Regional variation in the mechanical properties of the skeletal muscle

Regional mechanics of skeletal muscle were investigated from equibiaxial testing in vitro on tissue samples. Samples were collected in three excising zones in transversal direction to the myofibers. Thus, the transverse plane stiffness, likely to be dictated by extracellular matrix collagen (ECM), was studied. For that, distal, middle, and proximal samples of healthy brachial biceps of rats have been tested. Data was used to generate the material parameters of the first order Ogden constitutive model at these different zones of skeletal muscle. In addition to having a nonlinear mechanical behavior, the analysis of the material parameters of the model showed that the stiffness value of the skeletal muscle tissue may on average have doubled depending on the collected sample location (p < 0.001). Furthermore, it was also shown that during the tests, when the storage temperature of the samples increases from 22 °C to 37 °C, the stiffness of the muscle tissue becomes more important (p < 0.05), which may be due to the rigor mortis phenomenon. Thus, these results contribute to investigating the regional change of mechanical properties of skeletal muscle, particularly those of ECM that play a major role in stiffness tissue, which is essential for the development of accurate computational models.