Time-Dependent Lateral Transmission of Force in Skeletal Muscle

The composite structure of skeletal muscle is composed of muscle fibers and an extracellular matrix (ECM) framework. This framework is associated with different levels of structure: (a) epimysium, that ensheaths the whole muscle; (b) perimysium, that binds a group of muscle fibers into bundles and (c) endomysium that surrounds the individual muscle fibers. The properties of ECM components and their interaction with muscle fibers determine the overall mechanical properties of the whole muscle. Previous studies have experimentally demonstrated that stress could be laterally transmitted through the ECM [1]. The ECM is thus an essential element in mechanical function of the muscle [2]. The most widely used model describing load transfer between a discontinuous fiber and matrix is the shear lag model, originally proposed by Cox [3]]. This model centers on the transfer of tensile stress between fibers by means of interfacial shear stresses and shear deformation of the matrix. In this paper, a modified shear lag model is developed to investigate the time-dependent mechanics of stress transfer between activated muscle fibers and the surrounding strained ECM.