Analgesia induced by transcutaneous or percutaneous neurostimulation. This fantastic device aims to relieve or block chronic and acute pain
The basis of TENS function is to generate sensations of pressure and movement that differ from the sensation of pain, so the nervous system stops perceiving it.
The choice of frequency is based on two different possibilities: low frequency (less than 10 Hz) and high frequency (greater than 50 Hz), with different physiological and therapeutic purposes.
These frequencies generate sensations of pressure and movement to modulate pain according to the “Gate Control” theory, which is based on the fact that the stimulation of large diameter afferent nerve fibres will inhibit the response produced by harmful ones; this occurs when interneurons located in the grey substance of the posterior pole of the spinal cord are activated. Hence, the need to use high intensities that reach deep tissues to ensure the effectiveness of TENS application.
In addition, at the spinal level, the “Gate Control” theory suggests that the involvement of inhibitory downstream supraspinal pathways would modulate spinal neurons.
However, the most recent available evidence confirms that in both cases endogenous opioid secretion is the main physiological mechanism responsible for analgesia produced by the application of TENS. There are three types of opioid receptors that are located peripherally, in the spinal cord and in supraspinal areas related to downward inhibition pathways. At each of these three levels, TENS has different physiological mechanisms of action.