Abstract: Apparatus and method for the treatment and active massage of muscles, the apparatus comprising a generator arrangement providing a modulated alternating current with a medium-frequency carrier having a frequency comprised between 3000 Hz and 100,000 Hz, and an adjustable low modulating frequency of a fraction of 1 Hz, preferably both the carrier and the modulating currents being sinusoidal. Directly or after optional conversion to a polyphase current, a variable modulated current is supplied to electrodes placed about a body portion, e.g. a limb, whereby the current is made to flow transversally through the muscles, producing painless rhythmic muscular contractions.