IFC (interferential currents) uses the transcutaneous application of alternating medium-frequency electrical currents, amplitude modulated at low frequency for therapeutic purposes. You may recall from your high school wave physics classes:
A medium frequency + an out of phase medium frequency = a low frequency interference pattern.
Medium frequency currents encounter less resistance than low frequency currents and therefore are more comfortable at the higher intensities necessary for treatment.
The electrical current is applied to the affected area using four electrodes. The four electrodes are placed in such a way that the two currents produced cross each other in the affected area. Where the two currents meet, they actually ‘interfere’ with each other; hence the name “interferential”. The electrodes will usually be used with a damp sponge placed between the electrode and the patient’s skin or a conductive gel may be used. During treatment you will feel a tingling or “pins and needles” sensation at the contact area of the sponges and may also feel the tingling sensation throughout the area being treated. This sensation may continue for a brief period following treatment as well. The intensity of the current should be increased within the patient’s comfort level. A stronger current will usually have a more beneficial effect but the intensity should not be turned up so high as to cause pain. This modality addresses the issues of pain, spasm, and inflammation. it is important that you also address other issues associated with your condition with an appropriate exercise and manual therapy program as prescribed by your physiotherapist.
The physiological effects of IFC include:
1. An increase in localized blood flow which can improve healing by reducing swelling (the additional blood flowing through the area takes edematous fluid away with it) and as a result helps remove damaged tissue and bring nutrients necessary for healing to the injured area
2. The stimulation of local nerve cells that can have a pain reducing/anaesthetic effect due to potentially blocking the transmission of the pain signals (pain gate mechanism) or by stimulating the release of pain reducing endorphins (opioid mechanism).
3. Relaxation of muscle spasms can be achieved through external application of an electrical current, overcoming some of the muscle inhibition often caused by local injury and swelling.
4. Increased permeability of the cell membrane which helps ion movement to and from cells thus promoting healing.
IFC is used to:
•Reduce muscle spasms and promote muscle relaxation
Jorge S, Parada CA, Ferreira SH, Tambeli CH. (2006) Interferential therapy produces antinociception during application in various models of inflammatory pain. Phys Ther. 2006 Jun;86(6):800-8.
Johnson MI, Tabasam G. (2003) An investigation into the analgesic effects of different frequencies of the amplitude-modulated wave of interferential current therapy on cold-induced pain in normal subjects. Arch Phys Med Rehabil. 2003 Sep;84(9):1387-94
Cheing GL, Hui-Chan CW. (2003) Analgesic effects of transcutaneous electrical nerve stimulation and interferential currents on heat pain in healthy subjects. J Rehabil Med. 2003 Jan;35(1):15-9.
Jarit GJ, Mohr KJ, Waller R, Glousman RE. (2003) The effects of interferential therapy on post-operative pain, edema, and range of motion of the knee. Clin J Sport Med. 2003 Jan;13(1):16-20.
Johnson et al. (2002) A single blind placebo controlled investigation into the analgesic effects of interferential currents on experimentally induced ischemic pain in healthy subjects. Clin Physiol & Func Im 187-196