What's a TENS machine? Can it help my period pain or endometriosis?

You place two sticky pads on your tummy or lower back. Shutterstock^[9]

Here’s what we know so far

The exact mechanisms of how TENS works to reduce pain is still unclear. There are likely many different pathways^[10].

First, we need to first talk about different types of nerves. Nociceptors^[11] are nerves that send “danger” impulses about actual or potential tissue damage. Sensory nerves in your skin transmit information about things such as touch and pressure.

The gate control theory of pain^[12] says the spinal cord has “gates” that can be open or closed. When these gates are open, nerves can transmit these danger impulses up the spinal cord to the brain where they may be interpreted as “pain”. If these gates are closed, these impulses can’t reach the brain as easily.

TENS machines, especially at high frequency (greater than 50 pulses per second), tend to stimulate sensory nerves^[13] (the ones in your skin). These sensory nerves also send signals to your brain, but faster than the danger ones.

These sensory signals can close the “gates” at certain parts of the spinal cord. So if the TENS machine can stimulate enough of these sensory nerves in your skin, it will block at least some of these danger impulses from reaching the brain. The fewer danger impulses that reach the brain, the less pain you are likely to feel.

TENS machines may close the ‘gates’ at certain parts of the spinal cord so fewer ‘danger’ impulses reach the brain. Shutterstock^[14]

Then there’s the concept of endogenous opioids^[15] as pain relief. These are pain relieving chemicals the body makes itself.

TENS machines stimulate the release of these chemicals, with different types of endogenous opioids released depending on the frequency of stimulation^[16].

Read more: Explainer: what is pain and what is happening when we feel it?^[17]

So does TENS work?

For period pain

A systematic review^[18] in 2022 found four studies looking at TENS to manage primary dysmenorrhea (period pain that occurs without any physical changes in the pelvis).

There was a significant reduction in period pain when high-frequency TENS (more than 50 pulses per second) was compared to sham TENS (where the machine looks the same but doesn’t deliver a pulse).

This is in line with an older Cochrane review^[19] that found similar benefits.

Pain relieving effects only tend to last while the device is active.

For endometriosis

Endometriosis is where tissue similar to the lining of the uterus is found outside the uterus, commonly in the pelvis. There is only one^[20] study of TENS for pelvic pain due to endometriosis.

This study compared two types of TENS – one using a higher frequency for 20 minutes twice a day, and one using a lower frequency for 30 minutes once per week. Both types used pads placed on the tailbone, and women were told to make the pulses “strong, but comfortable”.

Both types improved pelvic pain, pain after sex, and quality of life, but not period pain. This was a very small study (11 women in each group) and there was no control or placebo group. So we need larger studies with a proper control group before we can be sure if TENS works for endometriosis pain.

Read more: I have painful periods, could it be endometriosis?^[21]

Is it safe?

Most studies^[22] report no side effects when the pads are used on the abdomen or lower spine.

However, if you turn up the intensity too high it can be uncomfortable^[23]. You could also get a rash from the adhesive on the pads.

Read more: First periods can come as a shock. 5 ways to support your kid when they get theirs^[24]

Which one to buy?

All TENS machines should allow you to change the intensity (how strong the pulse feels). Some also allow you to change the frequency (how often the pulses happen).

If you are going to use the device occasionally (less than 4-5 days per month) you may just need a device that allows you to change the intensity^[25].

To get the best relief, the machine should be turned up high enough so it delivers noticeable pulses, but is not painful. So you need to find your own comfort level.

For period pain, high frequency^[26] (more than 50 pulses per second) shows better results than low frequency (usually 2-5 pulses per second). So make sure the device you’re thinking of buying is either set to a high frequency or you can change the frequency.

Many people find it hard to manage period pain. So would TENS help? Shutterstock^[27]

For people with endometriosis, it’s a little more tricky. You’ll probably going to want to use the device more often than a few days a month.

Unfortunately, like with taking regular opioid painkillers, with regular TENS use people can become tolerant^[28] to its pain-relieving effect, which means it doesn’t work as well as it did when you first started using it.

One possible solution to tolerance is to use mixed-frequency TENS^[29] where both high and low frequencies are alternated. You can also slowly increase the intensity level over time.

TENS also doesn’t work well when people are regular opioid users^[30]. This is important as people with endometriosis are often using opioid medications^[31] to manage their pain. If you are using opioids regularly, high-frequency TENS is likely to be a better choice^[32].

Read more https://theconversation.com/whats-a-tens-machine-can-it-help-my-period-pain-or-endometriosis-201389

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