[daveungerer]

http://en.wikipedia.org/wiki/Ball_Chair

A ball chair is not an exercise ball chair. Looking at the illustration on Wikipedia, it's clear that a ball chair forces a C-shaped spine. Your spine will stay in an S-shape if you sit upright on the "chair" I'm referring to.

[Avshalom]

Seeing as that design is never mentioned in respects to ergonomics and certainly wouldn't "bounce" anything, I strongly suspect the quoted passage was referring to the inflated balls you sit on.

[daveungerer]

You're right. That's one of the disadvantages of linking to the printer friendly version of an article. You miss out on those "link" things that made this "interweb" thing famous:

http://images.businessweek.com/mz/10/19/0509_chairs.pdf

I'm just going to continue as usual, using the ball chair and alternating with a normal chair if needed. My spine feels great and definitely has a more natural shape when sitting on the ball vs. a normal chair.