Transcutaneous electrical nerve stimulation (TENS): Everything there is to know!

What is transcutaneous electrical nerve stimulation (TENS)?

Transcutaneous Electrical Nerve Stimulation (TENS) is a non-medicinal, non-invasive technique for relieving pain, which uses a low-voltage electrical current delivered through electrodes placed on the skin. This technique consists of sending mild electrical impulses to a specific nerve in order to alter neural transmission and prevent pain signal from reaching the brain. 

The device to which the electrodes are connected and which generates the current is called a TENS unit. You can be offered TENS therapy by a physical therapist, acupuncturist or other healthcare professional, if they think it may help you, or you can buy your own device over-the-counter. However, you should always ask for medical advice before using it. A TENS unit is a small battery-operated portable device, so you you can carry it around with you wherever you go.

How does transcutaneous electrical nerve stimulation (TENS) work? 

The TENS unit consists of a generator of electrical impulses linked to the electrodes positioned directly on the patient's skin. It works by means of mild electrical impulses that stimulate mechanisms responsible for pain sensation.

The action of the TENS machine is threefold:

• It blocks the transmission of pain signals to the brain, according to the gate control theory of pain. The TENS machine generates electrical impulses which activate nerve fibers of a larger caliber and that are faster than those used to convey pain signals. Thus, a tingling message is transmitted to the brain via the spinal cord and masks the pain signal for the duration of the session. The principle of gate control was described in 1965 by two Canadian scientists: Ronald Melzack (psychologist) and Patrick Wall (physiologist). 
  
• It stimulates the production of endorphins. Endorphins are analgesic substances naturally produced by the body. An increase in their quantity leads to a general analgesic effect.
  
• It improves blood circulation.
  

In hospitals or clinics, TENS is offered as an alternative to medication for chronic pain. It can also be used privately, at home.

The TENS unit uses a low-voltage electric current the intensity of which varies from 10 to 30 milliamps. The frequency of the pulses is between 40 and 150 Hertz (pulses per second).

Generally, there are 2 or 4 self-adhesive pads that are attached to the skin. They should be placed near the painful area or, depending on the case, along the path of a specific nerve or in other strategic locations.

The patient then adjusts the machine to find the intensity, frequency and duration of pulses that give maximum relief with minimum discomfort.

The settings of the device, as well as the duration and frequency of the treatment sessions, vary considerably from patient to patient.

In some cases, the effect is felt immediately. In other cases, it may take 30 minutes or an hour of treatment before pain is relieved.

Moreover, for some people, the effect may disappear as soon as the device is turned off, while for others, the relief lasts several hours or even days after the treatment is stopped.

For which health conditions is transcutaneous electrical nerve stimulation (TENS) recommended? 

TENS is a nonpharmacological, non-invasive therapy for chronic pain relief, which has no side effects.

In order to be considered chronic, the pain must:

• Be persistent or recurrent,
  
• Last longer than what is usual for this type of pain, especially if the pain has been going on for more than 3 months,
  
• Not respond adequately to drug treatments,
  
• Lead to a significant and progressive deterioration of the patient's functional and relational capacities in their daily life.
  
  

A TENS machine is used to relieve nerve, musculoskeletal or joint pain, often chronic, and of diverse origins, such as arthritis, back pain, migraine, foot pain, contractions during childbirth, etc. It can also be used as a complementary treatment to manage post-surgical traumatic pain problems.