The document discusses interferential therapy (IFT), including its principles, working mechanisms, and applications. IFT involves applying two medium frequency currents simultaneously to generate low frequency interference currents in the body. Key points include: - IFT uses medium frequencies between 1000-10,000 Hz to generate low frequency currents from 50-150 Hz. This allows for deeper, more comfortable current penetration. - IFT can be applied using bipolar, static quadripolar, or vector scan quadripolar methods depending on the treatment area and desired effects. - Physiological effects include pain relief, muscle stimulation, increased blood flow, and edema reduction depending on the frequency used.

1. INTERFERENTIAL
THERAPY -
Electrodiagnosis &
Physical agents
Course Code: MPT19205
GUIDED BY : Prof. P. Kamalanathan
PRESENTED BY : BATCH – 06.
Masters Of Physiotherapy, 2nd Semester ( 1st YEAR ),
2021 BATCH, SRMIST, COLLEGE OF PHYSIOTHERAPY,
KATTANKULATHUR, TAMIL NADU.

2. INTRODUCTION
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3. Medium frequency currents : frequency falls between
1000 Hz to 10,000 Hz with therapeutic range of 50 –
150 Hz depending upon the conditions and stages of
the pathology. So the advantages of application of IFT
are :
• MF Current associated with lower skin impedance
• More comfortable than low frequency currents
• More tolerable current penetration through the skin is
possible.
It is the production of low frequency currents in the body
by the simultaneous application of two different medium
frequency currents.
INTRODUCTION
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4. SKIN IMPEDANCE
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5. PRINCIPLES
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7. PRINCIPLES OF WEB INTERFERENCE :
COMBINED EFFECTS
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8. PRINCIPLES OF WEB INTERFERENCE :
COMBINED EFFECTS
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9. PRINCIPLES OF WEB INTERFERENCE :
COMBINED EFFECTS
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10. WORKING & PRODUCTION
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11. WORKING & PRODUCTION
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12. WORKING & PRODUCTION
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13. WORKING & PRODUCTION
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14. AMPLITUE MODULATION FREQUENCY
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17. AMPLITUDE MODULATION FREQUENCY
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Vector effect
The interference field is rotated to an angle of 450 in each direction, the field
thus covers a wider area. This is useful in diffuse pathology or if the site of the
lesion cannot be accurately localized.
Frequency swings
Some equipments allows a variation in the speed of the frequency swing. A
rhythmic mode may be a continuous swing from 0 to 100 Hz in 5-10s and back
in similar time or it may hold for 1-6s at one frequency followed by 1-6s at
another frequency with a variable time to swing between the two.
Constant frequency
Some treatments may be carried out with the interference fixed at a certain
frequency. Rhythmic frequency is useful if several types of tissues are to be
treated at once. A variation in the frequency also overcomes the problem of
tissue accommodation where the response of a particular tissue decreases with
time.
TYPES OF IFT

19. APPLICATION OF
INTERFERENTIAL THERAPY

20. SKIN IMPEDANCE
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21. SKIN IMPEDANCE
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22. METHODS OF IFT APPLICATION:
• 2-poles ( Bipolar)
• 4-poles : Quadripolar static
Quadripolar with vector scan
• Stereo-dynamic method (3D)
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23. BIPOLAR METHOD:
• Description: 2 poles (Bipolar) / 1 channel / 2
electrodes
• Production: Interference of two medium frequency
sinusoidal current circuit 1; C1 = 3000HZ with another
circuit; C2 = 3050 HZ, to introduce low frequency
current with beat frequency (50HZ).
• Modulation: Amplitude and frequency modulated
beats are pre-mixed in the machine before it is
delivered in the patients skin.
• Field: static
• Shape:Oval
• Intensity: strong but comfortable, highest tolerance of
muscles contraction.
• Uses: suitable for small area ( ankle, elbow)
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25. STATIC QUADRIPOLAR
• Description: 4-poles IFC ( quadripolar) 2 channels/ 4
electrodes.
• Production: Interference of two medium frequency
sinusoidal current circuit 1 ; C1 = 3000HZ, with another
circuit; C2 = 3050HZ, to introduce low frequency current
with beat frequency (50HZ).
• Modulation: Amplitude and frequency modulated beats
are pre-mixed in the patients skin.
• Field : static
• Shape: four-leaf clover
• Intensity: strong but comfortable, highest tolerance of
muscles contraction. The maximum amplitude of current is
halfway between the lines of two currents.
• Uses: for acute conditions because of its mildness effect.
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27. QUADRIPOLAR VECTOR SCAN:
• Description: 4-poles IFC ( quadripolar) 2 channels / 4
electrodes
• Production: Interference of two medium frequency
sinusoidal current circuit 1 ; C1=3000HZ, with another
circuit; C2= 3050HZ; to introduce low frequency current
with beat frequency (50HZ)
• Modulation: Amplitude and frequency modulated
beats are pre mixed in the patients skin.
• Field: dynamic
• Shape: circular
• Intensity: strong but comfortable; highest tolerance of
muscles contraction. The maximum amplitude of
current is halfway between the lines of two currents.
• Uses: best used for large area and diffuse pain as
shoulder, back, and thigh.
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29. STEREO DYNAMIC METOD(3D):
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30. IFT APPLICATION PARAMETERS
• STIMULATOR TYPES: 1) Desk cabinet (line- powered)
2) portable (battery –powered)
• METHODS OF DELIVERY:
1) BIPOLAR: for localized
tissue
2) QUADRIPOLAR: for deeper
tissue
3) QUADRIPOLAR WITH VECTOR:
for deeper tissue with enlarged
area
• CURRENT MODES : constant current modes
sweep current ( rhythmic current modes)
• ELECTRODE TYPES: pad, rubber, carbon-impregnated.
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31. Dosage of interferential therapy
• For pain relief = 80-100 Hz
• For reduce swelling = 1-10Hz
•Reduce edema = 100 Hz
• For partial tetany contraction = 30-
100 Hz
•Apply for 15 minutes
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32. CONTD;
• INTENSITY OF CURRENT: use an intensity of current
which produces a strong but comfortable prickling
sensation without a muscular contraction.
1 ) Increase current until the patient feels a definite
prickling, and leave for 1-5 minute for it to decrease.
2) increase current again until the patient reports a slight
muscular contraction, then decrease until contraction
stops.
• DURATION OF TREATMENT:
• IFC usually applied for 10-20 minutes treatment at a
normal intensity.
• should not be given to one area for longer than 20
minutes.
• If more than one area is to be treated a total time
should not exceed 30min.
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33. CONTD;
• FREQUENCY OF TREATMENT:
In most cases, treatment every other day (i.e.3/wk)
is ideal.
A course of 12-24 treatments is given(use until IFT
is no longer effective).
ELECTRODE PLACEMENT:
1) KNEE /ELBOW PAIN:
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34. CONTD;
2) NECK/BACK PAIN:
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35. 3)SHOULDER PAIN:
CONTD;
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36. PHYSIOLOGICAL EFFECTS
The physiological effect of IFT depends upon
1. Magnitude of current
2. Type of mode used – rhythmic or constant
3. Frequency range used
4. Accuracy of electrode positioning
Different beat frequencies lead to different effects
• Higher beat frequencies ( around 100 Hz) used for
analgesic effect
• Lower beat frequencies (around 10 Hz ) used for
contraction of innervated muscles
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37. Main clinical application are:
1. Pain relief
2. Muscle stimulation
3. Increased local blood flow
4. Reduction of edema
1. PAIN RELIEF
It is the most important effect and can be achieved by several mechanism
 ACTIVATION OF PAIN GATE CONTROL MECHANISM
Large diameter afferent nerve fibers stimulate closes the gate of
nociceptive impulses in posterior horn of spinal cord
 ACTIVATION OF NOCICEPTIVE FIBERS
Nociceptive fibers activation diminish pain by descending pain
suppressor system
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38.  PHYSIOLOGICAL BLOCK
High frequency electrical stimuli above 50 Hz cause temporary
physiological block in myelinated and unmyelinated nociceptor nerve fibers
(Aẟ + C fibers)
 INCREASED BLOOD FLOW
Pain suppression due to - increased blood flow
- tissue fluid exchange
( blood flow increases it removes chemical irritants which stimulate nerve
endings)
 ABSORPTION OF EXUDATES
Exudates is accelerated by frequency of 1 – 10 Hz with rhythmical
pumping action produced by muscle contraction
Helps to absorb exudates and reduce swelling
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39.  MUSCLE CONTRACTION
Low beat frequency stimulate motor nerves ( 10 – 50Hz) causes
contraction of voluntary muscles and smooth muscles contraction
reduces oedema
2. MUSCLE STIMULATION
Stimulation of the motor nerves can be achieved with a wide range of frequencies.
Clearly, stimulation at low frequency (e.g. 1Hz) will result in a series of twitches,
whist stimulation at 50Hz will result in a tetanic contraction. patients who cannot
generate useful voluntary contraction, IFT may be beneficial. The most effective
motor nerve stimulation range with IFT lie between approximately 10 and 20, maybe
10 and 25Hz. Stimulation below 10Hz results in a series of coarse twitches which
may be of clinical benefit. Stimulation at higher frequencies that bring about a partial
tetany (usually around 20 or 25Hz) can generate a strong tetanic contraction, which
might be considered beneficial to assist patient appreciation of the required muscle
work,
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40. 3. BLOOD FLOW
Effect of blood flow is believed to be due to
- Effects of suction electrodes on tissues
- Effects of muscle stimulation on circulation
- Deep tissue penetration stimulates parasympathetic nerve
fibers for increased blood flow.
4. OEDEMA
Local muscle contraction combined with its local vascular
changes encourages the reabsorption of Tissue fluid. The use of
suction electrodes may also be beneficial .
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41. Therapeutic effects
Pain Relief – A frequency of 100HZ reduces pain effectively by
closing the gait to pain
stimulation of large diameter afferents .
e.g. Osteoarthritis , LBP , Frozen shoulder ,
rheumatic arthritis , spondylosis , neuralgia
etc.
Edema – AMF – 1- 10 HZ generally used. It activates the
musculoskeletal pump to
activate lymphatic and venous return. 100HZ cause
vasodilation to reduce edema
e.g. – edema of foot

42. Stress incontinence – Male – stress incontinence following prostatectomy
2 electrodes placed on either side of gluteal cleft,
under ischial tuberosities anterior to anus.
Female – women following multiple vaginal delivery,
Older age during coughing , One electrode
under both ischial tuberosities and one over
anterior perineum.
• Muscle injury
• Muscle stimulation – Prevents muscle wastage , re- education ,
10 – 15 Hz rhythmic, they produce stimulation
deep innervated muscle tissue.
• Ligament injury
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43. 1. Pain Relief in conditions such as causalgia,
2. herpes zoster,
3. neuralgia.
4. Cervical spondylosis.
5. Osteoarthritis of the knee.
6. Ankylosing spondylitis
7. Rheumatoid arthritis.
8. Frozen shoulder.
9. Disc herniation.
10.Spinal canal stenosis.
11.Incontinence
12.Reduction of Edema
13.Muscle injuries
14.Ligamentous injuries
INDICATIONS
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44. CONTRA-INDICATIONS
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45. PRECAUTIONS OF IFT
• IFT apparatus must be 6 meters away from the
SWD machine.
• Abnormal skin sensation.
• For patients with febrile conditions outcome of
the first treatment must be monitored.
• Patients with epilepsy, advanced cardio
vascular conditions or cardiac arrhythmias
should be treated in the direction of the
physiotherapist.
• Treatment which involves placement of
electrodes over the anterior chest wall.
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46. • This treatment is Not eligible for athletes during
their Endurance training, but it can be applicable
only after their training events get over.
• during pregnancy this therapy is generally not
given, as it may cause harm to the mother and
child both.
• this therapy is not used in any muscle regaining
strategy.
• infants or children below 12 years of age are
generally not eligible for this therapy.
ADVERSE AFFECTS OF IFT
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Interferential current therapy works by sending small amounts of electrical stimulation to
damaged tissues in the body. The therapy is meant to boost the body's natural process of
responding to pain, by increasing circulation thus produces hormones that promote healing.
IFT delivers intermittent pulses to stimulate surface nerves and block the pain signal, by
delivering continuous deep stimulation into the affected tissue. IFT relieves pain, increases
circulation, decreases edema, and stimulates the muscles. A frequency of 100Hz may
stimulate the large diameter A-beta fibers, which have an effect on the pain gate, and inhibit
the transmission of small-diameter nociceptive traffic ( C and A-delta fiber), which effectively
closes the gait to painful impulses. Interferential current Increases the circulation of blood
thus reduces swelling, by washing away the chemicals that stimulate the nociceptive nerve
endings.
The frequency between 1 and 100 Hz is used to contract the normal innervated muscles.
Different types of frequencies cause different contractions, a low frequency, causes a twitch,
frequency between 5 and 20 Hz causes a partial tetany contraction and frequency from 30 to
100 Hz causes a tetanic contraction. IFT also helps to reduce edema 100Hz frequency
promotes vasodilation, thus decreases edema. And a frequency of 10 Hz activates the
musculoskeletal pump, used to promote venous and lymphatic return causing reduction of
edema. The neurons that make the autonomic nervous system, are small and poorly
myelinated like the Aδ and C fibers of the peripheral nervous system and to stimulate the
autonomic nervous system, lower frequencies are utilized to increase the blood flow.
SUMMARY

48. THANK YOU
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