On the characterization of interstitial fluid flow in the skeletal muscle endomysium

In this paper, the interstitial fluid flow in skeletal muscle endomysium was examined using an in-situ indentation testing in combination with theoretical modelling. The objective was to understand the transport properties of the three-dimensional and highly hierarchical muscular interstitial matrices, which play important roles in muscle-bone cross-talk and signaling during musculoskeletal development and maintenance. Gastrocnemius muscles from four 3-month old calves were harvested and subjected to a creeping test using a custom-designed device. The experiments, in combination with an anatomy-based theoretical model, were used to capture the spatial-temporal response of the skeletal muscle to external impacts. For the first time, the detailed load-induced interstitial fluid pressurization in the muscle endomyseal space was obtained. The relative contribution from the solid muscle fibers and the interstitial fluid to the temporal loading response was captured. The paper presented herein provides important information regarding the mechanical environment within the muscle tissue, which could help the future study of muscle's response to forces and its subsequent signaling to surrounding tissues in vivo.