http://www.ergonomics.com.au/how-to-sit-at-a-computer/ Push your hips as far back as they can go in the chair. Adjust the seat height so your feet are flat on the floor and your knees equal to, or slightly lower than, your hips. Adjust the back of the chair to a 100°-110° reclined angle. Make sure your upper and lower back are supported. Use inflatable cushions or small pillows if necessary. If you have an active back mechanism on your chair, use it to make frequent position changes. Adjust the armrests (if fitted) so that your shoulders are relaxed. If your armrests are in the way, remove them