Distribution of spinal disc pressures in the seated posture subjected to impact

A musculoskeletal model for the human spine developed by the authors is used for this study. The model takes into account the equilibrium of the vertebral bodies, the intervertebral discs and segments of the upper extremities under the influence of all major muscle and joint forces. Linear programming techniques are used to obtain the muscle load sharing and the disc pressures, based on a preselected linear criterion. The criterion is formulated as a combination of all muscles forces (F), joint forces and ligament action (R,M) with suitable weighting factors, and a minimization is sought of U = F + k1R + k2M. The model is used to study the effect of sudden forward or backward acceleration forces, such as during the impact situation, on the distribution of disc pressures in the spinal column in the unsupported seated posture.