ABSTRACT
As sitting has increased in the work-place, so has the worldwide incidence of occupational low back pain and related disability. This chapter examines the relationship between these trends and describes a promising intervention: continuous passive lumbar motion. In unsupported seating the pelvis tends to rock posteriorly; this causes the lumbar spine to move into kyphosis, and the centre of gravity of the upper trunk to shift anterior to the lumbar spine. Many seating studies have focused on physiologic issues, spine shape, muscle fatigue, intra-discal pressure, and determination of optimal seated postures. Seating comfort and body posture are greatly affected by chair contouring, padding, and the mechanical motions of the backrest and seat pan. Chaffin and Andersson commented that the two most important considerations in seating are adequate back support and allowance for movement or postural change. Seating should support a relaxed position yet allow freedom of motion at all times. It is generally agreed that seating should promote movement while the body is being supported in different postures.
