A device for an exercise machine comprising a base, forming at least one substantially flat supporting surface, at least one resistant load connected to the base, at least one seat for a user, being positioned in front of the supporting surface, connected to the base in such a way that it can move from a forward position to a back position relative to the supporting surface, the seat being connected to the resistant load for performing an exercise; the device being characterized in that it comprises at least one footplate which can be selectively connected to the base at the supporting surface by removable supporting means, at least one actuator portion connected to the supporting means being designated to generate a vibration for the footplate.