I second this. I try to sit on an exercise ball as much as possible at work (sitting, bouncing, stretching on it). I can't usually make it for a full 8-10 hour

I second this. I try to sit on an exercise ball as much as possible at work (sitting, bouncing, stretching on it). I can't usually make it for a full 8-10 hour day, so I usually switch to a regular chair with back rest in the afternoon. Other than walking around, the variety helps me.