Medically Reviewed by Dr. Luis Alberto Vallejo
Interferential currents are medium frequency currents, alternating, rectified or not, with a frequency greater than 1000 Hz.
The classic interferential come from a carrier with alternating currents, sinusoidal medium frequency, in two electrical circuits that intersect, mix or interfere with each other.
Between both circuits, there must be a frequency difference of ± 250 Hz to obtain a new frequency equivalent to the difference between the originals due to the interference or whipping effect.
The advantage of the application of interferential currents is that through the use of medium frequency, it is sought to apply significant intensities without the patient manifesting discomfort to the passage of the current and there is a decrease in the impedance of the tissues to the passage of the electrical stimulus.
Phenomena of interferential currents
According to Lullabies, the negative half of the current cycle has a greater hyperpolarizing effect on the membrane potential than the positive half. After each alternating current cycle, the potential difference will decrease slightly approaching the threshold value.
After a certain number of cycles – effective time – the threshold value is reached, depolarization of the nerve fiber.
The higher the intensity the shorter the “effective time”.
This phenomenon constitutes the principle of summation.
Phenomenon explains the causes for which a muscle that is supplied with alternating current of medium frequency, contracts less and less and ends up not contracting.
If during stimulation one or more impulses coincide with the refractory period, repolarization of the nerve fiber within that period is more difficult or impossible.
The fatigue of the terminal motor plate increases as the frequency of indirect electrical stimulation rises.
To prevent this phenomenon it is necessary to interrupt the medium frequency current after each depolarization.
Modulation of interference currents
- Sinusoidal modulation: corresponds to the classical interferential.
- Foursquare modulation: used for muscle strengthening.
- Triangular modulation: used in the treatment of peripheral denervations.
– Amplitude modulation
- This is called the rhythmic increase and decrease of intensity, to allow repolarization.
- It implies that the frequency is fixed, only changes or modulations are being generated vertically
– AMF modulation
- Different AMFs produce different sensations in the patient so that the current can adapt to the sensitivity and pathology of the treated tissues.
- The choice of AMF is of great therapeutic importance.
- It can be adjusted as required, depending on the nature, stage, severity and location of the disorder.
- It is advisable to use a high AMF, 80-200HZ, in acute problems with severe pain and hypersensitivity, or if the patient feels fear towards electrical stimulation.
- The low AMF, less than 50 hz is used for subacute or chronic problems, producing muscle contractions.
Physiological Effects of Interferential Currents
- Transformation of electrical energy into thermal by the Joule effect, even if it is not perceived because it fails to stimulate the threshold of thermoreceptors.
- Production of smooth physiological phenomena.
- Increase in metabolism
- Liquefaction of the interstitial environment.
- Improvement of tropism.
- Sensitive, motor and energy effects
Indications of the Interferential currents
- Muscle enhancement
- Muscle relaxation.
- Muscle elongation
- Circulatory pumping.
- Analgesia in pains of chemical, mechanical and neuralgic origin.
- Tissue debridement, mainly at the beginning of collagen proliferation.
- Joint releases, in the stages of adhesion proliferation.
- Elimination of joint effusions (neither acute nor septic).
- Sympathetic dystrophy reflects.
- Intrinsic and intimate mobilization of the vertebral joints.
- Increase and improvement of local trophism by energy contribution.
- Recent tissue tears if applied with motor effect.
- Infectious processes
- Acute inflammatory processes
- Tumor processes
- Areas that may affect the gestation process.
- Pacemaker implants, intrauterine devices or any other electrical or metallic device installed intracorporeal.
- Do not invade heart with the electric field.
- Do not invade CNS or important neurovegetative centers.
- Beware of osteosynthesis or stent areas.