Effect of sitting posture and seat on biodynamic responses of internal human body simulated by finite element modeling of body-seat system

This study aimed at developing a detailed three-dimensional (3D) finite element (FE) model of the body-seat system to investigate the effect of sitting posture and seat on the biodynamic responses of internal human body under vertical white noise excitation. Three postures of human models (vertical seated body (VSB), reclined seated body (RSB), and seated body in driving posture (DSB)) and three different stiffness seats were modeled. The initial boundary condition between human body and seat for biodynamic response analysis was obtained by static analysis of the body-seat system under the action of gravity. Random response analysis was performed under white noise excitation at 0–20 Hz in the vertical direction by a modal superposition method. Principal responses of lumbar intervertebral discs (LIDs) in VSB were in the range of human body natural frequencies. The damping ratio greatly decreased the peak response values of LID. When compared with the supports of the elastic seat in VSB, those of the elastic seat in RSB increased the peak response frequencies of LID in the anterior-posterior direction and decreased them in the vertical direction, thus making them equal in both directions. Compared to RSB, DSB not only increased the peak response frequencies but also changed the peak response values. The principal response frequencies of LID in both directions increased with the increase in seat stiffness. The proposed FE model of biodynamic random response analysis is a new fundamental method for gaining insights on the responses of internal human body to vibrations and can be used to investigate the responses of the human body-seat system instead of conducting experiments to evaluate the dynamic characteristics of newly designed seats and guide the design of seats for reducing the injury risk of the lumbar spine. This study created the detailed three-dimension finite element model of body-seat system to investigate effect of sitting posture and seat on the biodynamic responses of lumbar spine under vertical white noise excitation. The conclusions were that sitting posture and seat could change the peak response frequencies of lumbar spine, and designing proper seat or changing posure could avoid or reduce the effect of certain frequency excitation on lumbar spine for protect human body health under whole body vibration. The proposed FE model of biodynamic random response analysis is a new fundamental method for gaining insights on the responses of internal