Depending on the company, I'd love to give it a try, but Karen was right.... you are eligable for a GOOD ergonomic chair. Not just one they label as ergonomic, but one that IS. Since I do this all day long for my job, here's what you'll need to ask for (then have them come to ME to buy the chair )You'll need lumbar support, front knee and back tilt, adjustable arm rests. You should also have foot rests (believe me, they make a huge difference!) and a good articulating keyboard tray with mouse rest on the same mechanism.

If they don't accomodate you, then they ar not followig the rules of the ADA and can be fined. Don't feel shy about reporting them if they decline your requests! This is your long term health we're talking about, and if they wat you, the $500 they put out for the chair, keyboard, etc. is minimal for a great long-term employee.