On the characterization of interstitial fluid flow in the skeletal muscle

In this paper, we report a comprehensive experimental and theoretical approach to examine the interstitial fluid flow in skeletal muscles under external compression. The project aims to understand the transport phenomena within the three-dimensional and highly hierarchical muscular matrices, which is of physiological importance for the muscle-bone cross-talk. Gastrocnemius muscles from mouse and cow were harvested, hydrated, and subjected to indentation creep tests using a custom-designed indentation device. A theoretical model was developed considering the non-uniform compression of the muscle sample in the vertical direction. The key parameter of the theoretical model, the Darcy permeability, was obtained using a histology-structure-based theoretical approach, where an effective permeability was proposed. The theoretical model was used to predict the time-dependent interstitial pressure distribution inside the skeletal muscle. This study, providing the first quantitative estimation of the interstitial fluid pressure distribution in the skeletal muscle, is of significant importance for understanding the biophysics of the muscle-bone cross-talk, leading to new treatment strategy of musculoskeletal diseases and defects.