Jump to content

Transcutaneous Electrical Nerve Stimulation (TENS)

Original Editor - Professor Tim Watson Top Contributors - Abdallah Ahmed Mohamed, Admin, Kim Jackson, Rachael Lowe, Lucinda hampton, Joey Pease, Angeliki Chorti, Mohit Chand, WikiSysop, Uchechukwu Chukwuemeka, Vidya Acharya, Lauren Lopez, Erica Alexander and Khloud Shreif

Introduction

TENS is a form of electrical stimulation which mainly aims at symptomatic pain relief by exciting sensory nerves and thereby stimulating either the pain gate mechanism and/or the opioid system. [1] The different methods of applying TENS relate to these different physiological mechanisms. The effectiveness of TENS varies with the type of outcome being tartgeted at, but reports tend to imply that in some cases, when applied according to high standards od use, it can lead to better outcomes than a placebo intervention. [2] There is an extensive research base for TENS in both the clinical and laboratory settings and whilst this summary does not provide a full review of the literature, the key papers are referenced. It is worth noting that the term TENS could represent the use of ANY electrical stimulation using skin surface electrodes which has the intention of stimulating nerves. [3] In the clinical context, it is most commonly assumed to refer to the use of electrical stimulation with the specific intention of providing symptomatic pain relief. [4] If you do a literature search on the term TENS, do not be surprised if you come across a lot of ‘other’ types of stimulation which technically falls into this grouping.

The illustrations show a 2 channel TENS unit as it has 4 lead wires (Each channel has two lead wires) with electrode pads attached.

Digital TENS machines are becoming more widely available and extra features (like automated frequency sweeps and more complex stimulation patterns) are emerging, though there remains little clinical evidence for enhanced efficacy at the present time. Some of these devices do offer pre-programmed and/or automated treatment settings.

Mechanism of Action

The stimulation delivered by the TENS unit aims to excite the sensory nerves, activating specific natural pain relief mechanisms. These mechanisms primarily include the Pain Gate Mechanism and the Endogenous Opioid System. Different stimulation parameters are used to activate these two systems and their effectiveness may vary based on individual responses. [5]

Pain Gate Mechanism

The pain gate mechanism involves activation (excitation) of the A beta (Aβ) sensory fibres, which reduces the transmission of the noxious stimulus from the ‘C’ fibres, through the spinal cord to higher brain centres. This mechanism provides pain relief by essentially "closing the gate" to pain signals.

Frequency range: The Aβ fibres are optimally stimulated at a high frequency, typically 90 - 130 Hz (or pulses per second - pps).

Individual Variability: There is a no single frequency that works best for every patient, but this range appears to cover the majority of individuals. Patients should adjust the settings to find their optimal treatment frequency for maximum effectiveness.

Endogenous Opioid System

The other pain relief mechanism involves stimulating the A delta (Aδ) fibres which respond better to lower frequencies. This stimulations activate opioid mechanisms, leading to the release of endogenous opiates (E.G., enkephalins, endorphins) in the spinal cord that inhibits the transmission of noxious sensory signals.

Frequency Range: Aδ fibres are stimulated at a lower frequency, typically 2-10Hz.

Individual Variability As with the pain gate mechanism, there is no single "best" frequency. Patients should experiement within the range to find what works best for them. [6]

Burst Mode Stimulation

Burst mode stimulation combines the activation of both Aβ and Aδ fibres, offering a dual approach to pain relief.

In this instance, the higher frequency stimulation output (typically at about 100Hz) is interrupted (or burst) at the rate of about 2 - 3 bursts per second. When the machine is ‘on’, it will deliver pulses at the 100Hz rate, thereby activating the Aβ fibres and the pain gate mechanism, but by virtue of the rate of the burst, each burst will produce excitation in the Aδ fibres, therefore stimulating the opioid mechanisms. For some patients this is by far the most effective approach to pain relief, though as a sensation, numerous patients find it less acceptable than some other forms of TENS as there is more of a ‘grabbing’, ‘clawing’ type sensation and usually more by way of muscle twitching than with the high or low frequency modes.

The effects of a burst application of TENS on cervical range of motion (CROM) and pressure point sensitivity of latent myofascial trigger points (MTrPs) has been studied in a single-session, single-blind randomised trial. A 10-minute application of burst-type TENS may have a small effect on CROM and MTrPs. [7]Another study found that cryotherapy in combination with burst TENS may reduce pain, in contrast to combinations with conventional TENS. [8]

Burst mode stimulation has also been examined for its effects on postganglionic sympathetic vasoconstrictor fibers. Burst mode TENS applied at 25% above the motor threshold may result in a transient increase in calf blood flow, but has no effect on arterial pressure or skin temperature. [9]

Impedance of Current Flow

The amount of electrical current flowing through body tissues is influenced by the impedance of the pathway - this is a measure of how readily the body allows the current to pass.. Impedance in biological tissues consists of resistive (ohmic) properties and reactive elements, which can be capacitive or inductive. The inductive elements are negligible in body tissues, meaning they do not significantly affect current flow.[10]

Ohmic resistance refers to the resistance to direct current flow offered by tissues. Tissues that have a high water content, such as blood, muscle, and nerve, present less resistance, i.e., they have a lower ohmic resistance. Conversely, tissues such as bone and fat offer more resistance, and the skin's outer layer, the epidermis, has the highest resistance.[10]

However, in the context of Transcutaneous Electrical Nerve Stimulation (TENS) therapy, which typically involves high-frequency signals between 2 to 200 Hz, another type of resistance called capacitive reactance becomes particularly important.[11] This capacitive reactance pertains to the resistance offered by the capacitance of the tissue to the flow of alternating current. Capacitive reactance refers to the opposition that a capacitor offers to the flow of alternating current in an electric circuit. It impacts how tissues respond to varying frequencies of the electrical signal, particularly at higher frequencies.[10]

Therefore, to determine the effectiveness of TENS therapy, it is necessary to take into account both the resistive (ohmic) and capacitive elements of the skin and underlying tissues' overall impedance.[11]

Types of TENS

Conventional TENS(High) Acupuncture-like TENS(Low) Brief Intense TENS
Physiological Intervention To activate large diameter non-notious afferent to elicit segmental analgesia. To produce muscle twitch to activate small diameter motor affrent to elicit extra segmental analgesia. To activate small diameter noxious affrents to elicit peripheral nerve blockade and extrasegmental analgesia.
Clinical Teqnique Low intensity \High Frequency at site of pain to produce strong but comfrtable sensation. High intensity\Low frequency over muscle or Acupuncture points to produce strong but comfortable contraction. High intensity \High frequency to produce maximum parathesia
Duration of stimulation 30 min No more than 20 min no more than 5 min

[5]

[12]

Electrode Placement Technique

this is determined by the target muscle or muscle group either single or in relation to other muscles

  • Unilateral: Unilateral placement causes inflammation of one limb or half of a muscle pair.
  • Bilateral: It allow the stimulation of both limbs or both halves of a muscle Pair
  • Uni-polar: Only one of two essential leads and the electrode connected to it are placed over the target area affected by the stimulation This electrode is called treatment electrode.
  • Quadripolar: Involve the use of two sets of electrode each originating from its own channel. It may be considered the concurrent application of two bipolar circuit. This technique could be used with the stimulation of agonist and antagonist. Also, could be used in crossed pattern or for large flat area as back.

Contraindications

Absolute Contraindications

  • Patients with a pacemaker or implanted electronic devices. The electrical stimulation can interfere with device functionality.
  • Active skin lesions. Electrodes should not be placed over areas with dermatitis, eczema, open wounds, or infections.
  • Placement on the carotid sinus area. Stimulation over the anterior neck could cause adverse cardiovascular effects. [5]
  • Electrodes should not be placed over the eyes .

Relative Contraindications

  • Cognitive impairment where the patient does not comprehend the Physiotherapist's instructions or who are unable to co-operate. Patients who cannot understand and follow instructions safely should not use TENS unless appropriately supervised.
  • It has been suggested that application of the electrodes over the trunk, abdomen or pelvis during pregnancy is contraindicated due to the unknown consequences on foetal development and the potential risk of the currents inadvertently causing uterine contractions and inducing premature labour. [13] However, although not a first line treatment option, application of TENS around the trunk during pregnancy can be safely applied, following specific guidelines to treat musculoskeletal problems in pregnancy such as pelvic girdle pain [14] Additionally, TENS during labour for pain relief is both safe and effective.
  • Allergic reactions. Some patients may experience irritation or allergic responses to the electrodes, conductive gels, or adhesive tapes. Switching to hypoallergenic materials may resolve this issue.
  • Patients who have epilepsy should be treated at the discretion of the therapist in consultation with the appropriate medical practitioner, as there have been anecdotal reports of adverse outcomes, especially (but not exclusively) associated with treatments to the neck and upper thoracic areas.

Precautions

TENS, as a treatment technique, is noninvasive and has few side effects when compared with drug therapy. The most common complaint is an allergic type skin reaction (about 2-3% of patients) and this is almost always due to the material of the electrodes, the conductive gel or the tape employed to hold the electrodes in place. Most TENS applications are now made using self adhesive, pre gelled electrodes which have several advantages, including reduced cross infection risk, ease of application, lower allergy incidence rates and lower overall cost.

  • If there is abnormal skin sensation, the electrodes should preferably be positioned elsewhere to ensure effective stimulation
  • Avoid active epiphyseal regions in children (though there is no direct evidence of adverse effect)
  • The use of abdominal electrodes during labour may interfere with foetal monitoring equipment and is therefore best avoided.

The Evidence for TENS for Pain Control

A 2020 review suggests that the use of TENS has positive outcomes in the management of gynecologic procedures [15] [16]and conditions e.g. Primary Dysmenorrhea. [17][18]

A 2022 study set out to provide a critical review of the latest basic science and clinical evidence for TENS.[19] Key findings were:

  • Application of TENS at inadequate intensities is one of the primary factors attributed to conflicting reports of TENS efficacy. Using the strongest intensity that remains comfortable produces hypoalgesia in healthy subjects is imperative; lower intensities are ineffective. In addition to activation of greater numbers of sensory afferents, higher pulse amplitudes are proposed to activate deeper tissue afferents, allowing for greater analgesia. High intensity TENS decreases post-operative opioid requirements and negative opioid-side effects.
  • Both High Frequency(HF) and Low Frequency(LF) TENS been shown to provide analgesia specifically when applied at a strong, non-painful intensity. HF TENS may be more effective for people taking opioids.
  • Effective analgesia for chronic pain conditions may be limited by the development of tolerance to TENS if repeated application of either HF or LF TENS at the same frequency, intensity, and pulse duration is used daily.
  • Application of TENS electrodes at acupoint sites may increase analgesia and targeting the use of TENS during movement or required activity may provide the most benefit.
  • Emerging evidence suggests TENs may be helpful for people with spinal cord injury, and produce more significant analgesic effects when combined with exercise (HF & intensity). [20]
  • TENS may be effective in restoration of central pain modulation, a measure of central inhibition.[6]

Systematic reviews suggest that TENS, when applied at adequate intensities, is effective for postoperative symptoms (decrease in medication requirements), [21] fibromyalgia pain and disability, [22] osteoarthritis, painful diabetic neuropathy and some acute pain conditions.[23]

Effectiveness on Chronic Pain

There are nine reviews investigating TENS use in people with defined chronic pain or in people with chronic conditions associated with ongoing pain. One review investigating TENS for phantom or stump‐associated pain in people following amputation did not have included studies. For people with chronic pain, this overview offers very low quality evidence and cannot confidently make any statement regarding the effectiveness of TENS for people with chronic pain. The very low quality of all reviewed evidence means we have very limited confidence in any suggested estimate of effect for all outcomes and the true effect is likely to be different from that summarised here and within individual reviews.[24]

Future Directions

Future directions and advancements in clinical applications have been extensively discussed in a paper by Patel at al. [25] To address the limitations in existing technology, future research should focus on real-time optimisation of stimulation parameters, consistent therapy delivery, and improved accessibility. Furthermore, developing systems that enable remote monitoring and customisation of therapy protocols will promote the usability of TENS in diverse care settings. Research studies are needed using more rigorous study designs, standardised protocols, and meaningful patient-centered outcomes to fully realise the therapeutic potential of these modalities.[25] Last, an innovative system (NXTSTIM EcoAI™) is proposed as a significant advancement in delivering tailored, effective, and patient-friendly pain management and rehabilitation strategies.[25]

Resources

TENS on chronic Pain

TENS for constipation in children (systematic review)

TENS Unit

Tim Watson about TENS

References

  1. ↑ Maeda T, Yoshida H, Sasaki T, Oda A. Does transcutaneous electrical nerve stimulation (TENS) simultaneously combined with local heat and cold applications enhance pain relief compared with TENS alone in patients with knee osteoarthritis? J Phys Ther Sci. 2017 Oct;29(10):1860-1864.
  2. ↑ Sivaramakrishnan A, Solomon JM, Manikandan N. Comparison of transcutaneous electrical nerve stimulation (TENS) and functional electrical stimulation (FES) for spasticity in spinal cord injury - A pilot randomized cross-over trial. J Spinal Cord Med. 2018 Jul;41(4):397-406.
  3. ↑ Medical Policies. Transcutaneous Electrical Nerve Stimulation (TENS) - CAM 10109. Available from: https://www.myhealthtoolkitcapital.com/web/public/brands/medicalpolicy/external-policies/transcutaneous-electrical-nerve-stimulation-tens/ [accessed 28/1/2025]
  4. ↑ Johnson MI. Transcutaneous electrical nerve stimulation. In: Watson T, Nussbaum EL, eds. Electrophysical agents. 13 edn. Elsevier, 2020: 264–95
  5. ↑ 5.0 5.1 5.2 Johnson MI. Transcutaneous Electrical Nerve Stimulation: Mechanisms, Clinical Application and Evidence. Rev Pain. 2007 Aug;1(1):7-11.
  6. ↑ 6.0 6.1 Vance CG, Dailey DL, Rakel BA, Sluka KA. Using TENS for pain control: the state of the evidence. Pain management. 2014 May;4(3):197-209.
  7. ↑ Rodríguez-Fernández AL, Garrido-Santofimia V, Güeita-Rodríguez J, Fernández-de-Las-Peñas C. Effects of burst-type transcutaneous electrical nerve stimulation on cervical range of motion and latent myofascial trigger point pain sensitivity. Arch Phys Med Rehabil. 2011 Sep;92(9):1353-8.
  8. ↑ Macedo LB, Josué AM, Maia PH, Câmara AE, Brasileiro JS. Effect of burst TENS and conventional TENS combined with cryotherapy on pressure pain threshold: randomised, controlled, clinical trial. Physiotherapy. 2015 Jun;101(2):155-60.
  9. ↑ Sherry JE, Oehrlein KM, Hegge KS, Morgan BJ. Effect of burst-mode transcutaneous electrical nerve stimulation on peripheral vascular resistance. Phys Ther. 2001 Jun;81(6):1183-91.
  10. ↑ 10.0 10.1 10.2 Chizmadzhev YA, Indenbom AV, Kuzmin PI, Galichenko SV, Weaver JC, Potts RO. Electrical properties of skin at moderate voltages: contribution of appendageal macropores. Biophys J. 1998 Feb;74(2 Pt 1):843-56.
  11. ↑ 11.0 11.1 Gabriel S, Lau RW, Gabriel C. The dielectric properties of biological tissues: II. Measurements in the frequency range 10 Hz to 20 GHz. Phys Med Biol. 1996 Nov;41(11):2251-69.
  12. ↑ Ask Dr Jo. TENS. Available from: https://www.youtube.com/watch?v=TrFrcIzGF6E&feature=youtu.be (accessed 12.5.2019)
  13. ↑ Jones I, Johnson M. Transcutaneous electrical nerve stimulation. Continuing Education in Anaesthesia Critical Care & Pain. 2009; 9(4):130–5.
  14. ↑ Waller-Wise R. Transcutaneous Electrical Nerve Stimulation: An Overview. J Perinat Educ. 2022 Jan 1;31(1):49-57.
  15. ↑ Galtes J, Siretskiy R, Offield L, Esquenazi B. Efficacy of Transcutaneous Electrical Nerve Stimulation (TENS) for Management of Pain Associated With Hysteroscopy: A Systematic Review. Cureus. 2024 Oct 3;16(10):e70797.
  16. ↑ Günaydın S, Şen E, Yılmaz T, Kaya HD. Use of Transcutaneous Electrical Nerve Stimulation (TENS) in Labor Pain: An Integrative Review. Pain Manag Nurs. 2024 Nov 12:S1524-9042(24)00269-8.
  17. ↑ Elboim-Gabyzon M, Kalichman L. Transcutaneous Electrical Nerve Stimulation (TENS) for Primary Dysmenorrhea: An Overview. Int J Women's Health. 2020;12:1.
  18. ↑ Han S, Park KS, Lee H, Kim E, Zhu X, Lee JM, Suh HS. Transcutaneous electrical nerve stimulation (TENS) for pain control in women with primary dysmenorrhoea. Cochrane Database Syst Rev. 2024 Jul 22;7(7):CD013331.
  19. ↑ Vance CGT, Dailey DL, Chimenti RL, Van Gorp BJ, Crofford LJ, Sluka KA. Using TENS for Pain Control: Update on the State of the Evidence. Medicina (Kaunas). 2022 Sep 22;58(10):1332.
  20. ↑ de Espíndula Brehm T, Pang Bilby AS, Guizzo KZ, Marcolino AM, Kuriki HU, Barbosa RI. Effects of Transcutaneous Electrical Nerve Stimulation (TENS) During Functional Activities or Exercise: A Systematic Review. Musculoskeletal Care. 2024 Dec;22(4):e70020.
  21. ↑ Viderman D, Nabidollayeva F, Aubakirova M, Sadir N, Tapinova K, Tankacheyev R, Abdildin YG. The Impact of Transcutaneous Electrical Nerve Stimulation (TENS) on Acute Pain and Other Postoperative Outcomes: A Systematic Review with Meta-Analysis. J Clin Med. 2024 Jan 12;13(2):427.
  22. ↑ García-López H, Calle-Ortega F, García-Robles P, Del-Rey RR, Obrero-Gaitán E, Cortés-Pérez I. Effectiveness of transcutaneous electrical nerve stimulation improves pain intensity, disability and quality of life in patients with fibromyalgia syndrome: a systematic review with meta-analysis. Disabil Rehabil. 2024 Dec;46(26):6323-6333.
  23. ↑ Wu Y, Zhu F, Chen W, Zhang M. Effects of transcutaneous electrical nerve stimulation (TENS) in people with knee osteoarthritis: A systematic review and meta-analysis. Clin Rehabil. 2022 Apr;36(4):472-485.
  24. ↑ Gibson W, Wand BM, Meads C, Catley MJ, O'Connell NE. Transcutaneous electrical nerve stimulation (TENS) for chronic pain - an overview of Cochrane Reviews. Cochrane Database Syst Rev. 2019 Feb 19;2(2):CD011890.
  25. ↑ 25.0 25.1 25.2 Patel P, Green M, Tram J, Wang E, Murphy M, Abd-Elsayed AA, Chakravarthy K. Latest Advancements in Transcutaneous Electrical Nerve Stimulation (TENS) and Electronic Muscle Stimulation (EMS): Revisiting an Established Therapy with New Possibilities. J Pain Res. 2025 Jan 9;18:137-153.
Retrieved from "https://www.physio-pedia.com/w/index.php?title=Transcutaneous_Electrical_Nerve_Stimulation_(TENS)&oldid=365449"