A TENS machine produces millions of tiny electrical impulses, which enter your body via electrodes placed on the skin near or over the painful region. These fast electrical impulses override the slower pain impulses and travel quickly along your nerves to your spinal cord and up to your brain. Your brain is immediately bombarded by millions of pleasant electrical impulses. Your pain signals continue to be sent to your brain but travel along much slower (smaller diameter) nerve fibres. Since your brain can only interpret a limited amount of information, the pain signals are easily outnumbered by the pleasant high-speed TENS stimulation. This is known as the Gate Control Theory.
The Gate Control Theory was initially proposed in 1965 by Melzack and Wall based on the fact that small diameter nerve fibres carry pain stimuli through a ‘gate mechanism’ but larger diameter nerve fibres going through the same gate can inhibit the transmission of the smaller nerves
carrying the pain signal.
Chemicals released (endorphins) as a response to the pain stimuli also influence whether the gate is open or closed for the brain to receive the pain signal. This led to the theory that the pain signals can be interfered with by stimulating the periphery of the pain site or the appropriate signalcarrying nerves at the spinal cord.
It is generally recognised that the ‘Pain Gate’ can be shut by stimulating nerves responsible for carrying the touch signal (mechanoreceptors) which enables the relief of pain through massage techniques, rubbing, and also the application of tens machines, wheat bags and ice packs.
Pain ‘Gating’ is very simply described by using the example of when you “bump your elbow”, and then rub it to ease the pain. When your elbow is bumped, pain messages travel to your brain. Here the messages are interpreted as “Pain”. Rubbing this same elbow vigorously will stimulate an
abundance of new “non-painful” messages to travel to the brain. Luckily, your brain can only interpret a limited amount of information. If the “rubbing” sensations outnumber the painful “bump” sensations, the brain will interpret the sensations as being from the painfree rubbing source rather than the painful bump. In other words, the rubbing sensations have ‘bombarded the gate’, so painful messages cannot get through.
We all know from personal experience, the faster we rub our bumped elbow, the better the results. Your TENS works in just the same way … it’s just rubs you via an electrical stimulation instead.
Plus, it doesn’t get as tired !
When using TENS to ‘close the gate’ we use Continuous (or Conventional) Tens Mode. Continuous TENS mode produces a gentle and pleasant ‘tingling’ under and between the electrodes. The ‘tingle’ sensation helps to block the pain by closing the ‘pain gate’ and slowing down the painful nerve signals – this produces analgesia (numbness) in the painful area that can last for a few hours.