Computational modeling of damage in the hierarchical microstructure of skeletal muscles

One of the skeletal muscle's exceptional properties is its high damage tolerance in terms of its high toughness, which allows the muscle to withstand cracks of millimeter length while maintaining most of its strength (Taylor et al., 2012). In skeletal muscles, damage occurs on different hierarchical levels of the microstructure. We analyze the damage behavior on hierarchy levels 3 (muscle fiber) and 4 (fascicle) on which the most common serious muscle injuries occur. Our model captures damage initiation and rupture of activated muscle fibers resulting from eccentric contractions. We consider the interaction between muscle fibers and endomysium and investigate the influence of the components titin and endomysium on the mechanical behavior in pre-damaged fascicles. Endomysium generally transmits contractile forces. Our results show that high strains in pre-damaged fiber regions are not transferred by the endomysium and, thus, adjacent undamaged fibers are well protected. Moreover, the results show titin's extraordinary stabilization properties of pre-damaged muscle fibers, so that macroscopic strains of fascicles are hardly reduced in case of strongly pre-damaged fibers and intact titin.

Automated summary

Skeletal muscle has high damage tolerance due to its high toughness, which allows it to withstand cracks while maintaining most of its strength. This study focuses on analyzing the damage behavior in muscle fibers and fascicles, where most serious muscle injuries occur. The results show that the endomysium does not transfer high strains, providing protection to adjacent undamaged fibers. Additionally, titin plays a significant role in stabilizing pre-damaged muscle fibers, resulting in minimal reduction in macroscopic strains of fascicles.