Low-Intensity TENS & the Gate Control Theory
When using TENS at a low-intensity level, it is working through the Gate Control Theory. The Gate Control Theory suggests that there’s only a certain amount of stimuli that can get through to the brain. In other words, there is a ‘gate’ that only lets so much sensory information through. So, with TENS, you’re ‘flooding the brain’ with this sensory buzzing feeling so that the brain can’t really perceive the sensation from labour contractions as much.
High-Intensity TENS & the Diffuse Noxious Inhibitory Control Theory
When using your TENS on the high-intensity setting (with the intensity turned way up), researchers believe it relieves pain in a different way. The idea behind this other mechanism, which has a long name called Diffuse Noxious Inhibitory Control, is that by stimulating the body with another source of pain, you trigger the body to release its own natural pain relieving hormones called endorphins. In other words, you’re creating a slightly painful sensation to encourage your body to release those endorphins, which act kind of like your own morphine supply.
Researchers also conclude that TENS during labour works by decreasing anxiety, making you feel like you have more control over your labour, and by providing a distraction from labour contractions.
SOURCE: Evidence Based Birth www.evidencebasedbirth.com