We recently reviewed various ways to reduce cramping pain associated with your period. One of the mechanisms discussed was Transcutaneous Electrical Nerve Stimulation (TENS). Although the name sounds complex, it can be broken down and understood relatively easily. The following article overviews what TENS is, how it works, and our favorite brands!
The word “transcutaneous” sounds overly complex and clinical, but if you break it down, it actually perfectly explains what is happening during TENS! Trans is latin for across, and cutaneous comes from the latin word cutin, meaning skin. When put together, trans-cutaneous means across the skin! Further, transcutaneous electrical nerve stimulation simply means applying an electrical stimulus across the skin to affect the nerves in some way.
How to use TENS?
TENS products typically consist of a device that outputs signals through multiple channels, ultimately delivering the stimulation through electrodes placed on the skin. The electrodes should be placed directly over the location of the pain, in order to provide local pain relief.
Now that we generally know what TENS is, let’s dive into what the best “dose” of it is. Start on a relatively low setting, and increase the intensity until you feel a non-painful sensation. It may take up to 30 minutes before you feel pain relief (1)!
There is no limit to the amount of time you can wear your TENS unit, but as time goes on you might feel that the sensation has worn off. Increasing the intensity should re-engage your brain and allow the pain relief to continue! After stopping TENS stimulation, the relief may disappear instantly, or might last up to 30 minutes (1).
Before going further, let’s distinguish between high frequency and low frequency TENS. High frequency refers to currents that are delivered at 50-100 Hz, while low frequency TENS uses currents at 2-4 Hz (2). As we will see, this is important when understanding the mechanism of pain relief.
High Frequency TENS
This is the more commonly used method, and the one that we recommend!
High frequency TENS works through exploitation of the “Gate Control Theory of Pain”, described by Ronald Melzack and Patrick Wall in 1965. In this revolutionary theory, Melzack and Wall proposed that pain is integrated in a specific portion of the spinal cord (3). This area, in this instance, serves as a gate that can be opened to allow the passage of pain signals; or it can be closed, eliminating the feeling of pain. The state of this gate ultimately depends on the size of the nerves that are carrying said signal. In pain perpetuating situations, small fibers are actively holding the gate open. Alternatively, larger fibers force the gate close, not allowing the pain signals to be carried on. Higher frequency TENS is thought to stimulate the larger diameter fibers that are responsible for closing the gate, limiting the passage of pain (3).
This is a simplified image of how the Gate Control Theory of Pain functions. For the full diagram, please view Melzack and Wall, 1965.
Additionally, high frequency TENS is thought to stimulate opioid receptors (which would cause pain relief) and simultaneously limit the concentration of pain-causing compounds in the spinal cord (4). Taken all together, high frequency TENS works through various pathways to limit pain.
Low Frequency TENS
Low frequency TENS operates through a slightly different pathway as compared to high frequency. Instead of influencing the nervous input, lower frequency TENS stimulates the release of opioids that are produced within the body. One important note regarding low-frequency TENS is that the stimulation itself is often painful. Through lower-frequency, but intense electrical signals, this method (through a complex pathway) causes acupuncture-like pain coupled with muscle twitches (2).
How long does TENS last?
As a whole, TENS offers relatively short-lasting pain relief. Lower frequency TENS is known to last longer, given that it causes the release of pain relieving compounds (4). Alternatively, higher-frequency TENS, as we mentioned earlier, stimulates fibers that “close” the pain gate. As such, when the stimulus is removed, the gate can “reopen,” allowing pain to pass through (1,3).
What are the risks of using TENS?
As a whole, TENS is very safe. There is a chance that the electrodes may cause irritation, but that is rare (4). The device is electrical and therefore should NOT get wet (1).
Because TENS uses electrical signals, people with heart conditions (including a pacemaker) are discouraged from using a TENS system (1). Additionally, the pads should not be placed close to the neck or head or around the heart. Lastly, those who are pregnant should consult their primary care physician before use (1). For an entire list of conditions that may place you at risk, please see this NHS flyer!
Ovira for period pain
Myoovi for period pain
The best way to measure if TENS is helping you, is to measure your pain over time. Whether it’s pain related to menstrual cramps, or something relating to an injury, tracking your pain can help you better understand your body. Daily check-ins with Wild.AI can allow you to track your pain levels and further explore your body! Download Wild.AI on the app or Google Store today!
- Patient Information: Transcutaneous Electrical Nerve Stimulation (TENS). West Suffolk NHS Foundation Trust, 19 Nov. 2021, chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.wsh.nhs.uk/CMS-Documents/Patient-leaflets/PainService/5287-2TranscutaneousElectricalNerveStimulation(TENS).pdf.
- Elboim-Gabyzon M, Kalichman L. Transcutaneous Electrical Nerve Stimulation (TENS) for Primary Dysmenorrhea: An Overview. Int J Womens Health. 2020 Jan 8;12:1-10. doi: 10.2147/IJWH.S220523. PMID: 32021488; PMCID: PMC6955615.
- Melzack, R., & Wall, P. D. (1965). Pain Mechanisms: A New Theory. Science, 150(3699), 971–979. http://www.jstor.org/stable/1717891
- Johnson M. Transcutaneous Electrical Nerve Stimulation: Mechanisms, Clinical Application and Evidence. Rev Pain. 2007 Aug;1(1):7-11. doi: 10.1177/204946370700100103. PMID: 26526976; PMCID: PMC4589923.
- Brown, Lesley, et al. “The Application of Transcutaneous Electrical Nerve Stimulation to Acupuncture Points (Acu-TENS) for Pain Relief: A Discussion of Efficacy and Potential Mechanisms.” Physical Therapy Reviews, vol. 14, no. 2, 2009, pp. 93–103, https://doi.org/10.1179/174328809X405964.