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Medium Frequency Currents IFT

Medium Frequency Currents IFT it is the medium frequency current in interferential therapy.It is used for significant physiological effects of medium frequency.


  • Frequency ranges from 1 kHz to 100 kHz
  • Longer wavelengths (>10 mm)
  • Effects occur at deeper structures
  • General effects:

MFC: blocks pain

LFC: nerve stimulation

  • Sample modalities:

◦Electrical stimulators, Didynamics, Biofeedback,
Iontophoresis, TENS, IT—


A unit of stimulating current

Otherwise known as a PHASE (current phase)

Can be more fully described according to DURATION (pulse duration expressed in seconds), INTENSITY  (current intensity expressed in amperes or volts), and SHAPE (waveform)


  • Amount of time needed for the rise and fall pattern to occur at a given pulse
  • Expressed in SECONDS (millisecond=ms)


  • The rate of flow of electrons
  • Usually expressed in AMPERES (milliamperes = mA)


  • Describes the rise-and-fall pattern of a pulse
  • The shape of the waveform reflects the time required for the current to reach the maximum intensity
  • Waveforms with a sudden rise in intensity are suitable for innervated muscle
  • Waveforms with slowly rising intensity are best suited for denervated muscle


  • A rate of change of an electrical pulse
  • Expressed in HERTZ (Hz)




—Therapeutic/Clinical Uses…

Assists in functional training

Assists in muscle force generation and contraction

Decreases unwanted muscle activity

Increases rate of healing of open wounds and soft

Helps maintain muscle integrity after surgery

Modulates and/or decreases pain

Decreases or eliminates soft tissue swelling,
inflammation, or restriction


1)Direct Currents

2)Alternating Currents

3)Pulsed Currents

Noted Characteristics…


◦ Frequency (Hz)

◦ Pulse duration


◦ Number of PHASES

◦ Shape and symmetry of WAVEFORMS


—Direct Current

—Refers to a current passing continuously in the same direction (unidirectional current)


—Direct Current (cont.)


◦ Constant Current

◦ Galvanic Current / Galvanism

Galvanic stimulation is useful only for stimulating
denervated muscles

Interrupted Direct Current (IDC) is used to stimulate
innervated muscles

Direct current is also used in IONTOPHORESIS

—Direct Current (cont.)

 Types of IDC:

1.Long Duration IDC

◦> 1 ms

◦For sensory and motor nerve stimulation (denervated)

2.Short duration IDC (Faradic-Type)

< 1 ms

◦For pain control and nerve stimulation (innervated)


—Alternating Current

—Defined as a continuous or uninterrupted bidirectional flow of charged particles

—Alternating Current (cont.)


1.Sinusoidal Current

◦Evenly alternating sine wave currents of 50 Hz

◦For pain relief, edema, and improvement of circulation

2.Dynamic Current

◦Rectified monophasic sinusoidal current

◦For pain relief, tissue healing, muscle re-education and improvement of circulation


—Pulsed Current


  • Defined as the uni- or bi-directional flow of charged particles that periodically ceases for a finite period of time


—Medium Frequency Currents
  • Medium frequency currents are the currents which a frequency falling between the range of 1000 to 10000Hz(1 kilohertz to 100 kilohertz)
  • Used therapeutically due to their advantage over the low-frequency current
  1. greater penetration,
  2. higher tolerance and

III.  comfort


—It is the application of alternating medium frequency currents to produce a low-frequency effect for therapeutic purpose.

—Low-frequency stimulators have the problem of skin resistance and produce skin irritation(pain).

—High frequency will not stimulate nerve because their pulse duration is less than 0.01msec., having thermal effect.

—To overcome the skin resistance, two medium frequency currents are interfered to produce a low-frequency effect.



Z= 1/2FC

Where Z – Impedance (Ohms)

F – Frequency (Hz)

C – Capacity of the skin (microfarads)


So the skin resistance reduces with increase in frequency.



The physiological effect on the tissues depends upon:


—Use of constant/swing frequency

—Intensity of the current

—Accuracy of electrode placement

—Location of lesion

—Tissue type and underlying pathology.


1)Effect on pain:

  • “Analgesic effect of IC”
  • Pain relief due to the following reasons:
  • Effect on the pain gate (90-100Hz)
  • Increased circulation (0-100Hz, 90-100Hz)
  • A physiological block of nerve conduction (above 40 Hz).

—Motor stimulation effect on the weak nerve:

  • Innervated muscles are stimulated
  • Both skeletal and smooth muscles are stimulated, which is not possible with faradic currents.
  • Very little sensory stimulation
  • Helpful to stimulate deep muscles (pelvic muscles), rhythmic contraction.


2)Effect of edema:

◦Absorption of exudation is possible when using  1- 10 rhythmic and 1- 100 rhythmic.

◦Causing  pumping  action on the muscles

◦Increased blood supply

◦Removal of exudates, swelling and edema.

3)Effect on muscle spasm:

  • Causes muscle relaxation by
  • Increased vasodilation
  • Removal of pain stimuli
  • Breaks the pain-spasm cycle.—

4)Sympathetic  dysfunction:

  • Reflex sympathetic dystrophy,
  • Shoulder-hand syndrome,
  • Neuralgia,
  • Migraine of sympathetic cause and
  • atrophy.
  • (Vasomotor tone is increased due to sympathetic activity)



—Trigger point

—Stress incontinence

—Degenerative joint diseases

—Muscle spasm

—Venous & lymphatic drainage

—Re-education of deeply situated muscles

—Phantom pain

—Inflammatory conditions


—Arterial  and venous diseases

—Infective conditions

—Pregnant uterus

—Hemorrhage and menstruation.

—Malignant tissues

—Artificial pacemaker

—Cardiac problems

—Unreliable patient

—Dermatological conditions—


—Electrical burns: due to bare metal electrodes, skin currents, increased intensity, and interference by other modalities.


— Increased pain

— General malaise



—Dizziness and faintness

—Neurological defects.




Dosage is divided into

  • Low dosage- not felt by the patient
  • Medium dosage – just a noticeable feel
  • High dosage – experience and pleasant
  • Very high dosage – strong vigorous and unpleasant.
Interferential therapy can be applied according to the following criteria:
  • 10-20 minutes
  • For 10 to 25 days
  • once a day basis

—Types of Electrodes :

Metal plate electrodes

Carbon rubber electrodes

Vacuum(suction) electrodes



  1. Metal plate electrodes:

—Metal plate of variable size encased in a sponge/lint pad

—Water socked / moistened  with water before application


  1. Carbon rubber electrodes:
  • Variable shape (circular/ square) made of rubber
  • Used with conducting gel

  1. Suction electrodes:
  • Flexible rubber cups
  • An electrode is kept at the base of cup and wire or lead is connected at the narrow end.
  • The tube connects to the pump of the machine

—Generally, a soaked sponge is kept just below the electrodes so as to achieve even contact to skin and hence better conduction

—Advantage- of mild massage effect on the skin stimulates cutaneous sensory nerve endings causing vasodilation.

—Disadvantage-  cannot be used if the skin condition is poor (edema/ elderly patient)


Preparation of the apparatus:

—Checking the machine to ensure the knobs are at zero

—Any break in the electrodes and wires

—Preparation of the tray:




Pillows and tools


Preparation of the patient:
  • Explanation about the treatment
  • Expose the part
  • Check the contraindications
  • Skin sensation testing for pricking using cotton and pin
  • Wash the treatment part with saline to remove all grease/dirt.


—Positioning the patient

◦Comfortably with an area to be treated adequately supported


◦Soak the pad/lint electrodes with 1% saline water

Methods of application:

  1. Quadripolar method
  2. Bipolar method
  3. Stereodynamic
  4. Labile method



1.Quadripolar method:

—  Via  4 electrodes

  1. a) Static quadripolar:

–The electrodes are placed diagonally to each other

–The interference takes place in the middle and the clover pattern is static.


  1. b) Vector quadripolar (dynamic interference)

–The electrodes are placed diagonally to each other

–The interference takes place in the middle and the clover pattern rotates at an angle of 45 degrees.

2.Bipolar method:
  • Pre modulated method
  • Via using 2 electrodes
  • Modulated inside the machine.
  • 2 red or 2 black used.—

3.Stereodynamic system:

  • three pairs of electrodes are used
  • The machine provides three outputs
  • It reduces accommodation and provides three-
    dimensional interferential field
  • Although, with the aid of the two-field interferential current technique, the site of stimulation can be displaced into the depth of the body and, with appropriate equipment, it is not possible to involve all areas of the body within the stimulating effect. All the areas located outside of the area demarcated, are not stimulated unless the electrodes are repositioned. If, however, a third field is added to the two existing fields, the resulting field strength vector can “move out of” the area and pass along any spatial direction, that is, can “reach” any structure within the area to be treated (spatial stimulation = stereo stimulation.

4.Labile Method:

  • Two labile electrodes are used for the treatment
  • An operator moves them during the treatment

Interferential apparatus must be kept at least 6meters distance away from shortwave diathermy apparatus

Otherwise, circuit damage can occur or a patient may experience a sudden surge of currents when the shortwave diathermy machine is turned off

To avoid this a filter circuit can be used in interferential therapy machine


—Does not produce any sensory and motor irritation

—Metal is not contraindicated in interferential therapy

—Useful in treating tissues at greater depth

—Current is localized more effectively in specific areas


—Medium frequency currents





—Physiological effects

—Therapeutic effects

—Indications and contraindications


—Dosage and application