Understanding the effect of an external stretching force on the electromechanical response of a strip of free-standing conducting polymer is crucial for developing devices (actuators) based on these polymers. This work deals with the electromechanical characterization of a free-standing polypyrrole strip submitted to different stretching forces when they are immersed in aqueous solutions with different doping ions. By plotting the electrical energy associated with the oxi-reduction process of a strip of polypyrrole film vs an external stretching force applied to the polymer strip, two lineal zones were obtained: the first with a negative slope for increasing low forces and a minimum followed by a second positive slope for higher forces. In addition, the electrical energy involved in this electrochemical process was strongly dependent on the size of the doping ions. As a consequence of this behavior, a degeneration of the electrical energy vs the external stress was measured, which would seriously limit the use of these systems as electro-chemomechanical actuators.