Is this not an example of where using japanese instead of equally useful english confused the meaning of the sentence? the japanese shisei and the english posture or stance is the same, and therefore I don't see any reason to use shisei in the first place.
Why stop there? why not throw out all the japanese and replace the lot with english.
Throw out the silly uniform, dresses and dumb ettiquette too.
And mats...no one has mats in the street...lets get rid of those too.
And so it goes on.
Of course changing language might not help when you have french, poles, belgians et al in classes.
Heres what Tamura Sensei had to say about Shisei
Shisei is translated in English by: "position", "attitude" or "posture".
Sugata (Shi) means the "form", figure" or "stature". lkioi (Sei) signifies energy, vigour and vivacity. Shisei combines these meanings.
But the meaning of Shisei not only describes an exterior attitude; good form, deportment and bearing; but also an interior force visible from the outside in its external manifestations. For example, the vitality of a child is apparent from its vivacity, its bright eyes and its active movement.
How do we reach this Shisei? First, we must re-order the body which is like a vase containing Ki. To do this, the spinal column is extended and straight. If you feel that you are pushing the sky with your head, your spinal column will extend naturally. Be careful not to puff out your chest in a military manner. The shoulders should be relaxed, falling smoothly, the small of the back is not bent, the Ki is comfortably positioned in the Seika Tanden and the whole body is comfortably relaxed.
The great exponent of the sword, Miyamoto Musashi, says on the subject of martial Shisei:
"The face is calm, neither turned upwards, downwards or to the side; the eyes slightly closed without movement of the eyeballs; the brow unwrinkled; the eyebrows slightly gathered, the bridge of the nose straight; the chin neither stuck out or drawn in too much; the nape of the neck equally straight and the spinal column full of energy. Below the dropped shoulders the body is perfectly relaxed; the spinal column is in place; the buttocks drawn in; the legs, from the knees to the ankles are firmly set on the ground; the hips are not twisted; the stomach is firmly shaped".
In Aikido this is called "Sankakutai", a supple, balanced posture allowing free movement; a regular tetrahedron which is a cone from the side.