.

So your idea can work, with this refinement: receive through the whole body, then return through the whole body（整體蓄、整體發）. A deeper bend is not necessarily more powerful, and the return need not finish with a completely straight torso.