How Does It Work?
TENS, or transcutaneous electrical nerve stimulation, targets nerves. Electrodes deliver a comfortable tingling current that stimulates large sensory fibres, which reduces the transmission of pain signals carried by smaller fibres. At lower frequencies it also appears to trigger the release of the body own pain-modulating chemicals. You should feel a strong but pleasant buzz, never a muscle twitch.
NMES, or neuromuscular electrical stimulation, targets muscle. The current is strong enough to make the muscle contract whether or not you can activate it voluntarily. This matters after knee surgery or a period in a cast, when the quadriceps can become so inhibited that the brain struggles to switch it on at all, and no amount of willing it works.
IFC, interferential current, is a deeper-penetrating relative of TENS and is covered on its own page, since it is used differently and suits different presentations.
The distinction is not academic. Someone with chronic back pain needs TENS and should feel no contraction. Someone with a wasted quadriceps six weeks after surgery needs NMES and the contraction is the entire point. Using the wrong one wastes the session.
Types/Variations We Offer
Conventional high-frequency TENS: strong comfortable tingling, fast-acting relief that fades relatively quickly after switch-off.
Acupuncture-like low-frequency TENS: slower to take effect but often longer-lasting, felt as a rhythmic tapping.
NMES for muscle re-education: timed on-off cycles that make an inhibited muscle fire, typically at the quadriceps after knee surgery.
Russian stimulation: a higher-intensity NMES variant used for strengthening in athletic rehabilitation.
Conditions Treated
Advantages & Expected Benefits
Drug-free pain control that can be repeated as often as needed
NMES activates muscle that the brain is struggling to recruit after surgery or immobilisation
No sedation, no systemic side effects, and no interaction with medication
Home units can be prescribed with written settings once you have been assessed
Makes movement and exercise tolerable, which is where the lasting change comes from
Adjustable in the moment, so intensity always stays within your comfort
Potential Risks & Short-term Side Effects
Skin redness or irritation under the electrodes, usually from adhesive or from leaving pads in one spot too long
Muscle soreness after NMES, similar to the ache following unfamiliar exercise
Discomfort if intensity is raised too quickly
Reduced effect over time with a fixed TENS setting, which is why parameters are varied
Contra-Indications / Precautions
This treatment may not be suitable for individuals with:
- •Never over a cardiac pacemaker, implanted defibrillator or other implanted electronic device
- •Never over the abdomen or lower back during pregnancy
- •Never over the front of the neck, near the carotid sinus, or across the head
- •Never over areas of numb or altered sensation, where intensity cannot be judged safely
- •Never over active malignancy, an area of active infection, or broken skin
- •With caution in epilepsy, in severe cardiac disease, and in anyone unable to report sensation reliably
What to Expect in a Session
Screening: the contraindication list is checked directly with you before any electrode is placed, and this is not skipped for a repeat session.
Selection: your presentation determines whether TENS or NMES is used, and the two are not interchangeable.
Placement and titration: electrodes are positioned for your specific problem and intensity is raised slowly with you reporting throughout.
Treatment: usually twenty to thirty minutes, combined in the same visit with the manual therapy and exercise it is meant to enable.
Home protocol: if a unit is appropriate, you receive written settings, electrode placement diagrams, session duration and frequency, plus the safety rules.
Evidence & Clinical Guidelines
Evidence for TENS is mixed and honestly summarised here: reviews generally find small to moderate short-term pain reduction, with trial quality frequently low and effects that do not persist long after the unit is switched off.
NMES has stronger and more consistent support in a specific setting, quadriceps activation after knee surgery, where it helps address the muscle inhibition that limits early rehabilitation.
Neither is positioned as a treatment on its own. Both are used to reduce the barrier to movement so that exercise, which has the better evidence for lasting change, can actually be done.
Frequently Asked Questions
What is the difference between TENS and NMES?
TENS talks to nerves to reduce pain, and you should feel tingling with no muscle movement. NMES talks to muscle and deliberately makes it contract. Different problems, different machines settings, and using the wrong one achieves little.
Can I buy a TENS unit and use it myself?
You can, but get assessed first. The contraindications are absolute, particularly pacemakers, pregnancy and numb skin, and placement makes a large difference to whether it helps. We supply units with written settings after an assessment.
Will it fix my back pain?
No, and anyone saying otherwise is overselling it. It can reduce pain enough for you to move, exercise and sleep better. The exercise programme is what changes the underlying problem.
Why do I need electrical stimulation after knee surgery?
After surgery the quadriceps often becomes inhibited, meaning the brain cannot fully switch it on even when you try. NMES bypasses that and produces a contraction, which helps break the cycle of weakness and further inhibition.
Need More Information?
Our expert physiotherapists are here to answer any questions you may have about TENS and NMES.
Medically Reviewed
This content was reviewed for medical accuracy by Dr. Surabhi Bansal, BPT, MPT (Ortho) with 14+ years of clinical experience.
At Modern Physio, all medical content undergoes a thorough review process to ensure accuracy and alignment with current physiotherapy standards. Our content is created to educate and should not replace professional medical advice. Learn more about our review process.