VSNU

More information on question 1

A desk chair is designed to support your body.

If your chair is too low, only your rear will be supported. That causes greater pressure there, which can lead to blood vessels and nerves being cut off. You should therefore adjust the height of your desk chair so pressure is evenly spread between your rear and legs, preventing excessive pressure on the skin. If your feet can't reach the floor, the extra weight of your unsupported lower legs will increase pressure on the rear. In effect, the weight of your lower legs will hang off your upper legs.

The images below use shading to indicate the spread of pressure between the thighs and rear. Red indicates high pressure, with yellow and green showing decreasing pressure, down to blue for low pressure. You can clearly see the greater pressure on the seat bones, which protrude from the pelvis. If the surface of the support area is greater, there’s less local pressure on the skin.


“A good spread of pressure minimises the load on the ischiums. This ensures comfort. Bearing a heavy load there for a long time feels uncomfortable, and that usually serves as a warning mechanism. The result is that people shift position, perhaps too much. This is usually an unconscious, automatic reaction.” (Staarink 2007)