[JeremyNT]

I think the real solution here is diversity. I don't know that 9-5 standing was ever seriously advocated as a preferable alternative to sitting; clearly there are issues with that too.

I mix things up at work personally; about a third of the day standing, a third sitting in a chair, a third sitting on a yoga ball. At this point it seems like you should just hedge and try to about doing any single thing without moving for too long.