Your chair should be height-adjustable and set at the height that allows your thighs to be horizontal and feet flat on the floor. Look for a five-pedestal base with casters that swivels easily. Make sure you’re sitting straight with your lower back at a 90-degree angle. A vinyl or similar covering will be easier to maintain than cloth (and it’s allergen and dust-free).
The seat pan should at least one inch wider than your hips and should not touch behind the knees. It should be a high-density foam and distribute weight evenly. Continuous use of low-density foam can cause it to become permanently deformed and then it will not provide adequate cushioned support.
— Robin Stopper Renner is the owner of Nails by Robin in Mount Dora, Fla., and R.S.Innovations, LLC, maker of the Wrist-Assist (www.wrist-assist.com).