We will sit in a chair every day to work and rest, but you will really “sit” chair? The tilt angle of the chair and the lumbar support when sitting down, the “arrow” below represents the change in the size of the pressure within the lumbar intervertebral disc. The left side of the red line (A, B) indicates that when the backrest is 90 °, the disc pressure is the largest, and in the same angle, give the lumbar increased support (such as lumbar cushion or backrest), the disc pressure will be reduced. And after the red line (C, D, E) indicates that when the backrest is tilted backward more than 90° less than 110° angle in the absence of support, the intravertebral disc pressure will be further reduced. And when the lumbar support is given at this angle can further reduce the internal disc pressure (D), but if the support is put into the thoracic spine, as described above, the body is bent over with the chest, the internal disc pressure will increase. In summary, when we are seated you should choose the seat backrest inclination in the range of 95-105 °, while giving back support, so that you can “sit”. This is especially important for drivers with a history of disc herniation or long-term driving friends. The impact of chair backrest angle and support on the lumbar spine load when sitting