Interferential Therapy

Interferential Therapy


Interferential Therapy, often known as IFT, is one of the electrotherapy techniques used to treat pain. The goal of interferential therapy is to interfere with two medium-frequency currents with marginally differing frequencies. For instance, if Circuit A carries a current with a frequency of 4000 Hz and Circuit B carries a current with a frequency of 3980 Hz, the resultant low frequency will be 20 Hz, and this frequency is highly helpful in modulating pain.The difference in frequencies between the two medium-frequency currents that are created in the tissues at the place where the two currents cross is equal to a new low-frequency current known as the beat frequency.

It mostly treats chronic, post-traumatic, and post-surgical pains. The fundamental idea entails the use of low frequencies (250 pps) without causing any uncomfortable or severe side effects. IFT’s primary benefit is that it causes effects in the tissue precisely where they are needed without needless or uncomfortable skin stimulation. This method is frequently employed to trigger muscular contraction, encourage healing, and lessen edema


Vector effect

The interference field is expanded by rotating it at an angle of 450 degrees in both directions. This is helpful when the lesion cannot be precisely targeted or when there is diffuse pathology.

Frequency swings

The frequency swing’s speed might vary depending on the piece of equipment. A rhythmic mode may hold for 1-6s at one frequency followed by 1-6s at another frequency with a variable duration to swing between the two, or it may be a continuous swing from 0 to 100 Hz in 5-10s and back in a similar time.

Constant frequency

The interference may be fixed at a specific frequency during some treatments. When treating multiple tissue types at once, rhythmic frequency is helpful. A change in frequency also solves the issue of tissue accommodation, when a particular tissue’s reaction degrades over time.

Frequency sweep

The machine is programmed to automatically change the stimulation frequency, and either pre-set or user-set sweep ranges are used. The sweep range ought to be suitable for the anticipated physiological outcomes.

The patient’s level of stimulation is significantly influenced by the sweep’s pattern. Most devices provide a variety of sweep patterns:

  • Triangular sweep pattern.
  • Rectangular Sweep Pattern.
  • Trapezoidal Sweep Pattern.


The machine progressively switches from the base to the top frequency for 6 seconds when performing the “triangular” sweep pattern. While some machines include settings for 1 or 3 seconds. Between the base and top frequencies, equal amounts of each frequency are given.

The base and top frequencies are adjusted for the different stimulation pattern known as rectangular sweep, however instead of gradually switching from one to the other, the machine then “switches” between these two particular frequencies.

Between the predetermined frequency levels, one will supply the whole spectrum of stimulation frequencies, while the other will alternate between them. These two concepts are essentially combined in the “trapezoidal” sweep.


Little electrical stimulation doses are applied to the body’s injured tissues as part of the interferential current therapy process. By improving circulation and so creating hormones that aid in healing, the therapy aims to enhance the body’s normal response to pain. IFT continuously stimulates the damaged tissue at a deep level while sometimes stimulating surface nerves to inhibit pain signals.IFT stimulates the muscles, improves circulation, reduces edema, and relieves pain. By inhibiting the transmission of small-diameter nociceptive traffic (C and A-delta fiber), which effectively closes the gait to painful signals, a frequency of 100 Hz may stimulate the large diameter A-beta fibers, which influence the pain gate. By removing the substances that trigger the nociceptive nerve terminals, interferential current increases blood circulation, which reduces swelling.

The usual innervated muscles are contracted at a frequency of between 1 and 100 Hz. A twitch is caused by low frequencies, a partial tetany contraction is caused by frequencies between 5 and 20 Hz, and a tetanic contraction is caused by frequencies between 30 and 100 Hz. IFT also aids in edema reduction. Vasodilation is promoted by the 100Hz frequency, which reduces edoema.A frequency of 10 Hz also activates the musculoskeletal pump, which is utilized to encourage lymphatic and venous return and reduce edema. In order to stimulate the autonomic nervous system, lower frequencies are used to promote blood flow. The neurons that make up the autonomic nervous system are tiny and poorly myelinated, similar to the A and C fibers of the peripheral nervous system.


The effect of IFT depends upon:

  • Frequency
  • Intensity of current
  • Electrode placement


100-150 Hz constant or 90-100Hz rhythmic:These frequencies are helpful for pain management because IFT blocks tiny pain fibres by acting on big myelinated fibres in the dorsal horn. The mid-endogenous brain’s opiates, which block pain, are activated by the higher frequencies.

0-10Hz rhythmic or 10- 50Hz rhythmic : These frequencies are helpful for stimulating muscles. They cause minimal sensory stimulation while stimulating deep, typically innervated muscular tissue. The contraction transforms from a twitch to a tetanic one as the frequency rises.

0-100Hz rhythmic: The frequency range causes vasodilation. This causes the vessel walls to contract and relax, producing a sinusoidal effect.

Intensity of current 

The intensity of the current is gradually increased to the point of stimulating the muscles after the patient experiences tingling. The treatment lasts 10 to 20 minutes, depending on the individual.

Electrode placement

The skin is prepped for the procedure while the patient is positioned comfortably. The skin is washed, and petroleum jelly is applied to any skin lesions to protect them. At the treatment location, vacuum electrodes or pad electrodes are precisely positioned, and the two electrode pairs are positioned so that the crossing point of the two currents is over or inside the lesion.


IFT differs from other stimulation methods in that it uses interferential stimulation. The primary clinical uses of IFT seem to be in the following areas:

  • Pain Relief in conditions such as causalgia, herpes zoster, and neuralgia.
  • Cervical spondylosis.
  • Osteoarthritis of the knee.
  • Ankylosing spondylitis
  • Rheumatoid arthritis.
  • Frozen shoulder.
  • Disc herniation.
  • Spinal canal stenosis.
  • Muscle Stimulation – prevent muscle wastage, re-education, maintain range of motionStress incontinence
  • Reduction of Edema (Condition involving the excess collection of watery fluid in the cavities or tissues)
  • Muscle injuries
  • Ligamentous injuries


Although interferential therapy is frequently utilized, the physiotherapist should be able to use it according to the patient’s condition. Low frequency (250 pps) electrical stimulation of the nerves has considerable physiological effects that are used in interferential therapy.

Effects of Interferential Therapy:

  • Reduces pain and inflammation.
  • Increases blood circulation.
  • Causes vasodilation.
  • Removes waste substances from the affected area.
  • Increases metabolic rate.
  • Decreases blood pressure.
  • Treats chronic ligamentous lesions.
  • Cures edema and hematoma.
  • Improves restricted movements of joints.
  • Increases muscle stimulation.
  • Restores the lost movement of muscles.


IFT is a popular pain-relieving technique that doesn’t have the negative side effects that oral painkillers and anti-inflammatory drugs have. Like any other therapy approach, it has various drawbacks, including:

  • Infective condition
  • Malignancy.
  • Pacemakers.
  • Loss of sensation.
  • Danger of Hemorrhage
  • Large open wounds.
  • Dermatological Conditions.
  • Pregnant Uterus.
  • Arterial disease.
  • Febrile condition.
  • Deep vein thrombosis.
  • During menstruation.
  • Unreliable patient.
  • Fewer.

GALAXY Hospital – Medicine & Critical Care (ICU) I Orthopedics I Physiotherapy” is a 10 bedded hospital in the Heart of Bopal, Ahmedabad, which is dedicated to provide highest level of services in the fields of Internal Medicine & Critical Care, Orthopedics & Physiotherapy.