Ultrasound Therapy has been used as a treatment modality for sports injuries by therapists over the last 50 years
Ultrasonic waves or sound waves of a high frequency that is not audible to the human ear are produced by means of mechanical vibration in the metal treatment head of the ultrasound machine. The treatment head is then moved over the surface of the skin in the region of the injury transmitting the energy into the tissues.
When sound waves come into contact with air it causes a dissipation of the waves, and so a special ultrasound gel is placed on the skin to ensure maximal contact between the treatment head and the surface of the skin and to provide a medium through with the sound waves can travel. Ultrasound can also be applied under water which is also a medium for ultrasound waves to travel through.
Ultrasound is a form of MECHANICAL energy, not electrical energy and therefore strictly speaking, not really electrotherapy at all but does fall into the Electro Physical Agents grouping. Mechanical vibration at increasing frequencies is known as sound energy. The normal human sound range is from 16Hz to something approaching 15-20,000 Hz (in children and young adults). Beyond this upper limit, the mechanical vibration is known as ULTRASOUND. The frequencies used in therapy are typically between 1.0 and 3.0 MHz (1MHz = 1 million cycles per second).