hkm

2. o INTRODUCTION
o DEFINITION
o PRODUCTION
o TYPES
o PARAMETERS
o TREATMENT TECHNIQUES/PROCEDURE
o POSITION/TYPES OF ELECTRODES
o THERAPEUTIC EFFECTS
o PHYSIOLOGICAL EFFECTS
o INDICATIONS/CONTRAINDICATIONS
o DANGERS
o RECENT RESEARCHES AND REFERENCES

3. Interferential therapy utilises two of the medium frequency currents, passed through
the tissues simultaneously, where they are set up so that their paths cross & they
literally interfere with each other. This interference gives rise to an interference
(beat frequency) which has the characteristics of low frequency stimulation
As stated earlier, the principle of interferential current therapy is that when two
medium frequency of alternating currents of slightly different frequencies are
passed through the tissues.
At the same time, they interfere with one another to produce a low frequency current
effect at the point of intersection.
The resultant amplitude of this new current is the sum of the individual current
amplitudes at any given point. Thus when two peaks of amplitude in the same
direction coincide, the resultant amplitude is at the maximum (summation of
current as at A and C).
When the two peaks are in the opposite directions, there will be no current
(cancellation effect as at B). This submission and cancellation of current values
produces the amplitude-modulated beats that are characteristic of interferential
current. providing the amplitudes of the two currents are the same, the resultant
carrying frequency will be the average of the two individual frequencies. If the
frequency of the first current is 4000 Hz and the second is 4100 Hz, the resultant
current frequency is 4050 Hz 4000-4100 .
2

4. This resultant current varies in amplitude i.e. it is amplitude modulated. The frequency
with which the amplitude varies is called the Amplitude Modulated Frequency or
Beat Frequency or the Treatment Frequency and is equal to the difference in
frequencies between the two interfering currents in the above instance, 100 Hz. It is
this beat effect that acts like any other low frequency current and stimulates nerves
and muscles.

5. DEFINITION
Application of two medium frequency currents produces low frequency current effect
at the point of intersection of the two currents. This is the basic principle of IFT.
Interferential current therapy is the application of electrical energy through the
tissues in which two medium frequency alternating currents of around 4000 Hz,
slightly out of phase, produce an amplitude modulated current of low frequency
through the effect of interference.
Principle of interference using two
channels of medium frequency
currents

6.  Interferential current is the resultant current produced when two or
more alternating currents are applied simultaneously at the point of
intersection in a given medium.
 Impedance: resistance, capacitance and inductance all these
collectively form the IMPEDANCE of the circuit.
 This impedance is a type of resistance produced by the tissues against
any electrical stimulation of low frequency.

7. •one of the currents is kept in constant of 4000 Hz and other can be varied between
3900 and 4000 Hz
•An interference effect at a “Beat frequency” is equal to difference in frequency
between the two currents. It is produce in the tissue at the point where the two
current cross .
FOR EXAMPLE,
•CIRCUIT(A) - 4000 Hz
•CIRCUIT(B) - 3900 Hz
•BEAT FREQUENCY -100 Hz
Where,
•Circuit A and B are medium frequency
•Beat frequency produced is a “Low Frequency”

8.  It is the resultant frequency produced by the two medium frequency currents
they interfere, which is the difference of the frequency between the two
medium frequency currents.
 By varying, the frequency of second circuit relative to the constant frequency of
the first. It is possible to produce a range of beat frequencies deep in the
patient tissues.
For Example,
 If circuit A carries a current with a frequency of 4000 Hz and circuit B one of
3980 Hz, then the beat frequency will be 20 Hz.
PRODUCTION OF WAVES
There are 3 types namely,
Constructive
Destructive
continuous

9. Constructive interference :
 When the two sinusoidal waves that are exactly in phase or one ,two or three
wavelength out of phase , the waves supplement each other in constructive
interference.
Destructive interference :
 When the two waves are different by 1/2 a wavelength (of any multiple)the
result is cancellation of both waves .
Continuous Interference :
 When the two waves are slightly out of phase collide and form a single wave
with progressively increasing and decreasing amplitude

10.  Interference occurs between two unmodulated currents, crossing each other’s
path within the target tissue.
 In this classical form of interference current, modulation depth is 0 per cent at
the axis of two electrodes of pole. In this direction no stimulation takes place.
 100 per cent modulation takes place only at a diagonal, creating a field of
stimulation perpendicular to the lines of forces between two electrodes of a
single pole.
 Since the lines of forces of two poles are crossed within the tissues, a four
armed (chatuevuj) field is generated. This type of pattern is called the Clover
Leaf Pattern (Fig. 01)
 The effect of this type of field produced by four pole application is very
dependant on the direction of electrode placement and the resultant field.
 It is vital to position the crossing area of the currents at the correct location to
ensure the accurate alignment of the field of 100 per cent stimulation, with the
target tissue.
 Since the stimulation is optimal only in two directions, the position of the four
electrodes must be done with great care.
 Fine tuning of the spread of stimulation can be done with the balance control.
It works like the balance knob of a sound system.

11. Fig. 01: Clover leaf pattern of electrical
field in IFT
Fig. 02:Isoplaner
vector field application to the knee joint
The Clover Leaf Pattern
Isoplaner Vector Field
• Applied through four electrodes like classical
interference current (Fig. 02).
• Gives a stimulus, which is equal in all directions
instead of clover leaf pattern.
• The depth of modulation is 100 per cent and the
current is same in all directions, making sure that all
tissue between the four electrodes will receive effective
treatment.
• Suitable for large joints like the knee, particularly when
swollen and when the complaint is diffuse and hard to
localize.
• Because of the mildness of isoplaner field stimulation,
it is best suited for acute conditions like sciatica (Fig.
03).
Fig. 03: Placement of
electrodes
for application
of IFT to the sciatic root

12. Dipole Vector Field
• Though applied through four electrodes, the distribution of current in
one direction is 100 per cent and the other is 0 per cent.
• This enables the current to be applied selectively to a specific area
through static vector mode or rotate the field like the lights of a
lighthouse, stimulating tissues cyclically in all directions between the
four electrodes, in a dynamic vector mode.
• The static vector mode is most useful in case of longitudinal structures,
e.g. Brachioradialis or rectus femoris muscles. A band of maximum
intensity may be set up between the poles of the electrodes to target a
specific structure along its entire length, avoiding unnecessary
stimulation of adjacent structures.
• The dynamic vector has deionising effect on acute muscle spasm of
large muscular areas because of the massaging effect it creates and its
soothing nature of stimulation.
• Cyclic contraction and relaxation creates pumping in muscles,
increasing venous drainage, reducing oedema, and improving blood
circulation.
 This type of current is most suitable for the treatment of muscle spasm
of heavily muscled areas like painful shoulder, low back pain and, pain
of the thighs etc

13.  This type of current gives the same type of stimulation as compared to
four pole interferential method
 Current modulation depth is 100 percent in all direction. Maximum
stimulation is produced in the tissues lying between the electrodes,
along the lines of forces connecting the electrodes and 0 per cent
perpendicular to the lines of forces.
 Application is simpler due to less number of electrodes, though in
depth effect is comparable to the four-pole method.
 Suitable for localized smaller areas like the temporomandibular joints,
muscles of the hand, paracervical muscles, etc. It is specifically used to
achieve relief of pain in sciatic neuralgia.

14. Most modern IFT units (Figs 04 and 05) allow the therapist to get tailor made current, suitable to
treat a specific disorder, which may be built in to the memory of the software based equipments
or by adjustment of following machine parameters:
 Amplitude modulation parameter (AMF), to choose the basic value of the low frequency
modulation that is desired.
 Spectrum parameter, to set the range of variation in the AMF value that is desired; setting the
AMF at 100 Hz and spectrum at 50 Hz will give an AMF variation from 100 Hz upto150 Hz and back
to 100 Hz. The spectrum is useful in preventing accommodation in nerves (Fig.06).
For example: AMF at 100Hz and spectrum at 50Hz will give an AMF variation from 100Hz up to 150Hz
and back to 100Hz.
Interferential therapy makes use of the principle horse Bernard bye by varying the frequency to
prevent accommodation
It denotes the range of frequency during the treatment
In this range, all frequencies are automatically transverse
 Sweep time parameter sets the time period for he AMF to change from base to peak frequency.
Faster the sweep less painful is the stimulation. However, if strong muscle contraction or sensory
input is desired, then the sweep must be slow, to ensure aggressive stimulation.
 Balance, elective current applied through the skin depends on the condition of electrode, sponge
and the skin.
Hence, two currents are applied they are may the unequal current passing through each circuit
This occurs due to the unequal resistance encountered
In order to compensate this situation the current in both the channels can be equalised
 Sweep, It is possible to change the frequency between preset one and Preset one plus additional
frequency continuously in prefix pattern and time is the sweep

15. Fig. 04: Advanced Interferential equipment Fig. 05: Overall arrangement of the interferential
therapy instrumentation (equipment and electrodes)
in a clinical setting
Fig. 06: Advanced interferential equipment

18. •For pain relief = 80 – 100 Hz
•For reduce swelling = 1 – 10 Hz
•Reduce oedema = 100 Hz
•For partial tetany contraction = 5 – 20 Hz
•For tetany contraction = 30 – 100 Hz

19.  Electrical stimulation for pain relief has widespread clinical use.
 Direct research evidence for the use of IFT in pain relief is
limited.
 One could use the higher frequencies (90-150 Hz) to stimulate
the pain gate mechanisms and thereby mask the pain symptoms
for the duration of application.
 Alternatively, stimulation with lower frequencies (1-5 Hz) can be
used to activate the release of indigenous opiates, providing
long-term relief of pain.
 These two different modes of action can be explained
physiologically. Each has different latent periods and varying
duration of effect.
 Relief of pain may be achieved by stimulation of the reticular
formation at frequencies of 10 to 25 Hz or by blocking C fibre
transmission at frequencies greater than 50 Hz.

20.  Stimulation of the motor nerves can be achieved with a wide range of
frequencies.
 Stimulation at low frequency (e.g. 1 Hz) will result in a series of
twitches:
 Stimulation at 50 Hz will result in a titanic contraction.
 The choice of treatment parameters will depend on the desired effect.
 To combine muscle stimulation with an increase in blood flow and a
possible reduction in oedema, selecting a frequency range which does
not produce strong sustained titanic muscle contraction.
 In such cases, a sweep of 10 to 25 Hz is often used, to produce pumping
effect on the target muscles, which will help in drainage of fluid from
the interstitial space.
 There is no primary nervous control of oedema re-absorption and the
direct electrical stimulation of blood flow is limited in its effectiveness.
 It is suggested therefore, that in order to achieve these effects, suitable
combinations of muscle stimulation should be made.

21.  The stimulation was applied via suction electrodes, and the outcome could
therefore be as a result of the suction rather than the stimulation, though this
is largely negated by virtue of the fact that other stimulation frequencies were
also delivered with the suction electrodes without the blood flow changes. The
most likely mechanism is via muscle stimulation effects (IFT causing muscle
contraction which brings about a local metabolic and thus vascular change).
The possibility that the IFT is acting as an inhibitor or sympathetic activity
remains a theoretical possibility rather than an established mechanism.
 Based on current available evidence, the most likely option for IFT use as a
means to increase local blood flow remains via the muscle stimulation mode,
and thus the 10-20 or 10-25Hz frequency sweep options appears to be the most
likely beneficial option.

22. IFT has been claimed to be effective as a treatment to promote the
reabsorption of oedema in the
tissues..The preferable clinical option in the light of the available
evidence is to use the IFT to bring about local muscle contraction(s)
which combined with the local vascular changes that will result
could be effective in encouraging the reabsorption of tissue fluid.
The use of suction electrodes may be beneficial.
If IFT has a capacity to influence oedema, the current
evidence and physiological knowledge would suggest that a
combination of pain relief (allowing
more movement), muscle stimulation (above) and enhanced local
blood flow (above) is the most likely combination to be most
effective.

23.  Preparation of the patient and the machine is done, as before any low
frequency electrical stimulation
 The same local precautions, general contraindications, environment and
the safety considerations apply for IFT, as in case of low frequency
stimulation.
 The IFT is usually applied through four carbon rubber electrode plates
between 5 and 15 sqcm in size. These are applied on the prepared skin,
with a coating of conductive electrode gel and fixed with elastic strap.
 Some IFT machines have built-in or optional vacuum suction pumps, for
application of vacuum cup electrodes, with moist sponge fillers to
maintain electrical contact with the skin. Fixing such electrodes is easy,
particularly over odd-shaped areas like the shoulder joint.
 Electrode positioning should ensure adequate coverage of the area for
stimulation

24.  In some circumstances, a bipolar method is preferable if a
longitudinal zone requires stimulation rather than an
isolated tissue area.
 Placement of the electrodes should be such that a crossover
effect is achieved in the desired area.
 If the electrodes are not placed so that a crossover is
achieved, the physiological effects of I/F cannot be
achieved.
 A sweep (or gradually changing frequency) is often used to
overcome this problem (as well as generating a range of
effects).
 The sweep (range) should be appropriate to the desired
physiological effects, though again it is suggested that an
excessive range may minimise the clinical effect.
 The mode of delivery of the selected sweep varies with
machines.
 The most common application is the 6 second rise and fall
between the pre-set frequencies.

25.  For example, if a 10 to 25 Hz range has been selected,
the machine will deliver a changing frequency, starting
at 10 Hz, rising to 25 Hz over a 6 second period. Once
this upper limit has been achieved, the frequency will
once again fall, over a 6 second period to its starting
point at 10 Hz. This pattern is repeated throughout the
treatment session
 Treatment times vary widely according to the usual
clinical parameters of acute/ chronic conditions and
the type of physiological effect desired.
 In acute conditions, shorter treatment times of 5 to 10
minutes may be sufficient to achieve the effect. In
other circumstances, it may be necessary to stimulate
the tissues for 20 to 30 minutes.

26. 1. Plate
2. Pen
3. Vacuum
PLATE ELECTRODES :
 Made form conducting rubber
 Comfortable and long lasting
 Larger plates electrodes = deeper effect
 Smaller plates electrodes = superficial effect , localized effect
 Attached with strap for good contact
VACUUM ELECTRODES
 Made forma vacuum unit plug into a rubber suction cup connected to a
machine
 Suction should not be apply constant because it can be uncomfortable and
causes burning
 For better adherence = placed wet spongers in the cup and moisten the edges
 For excellent treatment = flat smooth area [ back or plump knee ]
 Hairy area = not apply because cant’s get airtight seal

27.  For Interferential therapy use to for electrodes [ 2 pair electrodes ]
 Each pair indicated by the colouring wire form the machine .
 2 electrodes = black and 2 electrodes = red .
 So in pair = 1 electrode black and 1 electrode red .
 The electrodes of each pair are placed diagonally opposite one another .
 So that beat frequency is produced in the tissue where it required .

28.  First of all on the plinth placed 4 electrode in positing of electrode .
 After that put the hand on centre of the electrodes .
 Then increase to intensity and feel to current .
Technique of treatment of Interferential
therapy :
 Patient position = comfortable .
 Skin = washed and apply petroleum jelly on the lesions .
 After that place the electrode on the site of treatment .
 Instruct to patient if feel a tingling sensation please tell to therapist .
 On that time decrease the intensity .
Technique of treatment
with plate electrode
Technique of
treatment with
vacuum
electrode

30. Pain relief
 The increase in local blood circulation due to the the local pumping
effect of the stimulated muscles effect on autonomic nervous and does
the blood vessels help removing the chemicals from the local area
 It is achieved by stimulation of articular formation at 25 Hz or bye
blocking c fibre at 50 Hz
Muscle stimulation
 It is possible to continue to stimulate the muscle we on its point of
fatigue
 Useful for the simulation of both
Motor and sensory nerves
Blood flow
 Deep tissue penetration stimulates parasympathetic nerves fibres for
increased blood flow
 Increases blood flow
Reduces oedema
 Improves venous drainage

31.  Pain relief
 Oedema control
CONTRAINDICATIONS
 Cardiac pacemaker
 Hypertension
 Thrombosis
 Haemorrhage
 Pregnancy
 Neoplasm
 TB
 Fever
 Infections

32.  Burn
 Increased pain-intensity too high electrodes touch the skin
 General malaise
 Nausea
 Dizziness
 Headache
PRECAUTIONS
 Epileptic patients
 Over anterior chest wall
 Position suction electrodes below the level of damage
/discomfort

33. The tissue does not adapt to a certain frequency and thus a
given treatment can be performed for a longer period and
repeated more often
 How IFT is used for pain relief,
• Activation of a Aδ pain fibres through electrical pulses of
high intensity and low frequency provokes impulses in the
midbrain, that travel back down the spinal cord to inhibit
the C-system cells through secretion of encephalin
• Encephalin secretion at the substantia gelatinosa rolando
(lamina II) leads to the inhibition of transmission of C fibres
signals to the CNS producing analgesic effect
• This is achieved by the application of the the high intensity
low frequency IFT

34.  Electrotherapy for Physiotherapists
By Virendra Kr.Khokhar
 Handbook of Practical Electrotherapy
By Pushpal Kumar Mitra

35.  A Comparative Study on Effect of IFT and Conventional Exercises Versus ICT And
Conventional Exercises in Cervical Spondylosis.
Minal Dhairya Bhavsar
IFT and ICT are used in patients with cervical spondylosis. The purpose of this study is to
compare the effects of IFT and ICT in patients with cervical spondylosis.
Conclusion:-When the results were analyzed using “T-test” it shows that there is significant
effect of IFT plus conventional exercises on pain compared to ICT plus conventional
exercises.
 Comparative Effect of Burst Transcutaneous Electrical Nerve Stimulation (Tens)
Versus Interferential Therapy (Ift) Along With Exercise In Reducing Pain and
Functional
Mahima Mukharjee, Ronald Prabhakar
A comparative study was done where two groups were made, Group A (n= 10) received
burst transcutaneous electrical nerve stimulation along with exercises and Group B (n=
10) received interferential therapy along with exercise
Conclusion: The study concluded that Interferential Therapy along with Exercises is more
effective than Burst Transcutaneous Electrical Nerve Stimulation along with Exercise.

36.  Effect of interferential therapy to decrease lumbar Hyperlordosis: a systemic review
Afif Shakirin Bin Sirat
This study is conducted to understand the effect of interferential therapy (IFT) in the process of
decreasing the lumbar Hyperlordosis.
Conclusion: Applying interferential therapy (IFT) alone will not decrease the curve of
Hyperlordosis, however, it has an analgesic effect and reduces pain and promote relaxation of
the muscles which could help the process of reducing the Hyperlordosis with the combination of
exercises and other treatments.
 International journal of physical education, sports and health effectiveness of
interferential therapy and transcutaneous electrical nerve stimulation and Pilates
exercise program in non-specific low back pain patients -A comparative study
Chaithanya K, Sharath URS, Radha Krishna and Archana P
In this study, patients with chronic Non-specific low back ache of both the sex were randomly
divided into group A and group B. Group A were treated with Interferential therapy for 30
minutes for 2 weeks and Pilates exercise for 4 weeks,3 days per week. Group B were treated
with Transcutaneous electrical stimulation for 30 minutes for 2 weeks and
conclusion: PilatesGroup A; Interferential therapy and Pilates exercises showed better
improvement when compared with Group B; Transcutaneous electrical nerve stimulation and
Pilates exercises. Hence, Interferential therapy and pilates exercise are the better line of
treatment than Transcutaneous electrical nerve stimulation and Pilate’s exercises in treating
chronic non-specific low back ache exercises for 4 weeks, 3days per week. Both the groups
were treated for 6 weeks.