CoolTone is not a transcutaneous electrical nerve stimulation (TENS) Unit. A TENS Unit sends electronic stimulation through the skin. In order to impact the muscles, the device would have to be set to an uncomfortably high level which would make the skin feel like it’s being burned. This is why these devices have never been successful in true muscle stimulation and growth — they are better suited for treating pain. In contrast, the CoolTone bypasses the skin entirely focusing only on the muscles. This is why we are able to achieve “superhero contractions” comfortably.