In designing the chair, we used anthropometric data (average measurements of the human body), and 3D human modeling along with 3 years of multiple iterations to determine the placement of the back pads and the pivot points.
Low back pad position: It’s positioned to hit the top of the pelvis. A tall person sits farther back on the seat and the pad is in its highest position for a tall person, supporting the top of the pelvis. A shorter person sits shallower on the seat and as the low back pad comes forward, it rotates slightly downward and will hit the shorter person at the top of the pelvis.
Upper back pad: This pad is intended to simply offer gentle support since the low back pad is responsible for aligning the spine and holding it there. Although the upper back pad will make contact in a slightly different place, the user will get the needed thoracic stability and the taper allows shoulders to roll back and freedom of arm movement.
We tested our chairs on persons 4’11”- 6’8” and found that the chair supported them in an effortless upright position.