Ultrasound machines are a treatment modality used by physical therapists that utilize high frequency sound waves. These sound waves are transmitted to the surrounding tissue and vasculature. They penetrate the muscles to cause deep tissue/muscle warming. (Passing through the body's tissues, these waves vibrate molecules. This causes friction and warmth as the sound passes through the tissue) This promotes tissue relaxation and therefore is useful in treating muscle tightness and spasms. The warming effect of the sound waves also cause vessel vasodilatation and increase circulation to the area that assists in healing.