Finite element analysis of mechanics of lateral transmission of force in single muscle fiber

Abstract

Most of the myofibers in long muscles of vertebrates terminate within fascicles without reaching either end of the tendon, thus force generated in myofibers has to be transmitted laterally through the extracellular matrix (ECM) to adjacent fibers; which is defined as the lateral transmission of force in skeletal muscles. The goal of this study was to determine the mechanisms of lateral transmission of force between the myofiber and ECM. In this study, a 2D finite element model of single muscle fiber was developed to study the effects of mechanical properties of the endomysium and the tapered ends of myofiber on lateral transmission of force. Results showed that most of the force generated is transmitted near the end of the myofiber through shear to the endomysium, and the force transmitted to the end of the model increases with increased stiffness of ECM. This study also demonstrated that the tapered angle of the myofiber ends can reduce the stress concentration near the myofiber end while laterally transmitting force efficiently.

The role of transmembrane proteins on force transmission in skeletal muscle

“…The model is modified from a previously developed 2D FE model of a single muscle fiber (Zhang and Gao, 2012). Skeletal muscle has been viewed as a fiber-reinforced composite (Huijing 1999), in which the mechanism of lateral transmission is usually analyzed in one structural unit (Cox et al, 1952).…”

“…Skeletal muscle has been viewed as a fiber-reinforced composite (Huijing 1999), in which the mechanism of lateral transmission is usually analyzed in one structural unit (Cox et al, 1952). The basic structural unit of muscle is a single muscle fiber (Gao et al, 2007; Gao et al, 2008b; Gao et al 2009; Zhang and Gao, 2012). In this study, the single muscle fiber is modeled as a myofiber cylinder surrounded by an ECM cylinder.…”

“…Two pathways are involved in transmitting force from muscle fibers to the tendon: the longitudinal transmission, in which force is transmitted through the myotendinous junctions; and lateral transmission, in which force is transmitted laterally from myofibers to the extracellular matrix (ECM), and then to the tendon (Street 1983; Huijing et al, 1998; Gao et al, 2008b; Zhang and Gao 2012). Lateral transmission is impaired with aging, leading to decreased specific force (force/area) of whole muscle (Zhang and Gao, 2012; Zhang and Gao, 2014).…”

“…Lateral transmission is impaired with aging, leading to decreased specific force (force/area) of whole muscle (Zhang and Gao, 2012; Zhang and Gao, 2014). The mechanisms causing the impairment are not fully understood (Zhang and Gao, 2014).…”

“…The mechanisms causing the impairment are not fully understood (Zhang and Gao, 2014). Although aging induced changes in ECM contribute to impaired lateral transmission, they do not fully explain the ∼20% reduction in specific force of aged muscle (Zhang and Gao, 2012). …”