This video shows how chair adjustments can change spine posture based on the needed work. The classic ”ergonomics chair position” is trained to recline the chair back about 20-30 degrees from vertical, and the seat pan tips back about 10-15 degrees. This is a very relaxed posture with the torso back against the chair, lumbar disc pressures are lower, the thigh-torso angle is greater than 120 degrees. Theoretically, this is the position that has worked for more than 50 years.
Work changes posture! As we get more interested in the screen, reach more for the input devices, the head begins to come forward and the spine is not longer lined up. There may be 20-30 degrees of tilt in the spine—this is about as far forward as the spine will bend—almost as though the body is bent to touch the toes. The low back does not bend any farther forward!
People can correct the chair posture by perching on the front of the chair. It is easier to get upright posture, but there is little back support from the chair, and the thighs are not fully supported. This position is easier to get better spine posture, but because more work is required, there is more difficulty to sustain the posture.
A full feature chair can support good upright postures.
Sit all the way back in the chair, sit up tall in the position to do the work, and let the seat pan “float” forward to meet the body—there may be a forward tip about 10-15 degrees.
Now the pelvis is better lined up with the top of the spine. Forward reach is easier, because the spine moves from the pelvis which is the base of the spine. Importantly, it is easier to correct the spine posture from this position.
Test the spine posture by moving the torso taller and upright.
The torso is 10-15 degrees closer to the work—it may not seem like much, but that movement is half the available range of motion for the spine and supports the spine in a better working posture