I don't have a chair.
I took some classes with Harriet Hargrave and she started one class talking about ergonomics. She told us what chair she uses. I had already had one back surgery and was conscious of the need for a good sewing environment. [Remember she sewing machine quilts all her quilts.] Well, her chair was costly and luckily didn't fit me. So I saw what the personnel at the office furniture store were using: a swopper. I talked them into letting me try it out over a weekend, went in with it Monday, and bought a new one. It is like sitting on a stable balance ball. It has no wheels. I have it on a throw rug. I love it.
ali