Two different polarization regimes have mainly been used during electrolytic deuterium loading of palladium cathodes to produce an excess of heat in “cold fusion” experiments. Most of the experimentalists apply a constant current density, while some prefer to work with a square-wave current. The different effects of the two techniques on the deuterium dynamics through the cathode are not yet very clear. Thus, a transport model supported by a computer code is used to describe the evolution of the deuterium concentration profile inside a palladium membrane cathode for both operating conditions.