Chair lacks lower-back support. A chair that fails to support the lumbar (lower) region of the spine is a common cause of back discomfort; 35 percent more pressure can be placed on an unsupported lower back. The normal alignment of the spine is an S-shaped curve: an inward curve at the neck,an outward curve in the middle of the back, and an inward curve at the lower back. When a chair does not provide adequate lumbar support, the lower curve of the back flattens. As a person sits, the bottom of the hip bone contacts the chair first. The hip rotates, flattening the curve in the lower part of the back; the spinal discs stretch from the vertebrae causing back pain.