Effect of skeletal muscle immobilization in regional anisotropic viscohyperelastic properties change

Abstract

Abstract Passive mechanical properties in three different zones of biceps brachii immobilized in short position and its free contralateral were investigated. For that, in vitro equibiaxial relaxation tests were performed on samples collected skeletal muscles of immobilized rats during one or two weeks. From data obtained in two plane axes of loading, a viscohyperelastic anisotropic model described by a strain energy function coupled with second order Maxwell’s model, was used to identify the material parameters. It has been shown that the zone influences the material parameters of the hyperelasticity behaviour while the immobilization acts rather on the viscoelasticity response. The muscle atrophy caused by immobilization leads to a more linear mechanical behaviour along the axis of the muscle fibers. Furthermore, fibrosis quantified by histological analysis confirms the highly non-linear behaviour along the other axis. These structural changes also contribute to the increase in relaxation following immobilization along both axes (+ 11.7% and + 15.5% on average with p < 0.001 and p < 0.01 respectively for each axis).