The in vitro passive elastic response of chicken pectoralis muscle to applied tensile and compressive deformation.

The mechanics of passive skeletal muscle are important in impact biomechanics, surgical simulation, and rehabilitation engineering. Existing data from porcine tissue has shown a significant tension/compression asymmetry, which is not captured by current constitutive modelling approaches using a single set of material parameters, and an adequate explanation for this effect remains elusive. In this paper, the passive elastic deformation properties of chicken pectoralis muscle are assessed for the first time, to provide deformation data on a skeletal muscle which is very different to porcine tissue. Uniaxial, quasi-static compression and tensile tests were performed on fresh chicken pectoralis muscle in the fibre and cross-fibre directions, and at 45° to the fibre direction. Results show that chicken muscle elastic behaviour is nonlinear and anisotropic. The tensile stress-stretch response is two orders of magnitude larger than in compression for all directions tested, which reflects the tension/compression asymmetry previously observed in porcine tissue. In compression the tissue is stiffest in the cross-fibre direction. However, tensile deformation applied at 45° gives the stiffest response, and this is different to previous findings relating to porcine tissue. Chicken muscle tissue is most compliant in the fibre direction for both tensile and compressive applied deformation. Generally, a small percentage of fluid exudation was observed in the compressive samples. In the future these data will be combined with microstructural analysis to assess the architectural basis for the tension/compression asymmetry now observed in two different species of skeletal muscle.