Effect of Skeletal Muscle Immobilization on Regional Anisotropic Viscohyperelastic Properties Change in a Rat Model

This study investigated the regional effects of skeletal muscle immobilization on anisotropic viscohyperelastic behavior using an in vitro rat model. Equibiaxial relaxation tests were performed on distal, medial, and proximal regions of immobilized biceps brachii samples to quantify regional differences in stiffness and relaxation. The results showed that immobilization primarily affected viscoelastic parameters—leading to increased relaxation coefficients—while the excising zone determined hyperelastic stiffness. Histological analysis revealed significant atrophy and fibrosis characterized by increased perimysium and endomysium collagen fractions. These mechanical and structural correlations suggest that immobilization-induced remodeling alters muscle anisotropy and viscoelasticity, with implications for spastic myopathy and rehabilitation research.