Effect of sitting posture on spine joint angles and forces

The investigation of the biomechanics of human spine in different sitting postures becomes more important as humans spend an increasing amount of time in sitting postures in daily life. The purpose of this research is to investigate the effect of different sitting postures on spinal angles and joint forces in the pain-free human body by the application of motion data capturing combined with virtual musculo-skeletal modeling. The spinal angles were measured and calculated based on the location of markers on a subject's body. Captured motion data was used to train the musculo-skeletal model for inverse dynamic analysis. The output of forward dynamic analysis is individual spinal joint force. The results show that different sitting postures cause different angle changes of pelvis, thorax and spine, as well as spinal joint forces. There are significantly greater values of spinal joint force in the postures of relaxed sitting, leaning backwards and bending forwards. The result of this work aims to contribute to the understanding of complex human spine biomechanics. It also helps advocate better sitting posture to people with different requirements and proposes design for long-term seating, including for wheelchair-bound individuals.