There is possible alternative word for “posture”. That is “placing”, and it means “place the body like an object (a relatively slender object)”. This is the word I use for carrying out an advantageous condition of supporting the body. Actually this is a key technique for my AT lesson.
Many people are holding their body in excess while they are doing something or just standing/sitting. This means that they have a habit of giving excess co-contraction at the major joints in the axial body in order to support the body. Or in other word, they can still support their body in exactly the same position(posture) with less muscular contraction.
And this ‘Holding’ is different from ‘placing’. A person whose posture is good (advantageous) can ‘hold’ their body in excess. The person may not prevent back ache or neck ache with that. But, if the person intend ‘place own body like an object’ with still in good posture, the person will be likely able to release excess muscle contraction.
This is what we do by using the Alexander Technique, and this is my opinion. Our one of key technique is the primary control, and what we do in the primary control is to try to support our body like a just placed object without holding too much. Well, I think that the primary control has shortcoming because it covers part of the whole body (it is more about the head-neck-torso relationship and not about the head-neck-torso-leg-ground replationship).
Anyway, I strongly believe that we get what we want to get if we have clearer goal or objective. So what we intend is really important. The outcome by intending ‘placing’ is different from the outcome by intending ‘the head forward and up, neck to be free, back lengthen and widen’. Ordinary directions are just a process of the true objective, and we should intend the true objective. I think that the word ‘placing’ will be good candidate to use. By the way, I described this in detail and my hypothetical theory in my blog. You may like this: http://www.ai.alexlesson.com/an-advantageous-way-of-using-our-body/
There is the term ‘grounding’, and people in body work often use it. I saw pictures of a big tree many times when people are trying to get image of ‘grounding’, with maybe saying “we should ground like trees”. Well, this help us to some extent, but I think that this is actually not for human’s case. There are two ways objects on the earth can ground. One is with root or pile, and the other one is just placed on the surface. (Maybe we have some other, like hooked or leaned.) We are the latter and ground with placed on the surface without any root or pile. So, given that ‘grounding’ has two different types in it, ‘placing’ will be more specific and will be more helpful for us to adapt to the reality.