Interferential therapy

Interferential Therapy or (IFT) is a type of electrotherapy treatment that uses electric currents to stimulate tissue which provides pain relief, reduction of swelling and many other health benefits.

IFT uses a range of frequencies that stimulate the body to get positive reactions such as increasing the blood supply in an area which in turn increases the healing speed.

So how does it do that?

Interferential therapy employs medium frequency currents used in 2 or 4-pole configurations to produce a low-frequency stimulation effect.
Prior to the introduction of interferential therapy in the mid-1950s, low-frequency stimulation was used for pain relief, muscle re-education, etc.
These currents, however, have the disadvantage that normal human skin has a relatively high impedance at such frequencies. In order to overcome the skin impedance, a larger voltage has to be used to achieve the desired current, resulting in a more uncomfortable treatment for the patient. In addition, the penetration depth of these currents is poor and in part is limited by the discomfort to the patient.

Interferential therapy overcomes the problem of skin impedance. At 50 Hz (faradic current) the impedance for a 100 cm2 of skin is approximately 3000 ohms. At 4000 Hz (medium-frequency) the skin impedance of the same area is around 50 ohms. This means that a much lower voltage signal can be used to produce the desired current, resulting in less skin sensation and more comfortable treatment. This medium frequency is, however, well outside of the normal biological frequency range (0.1 to 250 Hz). In order to produce the required stimulation, two medium frequencies are used. A constant frequency of, say, 4000 Hz is applied to one pair of electrodes and a slightly different frequency of say 3900 Hz is applied to the other pair. These two frequencies ‘interfere’ to produce an amplitude modulated medium frequency (beat frequency) in the tissue. The tissue responds to the cyclic rise and fall in the current intensity. It is the amplitude modulation frequency (AMF) that is within the normal biological frequency range and not the medium frequency (carrier).

More on Tim Watson’s website www.electrotherapy.org