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Definition: Interferential Current Interferential current is a type of electrical stimulating current that overcome the problem of poor penetration encountered by low frequency currents.It has advantage over faradic

current stimulation that faradic currents can only stimulate voluntary components.The exact frequency of the resultant beat frequency can be controlled by the input frequencies e.g., if one current was at 4000 HZ and its companion current at 3900 HZ, the resultant beat frequency would be at 100 HZ. Physics of IF current: The basic principle of Interferential Therapy is to produce low frequency electrical stimulation of the muscle and nerve (less than 250 Hz) without the associated unpleasant sensation of the low frequency stimulation.Pain Control: High beat frequencies, about 100 Hz, when accompanied by sensory-level stimulation, activate the spinal gate, inhibiting the transmission of noxious impulses.Carbon-rubber electrodes in different Suction electrodes shapes Electrodes placement: Quadripolar Technique The four electrodes are positioned around the painful area so that each channel runs perpendicular to the other and the current crosses at the midpoint.Bipolar Electrode Placement When IFS is applied using a bipolar technique, the mixing of the two channels occurs within the generator rather than in the tissues.These two effects will encourage the reabsorption of tissue fluid and milking of the venous and lymphatic return through electrically evoked contraction.The resulting interference currents are in a range that allows effective stimulation of deeper tissues than other forms of electrical stimulation with relatively little patient discomfort.- Frequency: the current frequency is about 4000 Hz but beat frequency is dependent on the desired effect; a. Sensory nerves: 90 - 100 Hz. b. Motor nerves: 1 - 50 Hz. c. Smooth muscle fibers: 0 - 10 Hz.

• Intensity: The current intensity is typically in the range of 0 - 100 mA which is dependent on the desired effect (sensory or motor stimulation).Sweep patterns; a) triangular pattern, b) rectangular pattern and c) trapezoidal pattern Physiological effect: The main clinical applications of IFT are: a. Painrelief.a. Stimulationatlowfrequencyof1-30Hzwillresultina series of twitches (the most effective motor stimulation frequency is 10-25 Hz) b. Stimulation at 50 Hz or more will result in a tetanic contraction.Two electrodes were placed on the lower abdomen just above the outer half of the inguinal ligament and another two on the inner aspect of thigh near to the origin of adductor muscle.At low frequencies a twitch is produced, between 5 and 20 Hz a partial tetany and 30 to 100 Hz tetanic contraction occurs.It is claimed that the rapid return of the tone of pelvic floor muscles occurs when treated with interferential therapy due to stimulation of both voluntary and smooth muscle fibers.It utilizes two medium frequency currents (generated from two different circuits), passed through the tissues simultaneously.Increasing the frequency to 4000 Hz reduces capacitive skin resistance to approximately 40 ohms.Consequently, IFS encounter less skin resistance and can pass to deeper tissues with using less current intensity than other low-frequency forms of stimulation.- Frequency Sweep: accommodation is a characteristic feature of the excitable tissues (nerves and muscles) if they are stimulated using fixed frequency.Low beat frequencies of 2 to 10 Hz, applied at the motor level, should initiate the release of opiates and result in a narcotic-like pain reduction.The medium frequency carrier currents penetrate the tissues with very little resistance.An AC of 50 Hz encounters approximately 3000 ohms of resistance per 100 cm2 of skin.Parameters of Interferential current:
• Waveform: biphasic symmetric balanced sine wave.c. Surged stimulation mode might be advantageous in reducing fatigue.d. Reduction of edema.2.3.

Definition:
Interferential Current
Interferential current is a type of electrical stimulating current that overcome the problem of poor penetration encountered by low frequency currents. It utilizes two medium frequency currents (generated from two different circuits), passed through the tissues simultaneously. This interaction produces interference current (or what is called beat frequency). The exact frequency of the resultant beat frequency can be controlled by the input frequencies e.g., if one current was at 4000 HZ and its companion current at 3900 HZ, the resultant beat frequency would be at 100 HZ.
Physics of IF current:
The basic principle of Interferential Therapy is to produce low frequency electrical stimulation of the muscle and nerve (less than 250 Hz) without the associated unpleasant sensation of the low frequency stimulation. The medium frequency carrier currents penetrate the tissues with very little resistance. The resulting interference currents are in a range that allows effective stimulation of deeper tissues than other forms of electrical stimulation with relatively little patient discomfort.
Capacitive skin resistance is inversely proportional to the frequency of the current. An AC of 50 Hz encounters approximately 3000 ohms of resistance per 100 cm2 of skin. Increasing the frequency to 4000 Hz reduces capacitive skin resistance to approximately 40 ohms. So, low frequency currents usually face high degree of skin resistance and usually causes high degree of discomfort in the skin as it passes through.
In other words, the higher the stimulation frequency, the less the skin impedance and the less discomfort is experienced and vice versa. Consequently, IFS encounter less skin resistance and can pass to deeper tissues with using less current intensity than other low-frequency forms of stimulation.

Parameters of Interferential current:
− Waveform: biphasic symmetric balanced sine wave.
− Pulse duration: is ranging from 25 - 50 μsec.
− Frequency: the current frequency is about 4000 Hz but beat
frequency is dependent on the desired effect;
a. Sensory nerves: 90 – 100 Hz.
b. Motor nerves: 1 – 50 Hz.
c. Smooth muscle fibers: 0 – 10 Hz.
− Intensity: The current intensity is typically in the range of 0 - 100 mA which is dependent on the desired effect (sensory or motor stimulation).
− Frequency Sweep: accommodation is a characteristic feature of the excitable tissues (nerves and muscles) if they are stimulated using fixed frequency. Sweep (or gradually changing frequency) is often used to overcome this problem. The IF machine is set to automatically change the beat frequency.
Modes of sweep might be:
a. Classic ‘triangular’ sweep pattern: the machine gradually changes the frequency from base to top over a time period of 1 - 6 seconds. The machine is set to sweep from 90 to 130Hz employing a triangular sweep pattern.
b. Rectangular (or step) sweep pattern: the machine then ‘switches’ between the two preset specific frequencies suddenly rather than gradually.
c. Trapezoidal sweep pattern: is a combination of these two other patterns.
Sweep patterns; a) triangular pattern, b) rectangular pattern and c) trapezoidal pattern
Physiological effect:
The main clinical applications of IFT are: a. Painrelief.
b. Muscle stimulation.
c. Increasedlocalbloodflow.

d. Reduction of edema.
As IFT acts primarily on the excitable tissues, the major effects are those which are a direct result of such stimulation (i.e. pain relief and muscle stimulation). The other effects are more likely to be secondary consequences of these.
Pain Control:
High beat frequencies, about 100 Hz, when accompanied by sensory-level stimulation, activate the spinal gate, inhibiting the transmission of noxious impulses. Low beat frequencies of 2 to 10 Hz, applied at the motor level, should initiate the release of opiates and result in a narcotic-like pain reduction.
Muscle Stimulation:
IFT act in a similar way to faradic current but with much less uncomfortable.
a. Stimulationatlowfrequencyof1-30Hzwillresultina series of twitches (the most effective motor stimulation frequency is 10-25 Hz)
b. Stimulation at 50 Hz or more will result in a tetanic contraction.
c. Surged stimulation mode might be advantageous in reducing fatigue.
Blood flow:
Increased vasodilatation and local blood flow are noticed following interferential current due to:
a. Its effect on parasympathetic nerve fibers.
b. IFT increases local blood flow via muscle stimulation
which results in pumping action on the blood vessels. The 10-25 Hz frequency sweep appears to be the most beneficial in this regard.
Edema:
IFT may reduce edema through:
a. Producing local muscle contraction combined with, b. Local increase in blood circulation.
These two effects will encourage the reabsorption of tissue fluid and milking of the venous and lymphatic return through electrically evoked contraction. The beat frequency used is of a sweep of 10-15 HZ.

Indications:
− Pain relief.
− Facilitation of muscle contraction.
− Prevent muscle atrophy.
− Gynecological problems as stress incontinence and pelvic floor dysfunction.
− Improve circulation.
− Reduce edema. Contraindications:
− Unreliable patients.
− Lost or impaired sensation.
− Patient receiving deep X-ray therapy.
− Open infected and/or bleeding wound.
− Over the anterior neck region (carotid sinus).
− Near pacemakers.
Practical application
1- Preparation of the patient:
− Check the patient for the presence of any contra-indication.
− Apply sensory test on the patient.
− Explain the procedure to the patient.
− Put the patient in the most suitable and comfortable position.
2- Preparation of the device:
− Adjust equipment parameters.
− Apply the electrodes and conducting medium.
− Properly strap the electrodes in place.
3- Preparation of the treated part:
− The treated area must be exposed.
− Properly clean and dry the treated area.
− Remove any dust or grease on the skin.
4- Procedures:
− After securing the electrodes in the appropriate place, increase the intensity gradually till muscle contraction is clearly observed.
− Check the sensation and muscle contraction of the patient throughout the session, as accommodation may occur.

− Check skin regularly for signs of irritation.
− Session duration is 10-30 min – 3 times per week.
Types of electrodes:

1. Carbon-rubber electrodes: It should be enclosed in wet sponge or use conducting gel.


2. Pre gelled electrodes.


3. Suction electrodes: it is useful for larger body areas like the shoulder girdle, trunk, hip and knees.
   Carbon-rubber electrodes in different Suction electrodes shapes
   Electrodes placement:
   Quadripolar Technique
   The four electrodes are positioned around the painful area so that each channel runs perpendicular to the other and the current crosses at the midpoint. The interference effects branch off at 45-degree angles from the center of the treatment, in the shape of a four-leaf clover. Tissues within this area receive the maximal treatment effect.

Bipolar Electrode Placement
When IFS is applied using a bipolar technique, the mixing of the two channels occurs within the generator rather than in the tissues. Two channels are used within the generator, with a single output channel applied to the tissues.
Case study
Stress Incontinence
Incontinence is rather a symptom than a disease. A common neurological cause of incontinence is damage to cerebral cortex with damage to normal bladder control. Stress incontinence may also be due to weakness of pelvic floor muscles.
Correct placing of pads and electrodes:
Patient was positioned in semi-fowlers position. Interferential therapy was given using quadripolar method. Two electrodes were placed on the lower abdomen just above the outer half of the inguinal ligament and another two on the inner aspect of thigh near to the origin of adductor muscle. so as to produce good strong contraction of the pelvic floor.
Parameters of Interferential current:
Frequency of 1–100 Hz rhythmic is used. At low frequencies a twitch is produced, between 5 and 20 Hz a partial tetany and 30 to 100 Hz tetanic contraction occurs. Muscle contraction is produced with little sensory stimulation. It is claimed that the rapid return of the tone of pelvic floor muscles occurs when treated with interferential therapy due to stimulation of both voluntary and smooth muscle fibers. It has advantage over faradic

current stimulation that faradic currents can only stimulate voluntary components. Also, feel of current is much reduced in interferential therapy.