Electrotherapy devices use electronic circuits to produce non-lethal amounts of electrical energy, characterised as an electromagnetic field (EMF), in the body. These electromagnetic fields are in the form of frequencies or waves and the body acts like a conductor. When an electrical current flows in a conductor, an EMF is formed around the conductor. The voltage and the magnitude and type of current flowing determines the size and strength of the EM field. The EM field is also affected by the size, shape and type of conductor through which the electrical current flows. These are examples of different types of electromagnetic energy in the electromagnetic spectrum: X-rays, Ultraviolet light (UV), Visible light, Infrared light (IR), Microwaves and Radio-frequency radiation (RF).
The different parts of the electromagnetic spectrum are identified and classified according to their unique frequency or wavelength bands. The frequency and wavelength are inter-related, and as the frequency rises the wavelength gets shorter. The frequency is the rate at which the electromagnetic field goes through one complete oscillation (cycle) and is usually given in Hertz (Hz), where one Hz is one cycle per second. Electromagnetic fields are what are said in atomic theory to hold the atoms of matter. It is the force holding the electrons in orbit around the nucleus of an atom. It is possible to make an atom of something resonate with an EM field. If you increase the power of the resonance enough, heat will be generated, and if the power is increased enough, the atomic structure will break down.
http://perso.orange.es/ligiajohn/electrotherapy.htm
http://www.electrotherapymuseum.com/Museum18001900.htm
