Tendon’s viscoelastic behaviors are important to the tissue mechanical function and cellular mechanobiology. When loaded in longitudinal tension, tendons often have a large Poisson’s ratio ($\nu >2$) that exceeds the limit of incompressibility for isotropic material ($\nu =0.5$), indicating that tendon experiences volume loss, inducing poroelastic fluid exudation in the transverse direction. Therefore, transverse poroelasticity is an important contributor to tendon material behavior. Tendon hydraulic permeability which is required to evaluate the fluid flow contribution to viscoelasticity, is mostly unavailable, and where available, varies by several orders of magnitude. In this manuscript, we quantified the transverse poroelastic material parameters of rat tail tendon fascicles by conducting transverse osmotic loading experiments, in both tension and compression. We used a multi-start optimization method to evaluate the parameters using biphasic finite element modeling. Our tendon samples had a transverse hydraulic permeability of ${10}^{-4}$ to ${10}^{-5}$ mm⁴. (Ns)⁻¹ and showed a significant tension–compression nonlinearity in the transverse direction. Further, using these results, we predict hydraulic permeability during longitudinal (fiber-aligned) tensile loading, and the spatial distribution of fluid flow during osmotic loading. These results reveal novel aspects of tendon mechanics and can be used to study the physiomechanical response of tendon in response to mechanical loading.

肌腱的粘弹性行为对组织力学功能和细胞力学生物学很重要。当承受纵向张力时，肌腱通常具有很大的泊松比（$\nu >2$) 超过各向同性材料的不可压缩性极限 ($\nu =0.5$)，表明肌腱经历体积损失，导致横向多孔弹性流体渗出。因此，横向多孔弹性是肌腱材料行为的重要贡献者。评估流体流动对粘弹性的贡献所需的腱水力渗透率通常不可用，并且在可用的情况下，会发生几个数量级的变化。在这份手稿中，我们通过在拉伸和压缩中进行横向渗透加载实验来量化鼠尾肌腱束的横向多孔弹性材料参数。我们使用多开始优化方法来评估使用双相有限元建模的参数。我们的肌腱样品的横向透水率为${10}^{——4}$ 到 ${10}^{——5}$毫米⁴。(Ns) ^-1并在横向上表现出显着的拉压非线性。此外，使用这些结果，我们预测了纵向（纤维排列）拉伸载荷期间的水力渗透率，以及渗透载荷期间流体流动的空间分布。这些结果揭示了肌腱力学的新方面，可用于研究肌腱对机械载荷的物理力学响应。