I took a quilting class with Harriet Hargrave. The whole first portion of the class was on ergonomics. She used a Hermann Miller aeron chair. I went and looked at them. $$$ The secretaries at that store all used the Swopper. I talked my way into them letting me use it over a long weekend. I bought one. Look it up on the web, probably at www.sit4less.com It is like sitting on a balance ball so that I keep good posture. It adjusts for height. A bit pricey but well worth it in comfort. Good when you have arthritis and such.
Gads, I just checked ... and the price really went up. Still I love mine.