So, what advice can I give regarding chairs? First, don't look to a chair as the primary solution to poor posture - remember it's your posture and so it's you that has to learn how to change it. But if you have a choice, I recommend very simple, basic designs - fairly flat, reasonably firm bottoms and backs that do not force your torso into any particular shape.
In addition, there's a lot to be said for having your knees at a lower height that your hips. This tends to encourage the natural "double C" curvature of your spine that provides easy upright support for your body. The simplest way to do this is to use a stool whose base is higher than the typical chair when you can. My students are often skeptical when I recommend this ("There's no backrest!) but most of those who try it for a few days report feeling far more comfortable once they get used to the added height.
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Nowhere is the interplay of ergonomic and Alexander Technique concepts better illustrated than in the design of the chair, and the ways in which we use them. The Chair: Rethinking Culture, Body and Design provides a wonderfully fresh look at an object so common in our society that most of us pay little or no attention to it. Galen Cranz, a professor of architecture at the University of California Berkeley and a teacher of the Alexander Technique, has written what is probably the definitive work on this topic. Everybody who sits on chairs can learn a great deal from this very readable book. You can order this book at the Alexander Technique Bookstore at http://www.alexandertechnique.com/books
