In this study, we propose to simulate the center of mass trajectory during walking using a tridimensional Extended Inverted Pendulum model. For the single support trajectory simulation, we consider a modified tridimensional inverted pendulum introducing the forward displacement of its pivot point as the center of pressure translation. The model introduces a representation of the double support center of mass trajectory using the displacement of a tridimensional single pendulum around a mobile double support pivot point. The results show that the introduction of the center of pressure and the double support pivot point translations leads to reduce the center of mass vertical excursion. Besides, the model accurately predicts the center of mass lateral displacements whatever the chosen combination of stride length and width, and walking speed.