Ultrasound is a deep heating treatment that is most effective in heating tissues of deep joints. It is helpful in improving the distensibility
of connective tissue, which facilitates stretching. Ultrasound machines utilize high or low frequency sound waves that are transmitted to the surrounding tissue and vasculature, penetrating the muscles to cause deep tissue and muscle warming. This promotes tissue relaxation and therefore is useful in treating muscle tightness and spasms. The warming effect of the sound waves also cause the blood vessels to dilate, which increases circulation to the areas needing healing.