Abstract: Functional Electrical Stimulation (FES) can be applied to a user in an assist as needed manner using a closed feedback loop based on user effort. A system can include at least one measuring device to record data indicative of a movement of at least one muscle, at least one stimulating electrode to provide an electrical signal to a muscle, and a controller to implement the closed feedback loop. The controller can instruct the user to try to perform a movement, apply the electrical signal, receive the recorded data, estimate an effort expended by the user, correct the effort expended by the user, determine if the electrical signal should be altered based on at least the user's effort, and if needed, alter the electrical signal. The controller can correct the effort based on a volitional muscle force, a stimulated muscle force, and an occlusion between the two.