Ultrasound is a machine that generates soundwaves which produce thermal and non-thermal effects in the body for therapeutic purposes.

The benefits of ultrasound were discovered in the early years after WWII when sonar systems were used to navigate submarines. During the process of experimenting with ultrasound, it was discovered that  sound waves cause a warming effect when absorbed by tissues with high densities of protein such as muscles, ligaments, and tendons. This heating effect increases local circulation and helps reduce pain and swelling from inflammation. The vibration that occurs from the waves causes a response within the cells that stimulates metabolism.