Interferential therapy (IFT) is a form of electrical stimulation. Two or three currents of differing frequencies are used. Each one is slightly out of phase. When they get mixed together it makes a low frequency current. By doing this, there's less resistance within the tissues so it can go deeper, and it's more comfortable for the patient. These frequencies slow down or stop pain messages at the spinal cord level.
IFT is a popular method of treatment for low back pain in the British Isles. It's used by many physical therapists (called physiotherapists) there for pain relief. The electric current is delivered to the tissues through patches or electrodes. The electrical device is a small, handheld, battery operated unit.
IFT has been in use for many years. Some recent studies on a similar form of electrical stimulation (called TENS) have brought the use of electrical stimulation under fire. The debate about the use of this treatment for low back pain hasn't been settled yet.