TENS, which stands for transcutaneous electrical nerve stimulation, works by a machine sending out weak electronic impulses directly to the muscle cells. You place the TENS plates on the area you want to treat and, with the stimulation, the muscles begin to cramp. Pain is blocked by the body releasing its own pain-relieving hormones, called endorphins. The stimulation also causes circulation to start at a deep level, and contributes to the activation of the body’s self-healing process. TENS works on both instant and long-lasting pain with either low-frequency or high-frequency stimulation, depending on your choice. The pain relief can last for up to a few hours after a treatment is completed.