1) Interferential therapy involves applying two alternating medium-frequency currents that intersect in the body tissue to produce an interference beat frequency current for therapeutic purposes. 2) The beat frequency current can stimulate different tissues at different frequencies - nerves at 1-150Hz, muscles at 1-100Hz, increasing blood flow at 10-25Hz, and reducing edema at 1-10Hz. 3) Indications for interferential therapy include relief of chronic pain, absorption of exudates, and stress incontinence. General contraindications include pacemakers, malignancy, and infections. Local contraindications include open wounds and metal in the skin.

1. Electrotherapy
DR RIAZ AHMED PT
LECTURER

2. Medium Frequency Current
Medium frequency current are the current
whose frequency fall between the range of 1000 to
10000 Htz.
ADVANTAGES
1)Greater penetration
2) High tolerance and comport
3) Can be used for pain and muscle stimulation
4) Low skin resistance

3. Types
1) Rebox-type current: rebox electrotherapeutic
method is based on non invasive transcutaneous
application of specific current to a living tissue. it is
used for acute and chronic pain, immobility
musculoskeletal and neurological disorders.
2) Russian current: The Russian current waveform is
type of electrical stimulation that delivers medium
frequency current in alternating pulses or burstof
energy. .
3) Interferential therapy

4. Interferential therapy
Historical Background
Introduced by Dr. Nemec in Vienna in the early 1950’s.
Definition: The transcutaneous application of
alternating medium-frequency electrical currents,
amplitude modulated at low frequency for therapeutic
purposes.
Or
It is the resultant current produced when two or more
alternating current are applied simultaneously at the point
of intersection in a given medium.

5. Definitions
Impedance:-The effective resistance of an
electric circuit or component to alternating current,
arising from the combined effects of ohmic resistance.
Modulation is the process of varying one or more
properties of a periodic waveform.
Beat Frequency The interference produced by
the two current in the tissue is called beat frequency

10. Basic Principles of ITF
 The ITF depends upon the interferential effect of two
medium frequency currents crossing in the patient
tissue. The interference produced by the two current
in the tissue is called beat frequency.

11. Let us take two medium frequency current in circuit A
=4000Hz and circuit B=3900 Hz. Where these two
current are applied to the tissues, at he point where
current cross over, a new beat frequency current is
setup whose amplitude is modulated and the
frequency of the new current is called beat frequency
(Interferential current).
Current A: f1 (this current is set on the machine,
thus called “intrinsic/carrier frequency”)
Current B: f2 (same amplitude, but slightly higher
frequency; therapist sets this one)
F=f1-f2=4000-3900=100Hz
Frequency range can be produced 1-250Hz

12. Physiological Effects of ITF
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 (Savage 1984) that different tissues will have
an optimal stimulation band, which can be estimated by the conduction
velocity of the tissue.
These are detailed below:
Sympathetic Nerve 1-5Hz
Parasympathetic Nerve 10-150Hz
Motor Nerve 10-50Hz
Sensory Nerve 90-100Hz
Nociceptive fibers 90-150Hz (?130Hz specific)
Smooth Muscle 0-10Hz
The clinical application of I/F therapy can be based logically
on this.

13. The are 4 main clinical applications for which I/F
appears to be used:
Pain relief
Muscle stimulation
Increased blood flow
Reduction of oedema

14. Pain Relief:
Higher frequencies (90-150Hz) to stimulate the pain
gate mechanisms & thereby mask the pain symptoms.
Short duration pulses at a frequency of 100Hz may
stimulate large diameter nerve fibers which will have
an effect on the pain gate in the posterior horn, and
inhibit transmission of small diameter nociceptive
traffic.

15. Muscle Stimulation
Stimulation of the motor nerves can be achieved with a wide
range of frequencies.
Range 1-100Hz
stimulation at
low frequency (e.g. 1-5Hz) will result in a twitches
(5-20Hz) Partial tetany
30-100Hz Tetanic contraction.
The choice of treatment parameters will depend
on the desired effect, but to combine muscle stimulation
with an increase in blood flow and a possible reduction in
edema, there is some logic in selecting a range which does
not involve strong sustained tetanic contraction & a sweep
of 10-25Hz is often used.

16. Increased blood flow
combine muscle stimulation with an increase in
blood flow and a possible reduction in oedema,
there is some logic in selecting a range which does
not involve strong sustained
tetanic contraction & a sweep of 10-25Hz is often
used.

17. Reduction of oedema
 This is accelerated by a frequency of 1-10Hz
rhythmic, as a rhythmical pumping action is
produced by muscle contraction, and there
is possible effect on autonomic nerves which
can effect the diameter of blood vessels, and
therefore the circulation. Both of these
factors will help absorb exudates and thus
reduce swelling.

18. INDICATION
1. Relief of chronic pain
(i) Low back pain
(ii) Periarthritis shoulder
(iii) Osteoarthritis knee
2. Absorption of exudates
3. Stress incontinence

19. Contraindications(General)
 Pacemakers
 Malignancy
 Pregnancy
 Bacterial Infections
 Thrombosis
Fever
 Hypertension
 Anemia
 Sever renal and cardiac failure

20. Deep X-ray and cobalt
therapy
Epileptic patients
Non cooperative patients
Mentally retarded patients
Very poor general condition
of the patient

21. Contraindications (Local)
 Open wounds
 Very recent fractures
 Skin grafts
 Severe edema
 Hairy surface
 Acute inflammation
 Metal in the part
 Hypersensitive skin
 Loss of sensation

22. Methods of treatment
 Skin must be clean and clear before the start of the
treatment
 The part of the body to be treated should be washed and if
there is any skin lesion it should be covered by applying
petroleum jelly on it.
 The electrodes should be placed in such a way that the
crossing point of two currents lie above or around the
affected part.
 The suitable frequency current should be given for different
conditions.
 Increase the power gently and cautiously until the
patient starts feeling the current. It can be increased
till the patient can tolerate.

23. Preparation of Apparatus
1. Check whether all the knobs are at zero
2. Checking the pins of the plugs and check
whether the switch is turned off
3. Check the insulation of wire
4. Check whether the switch in the
stimulator is working
5. Check whether fuse is present
6. Check whether hand switch of patients
use is intact and working