Interferential Therapy: What is IFT, electrode placement, indication, contraindication

Last updated on February 15th, 2024 at 04:04 pm

• Interferential therapy is a type of electrical stimulation used in physiotherapy.
• It uses two electrical currents that intersect and create a therapeutic frequency.
• This frequency can help reduce pain, inflammation, and muscle spasms.
• Interferential therapy can also improve circulation and promote healing.
• It is often used for conditions such as back pain, arthritis, and sports injuries.

IFT physiotherapy simply means physiotherapy treatment given through an IFT machine. the IFT stands for Interferential Therapy which uses electrical stimulation to cure musculoskeletal pain such as cervical spondylosis, low back pain, knee pain, tennis elbow pain. IFT uses two medium frequency current that interferes to produce a beat frequency.

It gives a soothing and pain-relieving effect when applied, it is typically applied for 10-20 minutes duration. In this article, we will try to understand what is interferential therapy? How it is applied and how it helps to relieve pain.

Interferential Therapy vs TENS

Interferential therapy is a very integral part treatment process in physiotherapy. It is one of the several electrotherapy modes of treatment where electric current is used for getting the desired result. The other electrotherapy modes include ultrasonic therapy, shortwave diathermy, infrared lamp therapy etc.

The therapist often uses TENS therapy to help their patients. This therapy uses low-frequency alternating or direct current that is applied continuously. However, it is important to note that TENS therapy is most effective when it stimulates the nerves near the surface of the skin and does not penetrate deeper tissues.

This is because direct current and low-frequency alternating current above 1kHz face high resistance in the outer layer of the skin. As a result, treating deeper structures can be quite painful because a large cutaneous current is required for adequate current to flow deeply.

On the other hand, an alternating current of medium to high frequency (ranging from 1kHz to 10kHz) meets little resistance and can easily penetrate the tissue¹. However, there was one problem with direct use of medium and high-frequency alternating currents. It oscillate too rapidly to directly stimulate the tissue which causes discomfort¹.

During the 1950s, a solution was discovered for the issue with medium frequency alternating current. This solution involved utilizing crossing two medium frequency current to produce Interferential current. Which reduced sensory stimulus while still stimulating motor nerves for muscle contraction and offered deeper penetration in targeted areas. Additionally, it was found to be effective for pain treatment².

What is Interferential Therapy?

As the name implies, Interferential Therapy (IFT) requires two currents that interfere with each other, producing a beat frequency. Specifically, two medium-frequency currents intersect to create IFT.

When two alternating currents with the exact same frequency and rising and falling at the exact same time, they are said to be in phase. But, when the frequency differs slightly they become out of phase as a falling segment of one wave coincides with a rising segment.

So, the waves in phase interfere constructively to produce resultant waves with amplitude greater than either of the original. And, waves out of phase interfere destructively to cancel each other out.

Let me further simplify it so that anyone can understand it and explain it with diagrams. Observe the diagram below, two medium frequency currents with slightly different frequencies interfere to produce a resulting beat frequency current. These two medium frequency current is of slightly different frequency so that when they interfere they form a constructive phase and destructive phase.

This beat frequency is termed as Interferential current and the treatment process through this current is called Interferential Therapy.

Also read: Difference between faradic and galvanic current

How to use IFT machine

IFT machine comes in two forms, one is for professional use and another is a portable one which can be used by any layperson with little training. Both have a similar design but vary in features. Professional IFT consists of a machine with a control button and a display panel from where the intensity controls the supply of current. It comes with four external wires with a colour code.

One pair (two wires) is of black colour which forms one channel and another pair is of red colour which forms the other channel. One end of the wire has a connection to the machine and another end to electrodes.

Electrodes are part of the machine that is directly connected to the treating body part. Electrodes can be made of metal or carbon rubber (nowadays vacuum electrode is gaining popularity).

To apply electrodes over the body, the electrodes are covered with a wet lint pad (a special piece of cotton cloth made for this use). Many prefer gel rather than lint pads for placing the electrodes (note: the gel is used only for rubber electrodes).

Interferential therapy electrode placement simplified

You can easily learn to use a professional IFT device. For this first locate the painful spot, it may be the knee, shoulder, low back, or anything else. Apply electrode with lint pad/ gel as applicable around the spot.  

The placement of the two channels (as described above) should be such that it crosses each other. The intersecting area should be targeting the pain spot. The following figure will describe it. This is where the term “Inter-ferential’ justifies itself. Note how two medium frequency current interferes with each other.

I have covered the IFT electrode placement for various joint pain in my Youtube videos. Here I’m sharing a video on how to use IFT for low back pain. For videos on other joint pain, please follow the links below.

• IFT pad placement for elbow joint pain.
• Electrode placement of IFT therapy for ankle joint.
• IFT placement for knee pain.

Effects of Interferential Therapy on our body

Interferential therapy helps improve blood flow by stimulating the pumping action of the muscle. Improved blood circulation helps to heal the swelling and inflammation and thereby reducing the pain. Pain also reduces after the application of the IFT machine by a mechanism called pain gait theory. Here are the bullet points of its effects:

1. Pain relief- It gives instantaneous pain relief and a soothing effect.
2. Muscle spasm relief- The continuous contraction & relaxation of muscle create a muscle pump effect thereby improving the blood circulation. Its massage effect relaxes the spasmodic muscle.
3. Wound healing: Improved blood circulation helps in soft tissue repair.
4. Swelling reduction: The muscle pump effect helps drastically in improving the swelling.
5. Muscle relaxation.    

Indication of IFT

IFT helps in the improvement of many painful conditions.

1. Back pain.
2. Neck pain like cervical spondylosis, and neck muscle spasm.
3. Knee pain like osteoarthritis of the knee.
4. Frozen shoulder, shoulder pain.  

Contraindications of interferential therapy (IFT)

These are the conditions where using IFT must be avoided.

1. Bleeding area.
2. Body part with metal implants.
3. Loss of sensation, like in paralysis case.
4. Recent fracture.  

Important FAQ related to IFT

Keep reading: Motor points of face for electrical stimulation of bell’s palsy

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Sunit. S. Ekka

Dr Sunit Sanjay Ekka is a physiotherapist in practice for the last 15 years. He has done his BPT from one of the premium Central Government physiotherapy colleges, ie, SVNIRTAR. The patient is his best teacher and whatever he gets to learn he loves to share it on his Youtube channel and blog.