A constitutive model for active-passive transition of muscle fibers

In this paper, we examine the transition of striated muscles between active and passive states. New experimental data of a muscle performing such a transition are provided, allowing for a new model to be developed to capture this mechanical behavior. Specifically, a strain energy function is formulated using the theory of transient networks, introducing an intermediate, stress-free configuration for the active muscle fibers. Additionally, energy dissipation occurring during the unloading is accounted for by specifying a pseudo-energy function. The general three-dimensional case is specialized to uniaxial deformation for comparison with test data, from which material parameters are determined. Finally, numerical results are presented, demonstrating the model's ability to capture the mechanical behavior with changing stimulus. (C) 2011 Elsevier Ltd. All rights reserved.