My understanding is that any position for too long becomes un-ergonomic, and really our bodies crave variability. I do my most productive coding on my couch in a weird slouching position, but I try not to do it for too long. I'll frequently switch back to my desk, and then try and take as many calls as possibly walking around the neighborhood. I can't focus on code at a standing desk or sitting on a yoga ball or whatever other people prescribe, but if you can throw that into your mix go for it, but sitting on a yoga ball all day is probably as deleterious as doing anything else all day.
There are definitely different ways to use your body with different effects, but I think the problem is over use of any specific form.
There are definitely different ways to use your body with different effects, but I think the problem is over use of any specific form.