Clarification of micro damage mechanism of skeletal muscle tissue and formulation of a constitutive model of muscle taking into account the damage

点击翻译按钮获取中文摘要

From the viewpoint of injury prevention, it is very important to clarify and predict the criteria of micro damage and the mechanism of the decrease of the biological function and strength by the evolution of the micro damage. The motivations of this study are to construct a framework of a mechanical model which takes into account the micro damage of skeletal muscle.Firstly, we evaluated the relationship between the micro damage of muscular tissue and the change of its mechanical functions on strain injury and muscle contusion to clarify the influence of the micro damage on the mechanical properties of skeletal muscle. We also discussed the dependences of the activity of muscle and strain rate of the mechanical properties of muscle fascicle.To examine a framework of a mechanical model considering micro damage evolution of biological tissue, we constructed a constitutive model of cortical bone, which has relatively simple mechanical propeties. The developed model takes account of the strain rate dependency of the elastic modulus, anisotropies of the deformation and strengths, asymmetries of the deformation and strengths for tension, compression and shear, and the fracture caused by the accumulation of the micro damage.A mechanical model considering the difference of fatigability of motor unit was also studied. The proposed model represented a macroscopic fatigability of skeletal muscle qualitatively.We formulated a mechanical model of skeletal muscle and compared the simulation results with the corresponding experimental results of tensile and injury experiments of muscle. We adopted the framework of damage mechanics into the viscoelastic model for biological tissue proposed by Holzapfel et al. In this model, we assumed that skeletal muscle is a transverse isotropic viscoelastic material, and the micro damage also evolves tranverse isotropically. It was confirmed that the proposed model described the characteristic features of strain injury well.