A neuromodulation system and method of providing therapy to a patient. Electrical energy is delivered to the patient in accordance with a modulation parameter, thereby providing therapy to the patient, and the modulation parameter of the delivered electrical energy is varied over a period of time, such that the delivered electrical energy is continually maintained at a sub-threshold level throughout the period of time. The sub-threshold level may be referred to as a patient-perception threshold, which may be referred to as a boundary below which a patient does not sense delivery of the electrical energy. For example, in a spinal cord modulation system, the patient-perception threshold may be a boundary below which a patient does not experience paresthesia.
