Interferential therapy (IFT) is widely used in physiotherapy. It is developed by Dr. Hans Nemec of Vienna, Austria in the early 1950s. It is very helpful in relieving pain due to muscle spasm and various other kinds of pain.
What is Interferential therapy?
Interferential therapy is a form of electrical treatment in which we used interferential current.
As the name suggests, there has to be two current that interferes with each other resulting in the production of interferential current.
Let me further explain it, when two medium frequency current interferes, they produce a beat frequency. This beat frequency is termed as Interferential current. The treatment process through this current is called as Interferential Therapy.
The beat frequency is the difference between the two medium frequency currents.It is low frequency. this frequency gives soothing and pain-relieving effect on the part where it is applied.
Principle of IFT:
The basic principle of interferential therapy (IFT) is to use the important physiological effects of low-frequency electrical stimulation of nerve without the associated painful and somewhat unpleasant side effects.
- To produce low-frequency effects at sufficient intensity and sufficient depth, the patient can experience much discomfort in the superficial tissue(i.e. in the skin).
- This is due to the impedance of the skin.
- Interferential therapy utilizes two of these medium frequency currents, passed through the tissues simultaneously, where they interfere with each other.
- This interaction gives rise to an interference current ( or beat frequency).
- Beat frequency controlled through input frequency.
- for example- one current was at 4100Hz and it’s associate current at 4000Hz, the resultant beat frequency, would be at 100Hz.
Treatment Parameters of IFT:
1)Amplitude modulated frequency( beat frequency):
- The AMF frequencies are the same as used in low-frequency treatment.
- The sensation induced by interferential current stimulation changes with different AMF setting.
- Low AMFs for example obtain a beating or tapping sensation, while higher AMFs obtain a buzzing or tingling sensation.
2) Frequency sweep:
- Frequency sweep means gradually changing frequency.
- It prevents the accommodation of nerves. because Nerves will accommodate to a constant signal.
- Frequency sweep is set in the machine automatically, using pre-set or user-set sweep range.
Types of sweep patterns-
- Triangular sweep patterns
- Rectangular sweep pattern
- Trapezoidal sweep patterns
3) 4 pole and 2 pole IFT:
- In 4 pole and 2 pole, IFT produced with 4 or 2 electrode system.
- There is no known physiological difference between the effects of IFT produced with 2 pole or 4 pole.
- The key difference is that with 4 pole applications the interference is generated in the tissues and with a 2 pole treatment, the current is ‘pre modulated’ i.e.the interference is generated within the machine unit.
4) Vector mode:
The vector system should only be selected, if the site of a lesion can not be accurately localized.
just like A patient who has a diffuse area of pathology, and the accuracy of the lesion, within the static interferential field is doubtful, the vector principle is used.
It produces a scanning movement of the interferential field so that all parts of the field are subjected to the maximum interferential effect.
Mainly two types of electrode used in IFT –
- Suction electrode
- Flat carbon rubber electrode
The suction electrode has the advantage of allowing the application to large flat areas or patients who are relatively immobile.
Flat carbon rubber electrodes may be easier to apply to the peripheral limbs, when they may be held in position by bandages or velcro straps.
6) Current intensity:
- Always turn the intensity dial to zero before beginning the treatment.
- The intensity should be slowly turned up until the patient signals that the required sensation has been reached.
- To neutralize adaptation, adjust intensity periodically.
7) Treatment duration:
Treatment time has been reported by most clinicians to be between 10- 15 minutes.
Physiological Effects of IFT:
This depend upon:
- Magnitude of current.
- Type of mode used i.e.rhythmic or constant.
- The frequency range used.
- Accuracy of electrode positioning.
Main physiological effect are-
- Pain relief
- Muscle stimulation
- Increased local blood flow
- Reduction of edema
- Effect of autonomic nervous system
1) Pain relief:
The pain gate theory and other mechanisms contribute significantly to the reduction of pain by interferential current.
A frequency of 100Hz may stimulate the large diameter A-beta fibers, which have an effect on the pain gate, that inhibit transmission of small-diameter nociceptive traffic ( C and A-delta fiber), which effectively closes the gait to painful impulses.
• Descending pain suppression –
• Increased Circulation-
Interferential current Improve the circulation of blood, reduce swelling which may wash away the chemicals that stimulate the nociceptive nerve ending
This is also one of the important factor for pain relief by IFT.
2) Stimulation of muscle:
If interferential frequency between 1 and 100 Hz is used, normal innervated muscle will be made to contract
The type of contraction depends on the frequency of stimulation-
- At low frequencies, a twitch is produced
- Between 5 and 20 Hz a partial tetany contraction
- from 30 to 100 Hz a tetanic contraction.
The little sensory stimulation can produce muscle contraction of deeply placed muscles e.g. pelvic floor muscles.
(It is claimed that when the pelvic floor muscles treated with interferential current, both the voluntary and smooth muscle fibers are stimulated. faradism can only stimulate the voluntary component.)
3) Reduction of edema:
- To promote vasodilation 100Hz frequency of IFT can used
- A frequency of 10 Hz which activates the musculoskeletal pump is used to promote venous and lymphatic return which effect is utilized for the reduction of edema.
4) Effects on the Autonomic Nervous system:
- The neurons that make the autonomic nervous system, are small and poorly myelinated like the Aδ and C fibers of the peripheral nervous system.
- The autonomic nervous system can stimulate at lower frequencies of ift.
- This effect can utilize for the increase of blood flow and control of incontinence.
- Pain- both cases of pain and referred pain.
- Muscle spasm
- Chronic ligament lesion
- Trigger point
- Stress incontinence – the contraction of pelvic floor muscle
Application of IFT:
- Firstly check the subject concerning for to the contraindications;
- →explain the treatment fully to the patient;
- →ensure that patient in a comfortable position;
- →keep the skin uncovered and examine the skin for the sensation of pain;
- →To reduce skin resistance, clean the skin over the region of electrode placement;
- → place the electrodes, secure the pad electrodes by velcro-strap/ tape;
- →the placement of electrodes differ from lesion to lesion;
- →select the appropriate treatment parameters;
- → always turn the intensity dial to zero before beginning the treatment;
- → once the treatment is started, increase the intensity until the desired result is produced.
- Arterial disease
- Skin infection
- Pregnant uterus
- Deep vein thrombosis
- Febrile condition
- Large open wounds
- Advanced cardiac disease
- Epiphyseal region in children
Dangers of IFT:
- Increased pain
- General malaise
- Dizziness/ faintness
- Migraine/ headache
- Neurological effect