One of the constraining properties of the IPMC actuators is their back-relaxation. An excited IPMC actuator, instead of holding its bent state, relaxes back towards its initial shape even when the exciting signal is a DC voltage. This behavior is reported by many authors and is usually explained with diffusion of water back, or out of the electrodes. However, a non-traditional approach to the well-known elements of the traditional viscoelastic schemes – spring and damper – results with a qualitatively new model of viscoelasticity. This mechanical analogy of viscoelastic behavior elucidates the naturalness of the back-relaxation behavior of the actuators. The model is described by a system of PDEs and gives an intuitive and accurate charge-deflection correlation with back-relaxation included. The experiments carried out with actuators of different shapes show excellent accordance with the model.