ABSTRACT
A three-dimensional dynamic Finite-Element-Model (FEM) of sitting 50-percentile man is presented. The model is based on a close representation of human anatomy with special focus on the lumbar spine and muscles. The lumbar spine model consists of a detailed representation of the discs and vertebras with six different materials (including orthotropic and viscoelastic constitutive laws), non-linear ligament models and a nonlinear contact model in the articular facets. The muscle model contains the dynamic properties of passive as well as active muscle tissue. Forces in muscles are calculated using an optimization approach. The model is completed with rigid-body models for the upper torso with neck, head and arms, the pelvis and the legs and the viscera. The model is validated starting with the disc model and ending with the whole body model by numerous static and dynamic experimental results taken from literature. It is used to evaluate the influence of muscles on whole body dynamics. Forces in the lumbar spine are calculated which are necessary to assess the potential risk of whole body vibrations (WBV) for the lumbar spine.
