Sitting on a piano bench is not the same as sitting on a regular bench. While people sit on a regular chair, they tend to sit at the very back of the bench so that they can get the most support from the chair. However, this is not how you should sit on a piano bench. Rather, you should sit in the middle of the bench. This is because sitting far back can cause you to stretch too much while you are trying to reach the piano keys. So, the position you place the chair relative to the piano also plays a major role in the overall ergonomics.