Effect of seat configuration on the biodynamic response of the head-cervical spine during exposure to different frequencies of vertical vibration

The objective of this study is to investigate the effects of vertical vibration frequencies (4-10 Hz), back support, and cushion stiffness on the head-neck biodynamic responses based on a developed and validated finite element model of a body-seat system. Modal analysis and modal dynamics methods were employed to analyze the dynamic responses of the body-seat system under different conditions. The finite element model was used to examine the effects of various vibration frequencies (4-10 Hz), back support types (No back support (NBS) and Vertical back support (VBS)), and cushion stiffness (Elastic cushion (Soft) and Rigid cushion (Hard)) on the biodynamic responses of the head-neck. The body-seat system exhibited vertical resonance frequencies of 4.50, 6.50, 5.50, and 8.00 Hz for Soft-NBS, Soft-VBS, Hard-NBS, and Hard-VBS models, respectively, with vibration amplitude increasing near resonance. Vertical back support raised resonance frequency by 1.5-3.5 Hz and amplified head-neck vibration by 8.5-46.8% with a soft cushion, while reducing it by 14.5-55.9% with a hard cushion. Cushion hardness increased resonance frequency by 0.5-2.5 Hz and amplified head-neck vibration by 7.0-17.5% without back support, but reduced it by 7.0-33.1% with back support. Vertical back support and cushion stiffness significantly influence head-neck vibrations, especially near resonance frequencies. These findings highlight the importance of considering these factors in seat design to mitigate head-cervical injuries and enhance comfort and stability in vibration environments.