Computation of Trunk Muscle Forces and Internal Spinal Loads in Standing Postures

The kinetic redundancy in human musculoskeletal trunk system allows for the active control of posture during a specific task while satisfying equilibrium and stability requirements. Such control could aim, for example, to minimise forces in active musculature and stresses in passive tissues. It results in a superfluous system of equations the solution of which not yet satisfactorily achieved despite its importance in evaluation and treatment of spinal disorders. Due to shortcomings in existing reduction, optimisation and EMG-driven models, and combination thereof, a novel kinematics-based finite element approach [1,2] is employed that fully accounts for the synergy between passive and active trunk sub-systems. In this study, the kinematics-based model is applied to determine spinal muscle forces and internal ligamentous passive loads at different disc levels in standing postures under gravity loads with and without 200N weights carried in both hands (positioned symmetrically close to the body, either anteriorly or on sides).