I, too have back problems that prohibit me from working standing up. If I do it, I pay the price with pain. So, I use high drafting type stools at each of the mills, and a secretarial chair sitting at my desk. My shop is in the basement on a concrete floor that is very hard on me, so I have put in a rubber tile floor right over the concrete, and that helps greatly. It also allows me to sweep up the chips readily, so much so, that I have gotten into the practise of sweeping every time I work. These are 1/2 meter square tiles from Lowes, that link together with each other along the edges. I had tried some thick cushiony sponge-rubber tiles from Sears, but they are too soft to roll your chair around on, and they indented from the chair casters, so back they went. I also have a set of 1/2" thick rubber mats that I use in certain fixed locations at my woodworking bench. not perfect, though.