Biomechanical Effects of Different Sitting Postures and Physiologic Movements on the Lumbar Spine: A Finite Element Study

Abstract People sit frequently and perform various physiologic activities while seated. Intradiscal pressure in a static posture has been studied extensively, but research is lacking on how the pressure applied to the spine and disc changes during dynamic movements in different postures. In this study, finite element modeling (FEM) was used to investigate how pressure distribution on the lumbar spine changes when standing or during straight, slumped, and floor sitting. Three types of load modes, flexion, lateral bending, and axial rotation, were applied to the FEM. A moment of 10 N·m was applied at the cervical spine and a load of 300 N at the head. In the erect sitting and standing postures, there was no significant difference in the pressure distribution of the annulus fiber and nucleus pulposus, representing intradiscal pressure, according to the three movements. Stress increased by an average of 113% during slumped sitting and 123% while floor sitting compared with standing. The pressure on the annulus fibers and nucleus pulposus in the lumbar spine increased the most while floor sitting, when lumbar lordosis decreased the most. Maintaining a sitting position during physiologic activities that reduces lumbar lordosis effectively reduces intradiscal pressure associated with various degenerative disc diseases.