What is Skin Impedance?

The word impedance comes from the Latin Impedire meaning to prevent, to stop from going on. That means skin impedance is the effective resistance of an electric circuit in the skin. let’s make it simple for you.

Imagine your body as a highway, and the electric current as a car trying to travel through it. The skin acts like a toll gate, with different frequencies of current facing different toll fees. Low-frequency currents have to pay a higher toll fee because they face more resistance from the skin’s outer layer, which can cause discomfort. But with interferential current therapy, two medium-frequency cars join forces and take a different route, bypassing the toll gate altogether and reducing the resistance they face. This makes the journey smoother and more comfortable for the cars, or in this case, for the patient receiving the therapy.

Equation for skin impedance

Skin impedance is inversely proportional to the frequency of the stimulation. It can be understood from this equation- Z = 1/2πƒC :

  • where- Z=impedence in ohms;
  •  ƒ=frequency;
  • C= capacitance of skin in microfarad.

In other words, the lower the stimulation frequency, the greater the impedance to the passage of the current and vice versa.

Production of beat frequency (low frequency) in IFT

When we apply two different medium-frequency currents to the body, with frequencies of 5,900 Hz and 6,000 Hz, they interact with each other in two ways: constructive interference and destructive interference.

production of beat frequency by constructive and destructive interference of two medium frequency wave

Constructive interference happens when the two currents merge together and create a bigger wave with a higher amplitude, or strength. This new wave oscillates, or vibrates, at a rate that equals the difference in frequency between the original two waves, which is called the beat frequency. Basically, the two currents combine to create a stronger wave that vibrates at a specific rate, and this can help to relieve certain medical conditions.