Effect of Muscle Soft Tissue on Biomechanics of Lumbar Spine under Whole Body Vibration

The object of this study was to simulate effect of muscle soft tissue on resonant frequencies and configuration (deformation and displacement) of lumbar spine in vivo under whole-body vibration (WBV). The three-dimensional (3D) finite element (FE) models of human body including skin, muscle soft tissue, viscera, ligaments, lumbar intervertebral disc (LID) and skeleton were created and validated. Modal analysis was performed by FE method. Results were that muscle soft tissue increased the resonant frequencies of lumbar spine. The first vertical resonant frequency (FVRF) changed greatly with the variation of Young's modulus of muscle soft tissue in range of 0.01 MPa-0.15 MPa. Muscle soft tissue reduced the modal displacement of the lumbar spine. Especially the modal displacement in the anteroposterior direction was reduced by at least 40%. The risk injury area of lumbar was at low lumbar region under vertical WBV. The conclusions were that muscle soft tissue played a very important role in biomechanics of lumbar spine, and we could contract muscles of whole body for protection of lumbar spine under WBV with high vibration amplitude. The findings could be helpful in understanding the biomechanics of lumbar spine under WBV and offer potential references for spinal disease protection and orthopedics.