Simulation of forces acting in the spine under continuous and transient whole-body vibrations by means of a biomechanical model

Investigations reveal that exposure to whole-body vibrations can induce degenerative changes in the lumbar spine. The purpose of this study was to assess the health risk on the basis of predicted forces transmitted in the spine. The forces were simulated by means of a biomechanical model, where ten rigid bodies represent the trunk (5), the neck (4), and the head (1) and one additional body imitates the vibrating seat. As stress examples, the model movements were simulated under sinusoidal and shock containing vibrations in the x- and z-direction. In the lumbar spine the resulting shear force was lower than the compressive force. The peak values of the compressive force were -834 N under the sinusoidal and -1188 N under the shock containing vibration. Assessing the health risk the predicted spine forces have to be compared with the strength of the spine regarding the age and gender of the worker and the dependence on the number of load cycles.