IFT, PRINCIPLES, TYPES OF ELECTRODES, METHODS, INDICATIONS, CONTRAINDICATIONS, THERAPEUTIC EFFECTS

1. PREPARED BY :- NIYATI PATEL
INTERFERENTIAL THERAPY
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2. INTRODUCTION
 Interferential current was developed in the
1950s by Dr Hans Nemec in Vienna, and
became increasingly popular in the UK during
the 1970s.
 So it is also known as Nemec’s current.
 Interferential current is the waveform produced
by the interference of two medium frequency
currents are used to produce a low frequency
effect.
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3.  Two medium frequency currents which are slightly
out of phase, passed through the tissues
simultaneously, where they are set up so that their
paths cross and in simple terms they interfere with
each other.
 This interference gives rise to an interference or
beat frequency which has the characteristics of a
low frequency stimulation.
 Two medium-frequency currents are used to produce
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4. Principle of Interferential Therapy
 The basic principle of Interferential Therapy (IF) is
to utilize the strong physiological effects of low
frequency electrical stimulation of muscle and
nerve tissues at sufficient depth without the
associated painful and somewhat unpleasant side
effects of such stimulation.
 Interference produced by two currents in the
tissues is called the beat frequency.
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5.  The resistance (impedance) of the skin is inversely
proportional to the frequency of the stimulation.
 In other words, the lower the stimulation frequency,
the greater the resistance to the passage of the
current
 i.e. Z = 1/2𝜋fC
 The skin impedance at 50Hz is approximately 3200
ohms whilst at 4000Hz it is reduced to
approximately 40 ohms.
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6.  Medium frequency currents of around 4000Hz
, while able to stimulate motor and sensory
nerves, encounter a much lower skin
impedance.
 These two waveforms are delivered through
two sets of electrodes through separate
channels in the same stimulator.
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7. PHYSICAL PRINCIPLES
 These currents are of medium frequency i.e.
4000 or 5000 Hz that rhythmically increases and
decreases in amplitude at low frequency.
 One current is normally of fixed frequency, for
example at 4000Hz, and the other current is
adjustable, for example between 4000 and
4200Hz.
 The two currents summate or cancel out each
other in a predictable manner, producing the
resultant amplitude-modulated
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9.  A : 4000Hz (carrier frequency)
 B : 3900Hz
produces a resultant ‘interferential current’
 C : Amplitude modulated frequency of 100Hz
4000
4000
3900
3900
100
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10. PRINCIPLES OF WAVE INTERFERENCE
 CONSTRUCTIVE
 DESTRUCTIVE
 CONTINUOUS
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11. Principles of wave interference: Combined
Effects
 Constructive interference: when two
sinusoidal waves that are exactly in phase
or one, two or three wavelengths out of
phase, the waves supplement each other in
constructiveinterference
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12. Principles of wave interference: Combined
Effects
 Destructive interference: when the two
waves are different by half wavelength (of
any multiple) the result is cancellation of
bothwaves
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13. Principles of wave interference: Combined
Effects
 Continuous Interference: Twowaves slightly
outof phase collide and form a single wave
with progressively increasing and
decreasing amplitude
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14. TYPES OF ELECTRODES
Three types of electrodes :
1. Plate electrode
2. Vacuum electrode
3. Combined
electrode
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15. PLATE ELECTRODE
 Made of conducting rubber which are
comfortable and long lasting
 larger plates electrodes give more
comfortable treatment and deeper effect
 Smaller electrodes are used for a localized
effect, but this effect is more superficial
 Attached to the patient by means of straps to
assure a good contact and greater tolerance
of treatment
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16. VACUUM ELECTRODE
 Made from a vacuum unit plug into a rubber
suction cup connected to a machine
capable of producing a vacuum,
 Suction should not be constant because it
can be uncomfortable and causes bruising
 Wet sponges are placed in the cups and
moisten the edges of the cups for better
adherence,
 Excellent for treating flat smooth areas for
example back or aplump knee
 Not indicated for treatment of the hairy areas
because can’t get an airtightseal
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18. COMBINED ELECTRODE
 all four contacts are embedded in some
insulating material and can be applied as one
pad
 there are different sizes (small, medium and
large) for different surfaces to be treated
 limited by the low intensity of current that can
be tolerated so general effect is small
 if possible, use larger separate plate
electrodes!!
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19. METHOD OF APPLICATION
 Two methods,
1. QUADRIPOLAR application
2. BIPOLAR application
3. QUADRIPOLAR method with
AUTOMATIC VACTOR SCAN
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20. QUADRI-POLAR TECHNIQUE.
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21. QUADRI-POLAR TECHNIQUE.
 The four electrodes are positioned around the
target treated area so that each channel runs
perpendicular to the other and the current crosses
at a midpoint.
 The interference effect branch off from the center
of the treated area in the shape of a four leaf
clover.
 Tissues within this area receive the maximal
treatment effect .
 The electrodes are positioned in a coplanar
arrangement to treat a flat surface .
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22. QUADRI-POLAR TECHNIQUE
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23. COPLANAR APPLICATION FOR
BACK.
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24.  The maximum AMF is obtained in the
intersection of the two applied alternating
currents. (point of superimposition)
 Balance control : to allow the output of one
channel to be increased while decreasing the
other.
 USE : for selective stimulation of deeper lying
tissue.
and highly suitable for shoulder, knee,
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25. QUADRIPOLAR [4EL]
 4 electrodes supplied by two channels.
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26. BIPOLAR [2EL]
 In this mode, the AMF is generated inside the
equipment and supplied to the patient through
two electrodes.
 This method makes it very easy to localise the
area of stimulation because the AMF is
present in the entire region between the two
electrodes.
 USE : suitable for the treatment trigger points,
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27.  Disadv. of bipolar mode is more sensory
stimulation, since the low freq. current is
already produced by the machine, and has to
go through the skin and it is unpleasant
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28. BIPOLAR TECHNIQUE
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29. QUADRIPOLAR METHOD USING
AUTOMATIC VECTOR SCAN
 4EL 45 OR 4EL 90
 In this technique, the intensity of the alternating
currents is varied.
 As a results, a point of superimposition rotates
within the area of intersection enlarging the area of
effective treatment.
 USE : suitable when the point to be treated can not
be exactly localised.
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30. TREATMENT PARAMETERS
 AMPLITUDE MODULATED FREQUENCY
 FREQUENCY SWEEP
 CURRENT INTENSITY
 TREATMENT DURATION
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31. FREQUENCY
 Excitable tissues can be stimulated by low
frequency alternating currents. Although to
some extent, all tissues in this category will be
affected by a broad range of stimulations, it is
thought that different tissues will have an
optimal stimulation band,
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32. These are detailed frequencies below:
 Sympathetic Nerve 1-5Hz
 Parasympathetic Nerve 10-150Hz
 Motor Nerve 10-50Hz
 Sensory Nerve 90-100Hz
 Nociceptive fibers 90-150Hz
 Smooth Muscle 0-10Hz
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33. SWEEP FREQUENCY
 Nerves will accommodate to a constant signal &
a sweep (or gradually changing frequency) is
often used to overcome this problem.
 The sweep (range) should be appropriate to the
desired physiological effects, 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.
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34. SWEEP FREQUENCY
 For example, if a 10-25 Hz range has been
selected, the machine will deliver a changing
frequency, starting at 10 Hz, rising to 25Hz
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 10Hz.
 This pattern is repeated throughout the
treatment session.
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36. Other patterns of sweep can be
produced on many machines
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37. CURRENT INTENSITY
 The intensity of the current is dependent on the
desired physiological effect and the tissue to be
stimulated.
 In general the current could be administered at
sensory level, motor level, or noxious level.
 Use an intensity of current which produces a strong
but comfortable prickling without a muscular
contraction.
 Steps to follow:
1) Increase current until the patient feels a definite prickling, and
leave for one minute for it to decrease
2) Increase current again until the patient reports a slight
muscular contraction, then decrease until contraction stops.
 may teach the patient to increase intensity periodically
in order to obtain longer lasting pain relief
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38. DURATION OF TREATMENT
 IFC usually applied for 10-15 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 è total time
should not exceed 30 min.
 Vary widely according to the usual clinical
parameters of acute/chronic conditions & the type of
physiological effect desired.
 Acute conditions 5-10 minutes
 Chronic conditions 20-30 minutes
 **too long a Rx makes pt. unacceptably tired later in
the day!**
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39. FREQUENCY OF TREATMENT
 in most cases, treatment every other day (i.e.
3x/wk.) is ideal
 treatment less than twice/week is usually a
waste of time
 a course of 12 treatments is given
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40. WAVEFORMS
 TRIANGULAR –acute condition
 RECTEANGULAR- sub acute condition
 TRAPEZOIDAL-chronic condition
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41. Uses of Interferential Therapy
The are 5 main clinical uses for which IF appears
to be beneficial:
 1- Relief and management of acute and chronic
pain.
 2- Muscle stimulation
 3- Increased blood flow
 4- Reduction of edema
 5- Stimulating of soft tissues healing and repair.
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42. 1. Relief of Pain
 important because pain produces spasm, unnatural
movement, and production of more strain.
 IF current is used management of acute and chronic
pain of different origin specially Post traumatic pain
Sympathetically maintained pain as in shoulder hand
syndrome, reflex sympathetic dystrophy and Reynolds
disease
*IFC is not effective in post-traumatic pain in the acute
stages!! It is effective in cases of chronic pain with or
without swelling.
 set F at 80-100Hz which gives analgesic effect with a
vasodilatory effect on the tissues.
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43. Mechanisms of Pain control by interferential therapy
 Stimulation with the higher frequencies about
100Hz at sensory level stimulation stimulate the
pain gate mechanisms & thereby mask the pain
symptoms.
 Stimulation with lower frequencies up to 10Hz at
motor level intensities can be used to activate the
opoid mechanisms, again providing a degree of
relief.
 Decrease activity of the sympathetic ganglion and
sympathetic nerves in cases of sympathetically
maintained pain.
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44. 2. Muscle contraction Stimulation
 Stimulation of the motor nerves to induce
contraction of muscle can be achieved with a
wide range of frequencies (10-50Hz). Clearly,
stimulation at low frequency (e.g. 1-10Hz) will
result in a series of twitches, with stimulation at
50Hz will result in a tetanic contraction. The
choice of treatment parameters will depend on
the desired effect.
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45. 2. Muscle contraction Stimulation
If IF is used as neuromuscular stimulation, it can
be used for:
 Relaxation of muscle spasm.
 Prevention and retardation of disuse atrophy.
 Muscle re-education.
 Maintenance of range of motion.
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46. 3. Increase blood flow
 Increased vasodilatation is noticed following
interferential current due to Its effect on
parasympathetic nerve fibers for increased blood
flow.
 IC is used in treatment of circulatory disorders,
Depressing the activity of certain cervical and
lumbo-sacral sympathetic ganglia in patients with
increased arterial constrictor tone so increased
circulation a in Raynaud’s disease.
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47. 4. REDUCTION OF SWELLING & EDEMA
 important because organization of the exudate
leads to the formation of adhesions and
impairment of function
 set F at 1-30Hz which causes
a. electroporation (increased permeability of the
cell membrane, which helps ion movement to and
from cells)
b. increase in venous and lymphatic flow, and
increase tone of tissues and vessels which aid in
the relief of edema
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48.  Chronic post-traumatic edema can be reduced
by the use of IF. This effect is attributed to
milking of the venous and lymphatic return
through electrically evoked contraction.
 progress Rx by setting beat F at 1-15Hz or a
sweep of 10-25 Hz which causes vasodilation,
and has a vigorous pumping effect which will
increase the physiologic mechanisms for the
absorption of the exudate.
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49. 5. Stimulating soft tissues healing and repair
 IF improve accelerate ossification and is used
to enhance fracture healing.
 IF current also is used to accelerate wound
healing by improving cellular function and
increasing cell proliferation.
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50. Contraindications
 1)Arterial disease
-the stimulatory effect of the current could
produce emboli
 2) Deep Vein Thrombosis
-in the acute phase, it is possible to dislodge the
thrombi or increase the inflammation of the
phlebitis
 3) Infective conditions
-could spread the infection or exacerbate due to
the stimulatory effects of the current
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51. `
 4) Pregnant Uterus
-not safe for fetus
-may however use for S.I. joint strain during pregnancy
if IFC placed superficially over S.I. ligaments
 5) Danger of haemorrhage
-stimulating effect can cause an Ý in bleeding
 6) Malignant tumors
-direct stimulation of tumor is CI, but reffered pain from
cancer or metastasis can be treated
 7) Artificial pacemakers
-a demand unit must sense the electrical activity of the
heart, thus avoid an electric device that may interfere
with it
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52.  8) Large open wounds
-these will cause concentration of the current
and distortion of the IF field
 9) Dermatological conditions
-IFC may exacerbate any dermatological
condition in the area being treated
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53. Set-up and Application
 The usual steps for preparation of patient and the
apparatus during electrical stimulation are followed.
 Apply the electrodes to the treated.
 Turn on the apparatus by activating the power switch.
 Select the appropriate beat frequency based on the
goal of treatment.
 Use the appropriate sweep frequency for this
treatment protocol.
 Set the duration of the treatment by adjusting the
timer.
 Start the treatment by pressing the start button.
 Slowly increase the intensity until the appropriate
current level is obtained and guided by the patient’s
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54. Precautions
 care should be taken to maintain the suction at a
level below that which causes damage or
discomfort to the patient.
 For patients who have febrile conditions, the
outcome of the first treatment should be monitors.
 Patients who have epilepsy, advanced
cardiovascular conditions or cardiac arrhythmias
should be treated in consultation with the
appropriate medical practitioner.
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55. REFERENCES
 1. Electrotherapy - evidence-based practice,
by Sheila kitchen, 11th edition, pg no. 287-300
 2. Physical agents in rehabilitation – from
research to practice
 3. Clayton’s Electrotherapy – theory and practice,
ninth edition, pg no. 107-111.
 4. Physical principles explained by low n reed,
pg no. – 128.
 5. Therapeutic modalities in rehabilitation, by
William E. Prentice, 3th edition
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