A universal closed-loop functional electrical stimulation system comprising at least one electrode assembly adapted to deliver an electrical stimulation signal to the central nervous system, peripheral nervous system, or muscles of a user, a sensor system adapted to detect a mechanical response to a muscle stimulation signal of at least one muscle associated with a muscle group stimulated through the nervous system or proximate to the electrode assembly. An electrical stimulation device operably coupled to at least one electrode assembly and the sensor system, the electrical stimulation device including a control system to automatically receive feedback from at least one characteristic of the muscle from the detected muscle response and adjust at least one parameter of the muscle stimulation signal in real-time and in response thereto and a programmed microprocessor for controlling said electrical stimulation and receiving input from said sensor system.