The importance of comfort for the automotive industry is increasing. Car manufacturers use comfort to distinguish their products from their competitors. However, the development and design of a new car seat or interior is very time consuming and expensive. The introduction of computer models of human and seat could accelerate this process. This paper describes the application of the MADYMO human model for one aspect relating to comfort, i.e. vibrations. A validation of the multibody 50th percentile human model for vertical vibrations was performed based on volunteer experiments. The model response shows good correlation with the volunteer responses. Investigation of forces acting on the intervertebral discs shows that maximum loading appears in the lumbar spine and the lower thoracic spine.