Disclosed is an implantable biomedical device that incorporates an electrical energy generator. The electrical energy generator harvests kinetic energy from voluntary motor activity of a human or animal and converts the kinetic energy to usable electrical energy which is used to power the biomedical device. In certain embodiments, the electrical energy generator includes a housing, an electrical conductor, an electromagnetically active mass, springs connecting the mass to the housing, and electrically circuitry to generate a usable source of electrical power for the biomedical device.