TENS stands for 'Transcutaneous Electrical Nerve Stimulation', which means nerve stimulation through the skin. The device uses electrodes attached to the body to send weak electrical impulses to the nerve fibers. These impulses have a dual effect. Firstly, they help block pain perception by preventing pain signals from reaching the brain, and secondly, they support the production of endorphins, natural pain-relieving substances. Furthermore, they induce gentle muscle contractions that mimic a massage, thereby contributing to the relaxation of tense and stiff muscles, improving their blood circulation and regeneration.