Application of a Kinematics-Driven Approach in Human Spine Biomechanics During an Isometric Lift

Effective prevention and treatment management of spinal disorders can only be based on accurateestimation of muscle forces and spinal loads during various activities such as lifting. theinfeasibility of experimental methods to measure muscle and spinal loads has prompted the use ofbiomechanical modeling techniques. a major shortcoming in many previous and current modelsis the consideration of equilibrium conditions only at a single cross section, rather than alongthe entire length of the spine, when attempting to compute muscle forces and spinal loads. theassumption of extensor global muscles with straight rather than curved paths and of the spinalsegments as joints with no translational degrees-of-freedom, are additional issues that need to becritically evaluated when simulating lifting tasks. the kinematics-driven approach, which satisfiesequilibrium conditions in all spinal directions and levels and yields spinal postures compatible withexternal loads, muscle forces and nonlinear passive properties, while also taking into account thewrapping of trunk muscles, is employed. results demonstrate that, regardless of the methodused (optimization or emg-assisted), single-level free body diagram models yield estimationsthat grossly violate equilibrium at other levels. the computed results are also markedly leveldependent.the crucial effects of the proper consideration of global muscles with curved pathsand of spinal segments with translational degrees-of-freedom when attempting to estimate muscleforces and spinal loads in isometric lifting tasks are also demonstrated