Ergonomic chairs should be required equipment for all office workers.
I have a lower back injury, discs L3 and L4 are bulging.
So, my doctor wrote a note to give to my employer requesting that they purchase me an ergonomic chair. It makes a HUGE difference in remaining comfortable. In fact using an ergonomic chair is the difference between being in pain, or being comfortable.
Mine is called a "C-pod" and it is really comfy, I dig it.