Modeling muscle´s nonlinear viscoelastic dynamics

Muscle´s contractile properties are complicated by its viscoelastic properties. Failure of early viscoelastic muscle models led to Hill´s force-velocity relation embodied as the contractile element. Adopting a particular force-velocity relation to describe muscle is neither easy, nor unique [1]. Time-varying elastance based models of the left ventricle have been popular since the idea was presented in 1969 [2]. This paper investigates adoption of the time-varying elastance concept to describe the viscoelastic properties of muscle. It will be shown that a time-varying elastance must be extended to a time, length, and velocity dependent elastance. Results show how a generalized force generator description of muscle [3] may be used to realistically model muscle´s viscoelasticity.