Ultrasound waves are acoustic vibrations with frequencies greater than 16,000 Hz, of varying intensity, which are imperceptible to the human ear.
The main effects are an increase in: tissue metabolism and cellular activity; blood flow; capillary permeability; pain threshold; extensibility; elasticity of fibrous tissue.
Ultrasound treatment can be applied in two different ways: through skin contact with a fixed or mobile probe, and through immersion. In the former case, a layer of conductive gel is applied between the skin and the ultrasound probe, resulting in a more localized but more intense effect. Immersion is useful when treating small or irregular surfaces, or when the area is too sensitive for direct contact. The treatment area is immersed in a container or water with the probe positioned 2-3cm away from the body.