A TENS unit sends mild electrical pulses through skin electrodes to interfere with pain signals and trigger the release of natural painkillers.
Principle
A TENS (transcutaneous electrical nerve stimulation) unit sends mild electrical pulses through electrodes on the skin to nearby nerves.
How it may reduce pain
- Gate control theory: the pulses compete with pain signals.
- Release of endorphins, the body’s natural pain relievers.
Uses
Back pain, arthritis, labor pain, menstrual cramps and neuropathy. Evidence is mixed. The effect is short-term.
Settings
High frequency (80 to 100 Hz) for quick relief, low frequency (2 to 5 Hz) for endorphin release.
How to use
Place pads around the painful area, start low and increase until a strong tingling occurs. Use 20 to 40 minutes.
Safety
Avoid with pacemakers, on broken skin, over the neck or head, in pregnancy (abdomen) and while driving or sleeping.
Talk to
A doctor or physical therapist.
Principle
A TENS unit (transcutaneous electrical nerve stimulation) is a small battery-powered device that sends low-voltage electrical pulses through electrodes on the skin. The pulses stimulate nerves to reduce pain. Typical devices deliver pulses at 1 to 150 hertz, with a pulse width of 50 to 250 microseconds, and the user adjusts intensity.
How it may reduce pain
- Gate control theory (Melzack and Wall, 1965): stimulating touch fibers (A-beta) at the skin may block pain signals carried by smaller fibers from reaching the brain.
- Endorphin release: low frequency (2 to 10 Hz) stimulation may trigger release of the body’s natural opioids.
- Other effects on nerve signaling.
The evidence is mixed. A Cochrane review found that results for chronic pain were uncertain, though some studies show benefit for labor pain, dysmenorrhea, fibromyalgia and arthritis. A 2019 review of reviews found positive evidence for several conditions with low to moderate quality.
Uses
Back pain, neck pain, arthritis, fibromyalgia, menstrual cramps, labor pain, nerve pain, tendonitis, sports injuries and post-surgical pain. It does not cure the cause of pain.
Settings
- Conventional (high frequency): 80 to 120 Hz, a comfortable tingling sensation, for quick relief of acute pain.
- Acupuncture-like (low frequency): 2 to 10 Hz, producing muscle twitches, for chronic pain.
- Intensity: strong but comfortable, not painful.
- Session time: 20 to 60 minutes, up to several times a day.
How to use
- Clean and dry the skin, and shave if needed.
- Place two to four electrodes around the painful area, at least an inch apart, not touching.
- Start with the unit off, and gradually raise the intensity.
- Use for 20 to 30 minutes, then remove.
- Replace electrode pads when they lose stickiness.
Safety
Do not use if you have a pacemaker or implanted defibrillator, are pregnant (except for labor under guidance), have epilepsy, or have heart disease without medical approval. Never place electrodes on the front of the neck, over the chest or head, over broken skin, near the eyes, or over areas with no sensation. Do not use while driving, sleeping or in water. Skin irritation is the main side effect.
Talk to
Consult a doctor or physical therapist before starting TENS, to confirm the cause of pain and settings. Units cost $20 to $200, and some are FDA-cleared for over-the-counter use.
Electrical settings and clinical evidence
TENS (transcutaneous electrical nerve stimulation) devices send low voltage pulses through skin electrodes. Typical settings are a frequency of 2 to 150 Hz and a pulse width of 50 to 250 microseconds, with high frequency (about 80 to 120 Hz) used for fast relief and low frequency (2 to 10 Hz) thought to promote endorphin release. The gate control theory proposes that stimulating touch nerves blocks pain signals in the spinal cord. A Cochrane review found evidence for TENS is of low quality, but it may help with some painful conditions, and it is considered safe. Place pads on clean skin around, not on, the painful area, at least an inch apart. Do not use TENS over the front of the neck, over the eyes, on broken skin, while driving or in water. People with pacemakers, defibrillators, epilepsy or pregnancy should consult a doctor first.
Based on data from the Cochrane Library and the FDA
