Pre-modulation is the process of mixing the electrical currents inside the interferentail device before it is administered to the patient.  This contrasts with the classic theory of allowing the currents to cross inside the patient. 


The Infrex Plus is a pre-modulated device.



A comparison of true and premodulated interferential currents.

Ozcan J, Ward AR, Robertson VJ.

School of Physiotherapy, La Trobe University, Victoria, Australia.


OBJECTIVE: To compare true and premodulated interferential currents (IFCs) in terms of sensory, motor, and pain thresholds; maximum electrically induced torque (MEIT); and comfort.

DESIGN: Repeated-measures design.

SETTING: Laboratory setting.

PARTICIPANTS: University student and staff volunteers.

INTERVENTIONS: Participants were exposed to 4 different conditions, chosen to evaluate 2 fundamental differences between true and premodulated IFCs. The conditions were different combinations of (1) premodulated or constant-amplitude currents applied at the skin and (2) crossed or parallel current paths.

MAIN OUTCOME MEASURES: Sensory, motor, and pain thresholds; MEIT; and subjective reports of relative discomfort were recorded for each of the 4 conditions. Motor to sensory threshold ratios were subsequently calculated to assess depth efficiency of stimulation.

RESULTS: The major findings were that crossed currents (true IFC) had no advantage over parallel currents (premodulated IFC) in terms of motor to sensory threshold ratio, MEIT, or comfort, and that premodulated currents produced higher torque values and less discomfort than constant-amplitude currents (true IFC). These results contradict the claimed superiority of true IFC.

CONCLUSIONS: The findings indicate that premodulated IFC, delivered via 2 large electrodes, may be clinically more effective than the traditional true IFC arrangement in terms of depth efficiency, torque production, and patient comfort.