A system that activates a muscle to produce a functional movement in a subject through electrical stimulation is described. During operation, the system first obtains a non-isometric model which defines a functional movement associated with the muscle in response to electrical stimulation of the muscle. Next, the system uses the non-isometric model to compute an electrical stimulation which produces a desired functional movement in the subject. The system then applies the computed electrical stimulation to the muscle to produce the desired functional movement in the subject.