When you sit, the weight on your lower back is one and a half to two times bigger than when you stand. A good chair must accommodate your body sizes and must be adjustable in the following areas:

 Height of the seat

When your feet rest comfortably on the floor, a 90 degree angle between upper and lower legs is desirable. In this position, your upper legs are virtually horizontal.

 Depth of the seat

The clearance between the front edge of the seat and the back of your knee must fit a clenched first.

 Backrest

The backrest must support the area from the upper ridge of the pelvis to the shoulder blades. The curve in the backrest must support the hollow in your lower back. An adjustable tilt is desirable.