by Mitchell Reiff

Created on: March 30, 2007   Last Updated: April 18, 2007

Interferential Therapy: Tips for Effective Treatment

Interferential therapy, during the past ten years, has increased in popularity to the point that it is now perhaps the most widely used form of electrotherapy in the United States. First developed in Europe, where this unique form of stimulation has been utilized for numerous indications, interferential units have been marketed since the early 1950's. It seems, however, that a great deal of confusion, mystery and perhaps even misinformation still exists concerning this therapy. The purpose of this article is to shed some light on areas that may be confusing to the clinician, share information on proper treatment protocols and offer a few insights into treating patients with interferential therapy effectively and safely.

"TRUE INTERFERENTIAL" VS. "PRE-MODULATE INTERFERENTIAL"

The original concept of interferential therapy was developed by Austrian physician, Dr. Hans Nemec, approximately forty years ago. Dr. Nemec proposed that by crossing two slightly different medium frequency alternating currents within the tissue; a third frequency current of greater intensity is created in the deeper tissue. As an example, a frequency of 4000Hz interfering with another frequency of 4080Hz creates a third current of 80Hz. This is caused by the in phase and out of phase relationship of the two original currents as they alternate from positive to negative polarity. The third current, referred to as the "beat frequency" becomes the actual therapeutic frequency. One output of the unit is a constant 4000Hz while the second output frequency is adjustable from perhaps 4001Hz to as much as 4250Hz. This form of interferential therapy has become known as "true interferential frequency difference interferential".

A second method of creating the interference effect has been developed in recent years and has become known as "pre-modulated interferential". With this method, both outputs of the unit provide a carrier frequency of 4000Hz, however, each output has the ability to premodulate or burst the frequency within the unit. It is important that this unit has the capability of perfectly synchronizing these bursts in the same polarity, at the same time in order to create "premodulated interferential" . Units capable of premodulation are not necessarily premodulated interferential and may only provide premodulation for the purpose of bi-polar (two electrodes) stimulation.

When considering the relative merits of these two methods, many clinicians

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