Diathermy refers to the use of high-frequency electromagnetic waves (greater than 10 MHz) as therapeutic stimuli. Shortwave diathermy uses waves of 13, 27, or 45 MHz, while microthermy uses waves of up to 2450 MHz in frequency. Both forms of diathermy generate heat in deep muscle tissue, although microthermy is believed to be absorbed more by superficial fatty issue. The patient is placed between the electrodes, and the power level is adjusted until the patient reaches resonance (as determined by automated measurement systems) with a pre-established heating level. Each diathermy session lasts 10-30 minutes, depending on the size of the target area. The heat generated by diathermy improve blood circulation, relax muscular tension and promote drainage in the target areas.