TENS vs EMS Machines: What's the Difference?

11 min read
TENS and EMS electrical stimulation machines compared

TENS and EMS machines both send electrical pulses through electrodes placed on the skin, but they have different main purposes.

TENS, or transcutaneous electrical nerve stimulation, is primarily used to reduce the feeling of pain. EMS, or electrical muscle stimulation, makes muscles contract and is mainly used for muscle activation and rehabilitation. In healthcare, this is often called neuromuscular electrical stimulation or NMES.

If you're looking for an electrical stimulation device for period cramps, TENS is the more relevant option. It may reduce primary period pain for some people, although responses vary and the research has limitations.

Key takeaways

  • TENS is mainly used for pain relief.
  • EMS or NMES is mainly used to activate muscles, often as part of rehabilitation.
  • TENS may reduce primary period pain for some people, but the evidence is low certainty.
  • EMS isn't designed specifically to relieve menstrual cramps.
  • Neither device treats the underlying cause of pain.
  • Electrical stimulation devices aren't suitable for everyone, so check the instructions for the specific device you're using.
  • Severe, worsening or unexplained pain deserves medical assessment rather than simply being masked with TENS.

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TENS vs EMS at a glance

Question TENS EMS / NMES
Main purpose Reduce the feeling of pain Make muscles contract
Typical sensation Tingling or buzzing, usually without a strong muscle contraction Noticeable muscle tightening or contraction
Common uses Pain management, including some types of period pain Muscle activation and rehabilitation
Period cramps May help some people Not designed specifically for menstrual pain relief
Strength of evidence Depends on the type of pain being treated Depends on the muscle, condition and rehabilitation program

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Some devices include both TENS and EMS modes. Having both modes doesn't make them interchangeable, so use each mode only for the purpose and electrode placement described in the device instructions.

How do TENS and EMS work?

How TENS works

A TENS machine sends small electrical currents through adhesive electrodes placed on the skin near the area of pain.

TENS is thought to reduce pain by stimulating nerves and changing the way pain signals are transmitted. It may also influence the body's own pain-modulating systems, including endorphins, although the exact mechanisms aren't completely understood.

TENS doesn't treat the underlying cause of pain.

The sensation should usually feel like tingling or buzzing rather than pain. Some people find electrical stimulation uncomfortable and skin irritation can occur underneath the electrodes.

How EMS works

EMS stimulates the nerves that control muscles, causing the targeted muscles to contract.

In rehabilitation this is often called neuromuscular electrical stimulation, or NMES.

Physiotherapists may use NMES as part of a rehabilitation program when muscle activation or strength has been reduced after injury, surgery or prolonged inactivity.

The goal is therefore different from TENS. TENS is aimed primarily at modifying pain sensation, while EMS is aimed at creating muscle contractions.

What are TENS and EMS used for?

TENS for pain

TENS is used for pain management in a range of settings, but the quality of evidence differs depending on the condition.

Australian health guidance lists uses including labour pain, some chronic pain, post-operative pain and palliative-care pain.

It's important not to assume that evidence for one type of pain automatically applies to another.

For example, a Cochrane overview of TENS for chronic pain found that the available evidence was too low in quality to confidently determine whether TENS was effective overall.

Period pain has its own research base, which we'll look at below.

EMS for muscle rehabilitation

EMS or NMES is commonly used in physiotherapy and rehabilitation to help activate muscles.

Research suggests that NMES can be useful as an addition to rehabilitation in some specific situations.

For example, a systematic review of people recovering from anterior cruciate ligament, or ACL, surgery found that adding NMES to standard rehabilitation improved quadriceps strength compared with rehabilitation alone.

That doesn't mean every consumer EMS machine will build muscle, improve sporting performance, increase circulation or speed recovery.

The benefit depends on the condition, device, settings, placement and overall rehabilitation program.

Is TENS useful for period pain?

TENS may reduce primary period pain for some people.

A 2024 Cochrane review included 20 randomised trials involving 585 participants aged 12 to 49.

Both high-frequency and low-frequency TENS were associated with lower pain scores compared with placebo TENS or no treatment.

On average, high-frequency TENS reduced pain scores by around 1.4 points and low-frequency TENS by around 2 points in the studies included in those comparisons.

Those numbers need some context. The studies varied considerably, were generally small and the reviewers rated the certainty of the evidence as low or very low.

The review also couldn't confidently determine whether high- or low-frequency TENS works better or how TENS compares with common pain-relief medicines.

Side effects were poorly reported.

This makes TENS a reasonable non-drug option to try for period cramps rather than a guaranteed pain-relief solution.

The research looked at primary dysmenorrhoea, which means period pain that isn't caused by another pelvic condition.

It doesn't show that TENS treats the underlying cause of conditions such as endometriosis or adenomyosis.

If you have severe or persistent period pain, read our guide to endometriosis and consider speaking with your GP.

You can also read our guide to managing period pain for other options.

TENS and EMS safety and precautions

Electrical stimulation devices have different intended uses, electrode positions and safety instructions, so always read the instructions supplied with your particular device.

TENS precautions

Australian health guidance advises against using TENS:

  • if you have a pacemaker or another implanted heart device
  • if you have epilepsy
  • for a new or unexplained pain unless your doctor has advised that it's safe
  • over an open wound or irritated skin
  • near your eyes
  • near a tumour or cancer
  • on your head
  • across your chest
  • on the front of your neck
  • while driving or operating machinery
  • in or around water, including in the bath, shower or pool

Can you use TENS during pregnancy?

If you're pregnant or there's a chance you could be pregnant, ask your GP, physiotherapist or midwife before using TENS.

TENS is sometimes used during labour, but that doesn't mean every TENS device or electrode position is appropriate throughout pregnancy.

Device instructions can differ, so avoid relying on a blanket rule such as simply avoiding the first trimester.

EMS precautions

Safety advice for EMS varies according to the device and its intended use.

Combined TENS and EMS devices commonly include precautions relating to implanted electronic devices, epilepsy and pregnancy.

Additional restrictions may apply depending on where the electrodes are placed and whether there is an existing muscle or joint injury.

If you're using EMS as part of rehabilitation, follow the program recommended by your physiotherapist and the instructions for the specific device.

Stop using either type of electrical stimulation if it causes pain, significant skin irritation or makes your symptoms worse.

When should you see a health professional?

TENS can change how pain feels, but it doesn't explain why the pain is happening.

See your GP if:

  • period pain regularly interferes with work, study, sleep or everyday activities
  • pain is becoming worse
  • you have new or unexplained pelvic pain
  • you have pain between periods
  • you experience pain during sex
  • you have pain when passing urine or opening your bowels
  • you have unusual bleeding or other new symptoms

Don't use TENS as a way of repeatedly masking severe pain while putting off assessment of its cause.

How to choose a TENS or EMS machine in Australia

Start by deciding what you're actually trying to achieve.

If your main goal is pain relief, TENS is the relevant function to look for.

If you're recovering from an injury or surgery and want electrical muscle stimulation as part of rehabilitation, ask your physiotherapist whether EMS or NMES is appropriate and how it should fit into your exercise program.

Some devices combine both TENS and EMS modes, which can be useful if you genuinely need both functions.

Things to check before buying

  • whether the device has TENS, EMS or both modes
  • its stated intended use
  • whether replacement electrode pads are readily available
  • battery or charging requirements
  • warranty and Australian support
  • the electrode-placement instructions
  • the safety warnings and contraindications
  • its Australian regulatory status where applicable

What does TGA or ARTG registration mean?

Medical devices supplied in Australia are regulated by the Therapeutic Goods Administration, or TGA.

Unless an exemption or exclusion applies, a medical device must be included in the Australian Register of Therapeutic Goods, or ARTG, before it can legally be supplied in Australia.

The regulatory requirements depend on the device's classification and intended purpose.

ARTG inclusion shouldn't be described simply as proof that a device has been โ€œTGA approvedโ€ to produce a particular result for every person.

When comparing devices, check the intended use, manufacturer's instructions, regulatory information and suitability for your individual circumstances.

Can you try before you buy?

Depending on where you live and why you need one, you may be able to hire a TENS or EMS machine from a physiotherapist, pain clinic or other healthcare provider.

This can be useful if you're not sure whether electrical stimulation suits you.

Period Shop stocks TENS devices, so we have a commercial interest in this topic. You can browse our TENS machines or visit our resources hub for more information.

Frequently asked questions

Can I use an EMS machine for period pain?

EMS is primarily designed to create muscle contractions rather than relieve menstrual pain. Research specifically supporting electrical stimulation for primary period pain relates to TENS, so if cramps are your main concern, TENS is the function to look for.

Can a machine have both TENS and EMS?

Yes. Some devices offer separate TENS and EMS programs. Use the appropriate mode for your purpose and follow the electrode-placement and intensity instructions for that mode.

Is TENS safe during pregnancy?

Don't assume that TENS is automatically safe or unsafe throughout pregnancy. Australian guidance recommends asking your physiotherapist, GP or midwife before using it. TENS is sometimes used during labour under appropriate guidance, but device instructions and safe electrode positions vary.

Can TENS treat endometriosis?

TENS may change how pain is experienced, but the current Cochrane evidence for menstrual pain relates to primary dysmenorrhoea. It doesn't show that TENS treats endometriosis itself or removes the cause of endometriosis-related pain.

Does a TENS machine work straight away?

Some people notice pain relief while TENS is running or shortly afterwards, while others notice little difference. The effect can also disappear after the device is switched off. Individual responses vary.

Does stronger TENS mean better pain relief?

Not necessarily. TENS should generally produce a strong but comfortable tingling sensation rather than pain. Use the settings recommended for your device and don't increase the intensity simply because you assume stronger stimulation must work better.

Can EMS build muscle without exercise?

EMS can produce muscle contractions and has useful roles in some rehabilitation programs, but that doesn't make it a replacement for voluntary exercise in a healthy person. Evidence from supervised rehabilitation can't automatically be applied to consumer devices marketed for general fitness or body toning.

Can I put TENS pads directly over my uterus?

Follow the electrode-placement instructions supplied with your particular device. Period-pain TENS devices are usually designed for placement on the skin of the lower abdomen or lower back, rather than according to the location of an internal organ.

What to remember

TENS and EMS use similar technology for different goals.

TENS is mainly used to modify the feeling of pain. EMS or NMES is mainly used to stimulate muscle contraction.

For period cramps, TENS has some supportive research and may be useful for some people, but it isn't guaranteed to work and it doesn't treat the underlying cause of pelvic pain.

Choose a device according to what you actually need it to do, follow its safety instructions and seek medical advice for severe, unexplained or persistent pain.

Related reading

Sources and further reading

This article provides general information and isn't a substitute for individual medical advice or the instructions supplied with your electrical stimulation device.