Ultrasound is high-pitched sound that people cannot hear. These high-pitched sound waves are sometimes used to treat muscle spasms and pain and to promote healing.
Ultrasound at higher intensities creates a deep heat that may help to ease muscle spasms, relax and warm muscles, and increase muscle elasticity before stretching and exercise.
Ultrasound may also act on the cells to promote healing. At lower intensities, ultrasound can have this healing effect without also heating the tissues.
Excessive use of either the heating or non-heating properties of ultrasound can damage tissues. Ultrasound is not generally used for children.
WebMD Medical Reference from Healthwise