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What does a TENS unit do for muscles

What Does A TENS Unit Do For Muscles? (And What Doesn’t It Do?)

There are many questions surrounding the use of transcutaneous electrical nerve stimulation (TENS) units on muscles.

In short, TENS units aren’t considered to be the best and most effective tool for muscles but they can have their uses. In this article we delve into what a TENS unit does (and doesn’t do) for muscles.

Be aware, if you’re reading this there’s a chance that you’re thinking of an electric muscle stimulator (EMS) machine, a very similar looking device.

Confused About The Difference Between TENS And EMS?

Many people confuse TENS with electrical muscle stimulation (EMS). While TENS and EMS units can look almost identical, the two have completely different purposes so it’s imperative that you choose the correct type of device.


While TENS stimulates the sensory nerve endings – with the objective being to provide pain relief – EMS stimulates muscle motor nerves causing muscle contraction.

In some cases if the electrode pads are placed correctly on a muscle and used on a high setting, a TENS device may cause the muscles to twitch and contract, however this is not the intention of TENS therapy and not what the devices have been designed to do.

  • The programs on TENS machines are not created with the intention of causing muscle contractions, the way EMS programs are.

Like TechCare’s Plus 24, they tend to have names derived from massage techniques such as kneading, Swedish, and scraping, to name but a few.

In spite of that (and perhaps surprisingly) there is a body of evidence that supports the use of TENS for certain muscular conditions and situations. We’ll come onto that a little later in the article.

  • Programs on EMS units are designed to work the muscles in a particular way with specific contraction / relaxation times.
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Typically, electric muscle stimulators (PowerDot being a great example) come with programs that stimulate the muscles for both exercise preparation and recovery, along with programs for strength, resistance, and endurance.

Such programs on EMS units target either or both slow-twitch and fast-twitch muscle fibers, depending on their purpose.

Then there are combination units on the market, such as iReliev’s PlayMakar that offer both TENS and EMS capabilities:

Did You Know?

Electrical Muscle Stimulation (EMS) is also known by the names: NeuroMuscular Electrical Stimulation (NMES), electromyostimulation, e-stim, and stim.

Muscle Relaxation / Tight Muscles

A study carried out in 1997 investigated the effectiveness of electrotherapy on myofascial trigger points (knots) in patients’ shoulders (upper trapezius).

It looked at how 60 people (25 males and 35 females) responded to electrical nerve stimulation, electrical muscle stimulation, and placebo treatments.

  • The study concluded that EMS was more effective for the immediate release of muscle tightness than nerve stimulation.

EMS was found to improve the range of motion, which was measured by recording a neck side bend before and after the treatment.

But does a TENS unit relax muscles?

The mild electrical impulses from TENS can reduce the pain signals going to the brain, which may relieve pain and relax muscles.

In fact, a more recent (but very small) study with fifteen healthy young males found TENS combined with stretching to be effective in reducing pain and decreasing muscle hardness, leading to an increase in range of motion.

Muscle Knots

Perhaps surprisingly to some, the aforementioned study into the effectiveness of electrotherapy for muscle knots found electrical nerve stimulation to be more effective than electrical muscle stimulation for the immediate relief of myofascial trigger point pain.

  • The study concluded that nerve stimulation was significantly better for relieving pain caused by muscle knots.

Don’t confuse this with breaking up the knotted muscle tissue though:

From my own personal experience (if it’s not practical or possible to see a physical therapist or masseuse) I have found a powerful handheld electric massager to be more effective than either TENS or EMS for getting into muscle knots.

Muscle Spasms

Physical therapists and physicians often recommend their patients try a TENS unit for muscle spasms.

According to the NHS, TENS may be able to help reduce muscle spasms caused by conditions such as: arthritis, period pain, knee pain, back pain, and sports injuries.

That being said, solid evidence for treating general muscle spasms seems to be hard to come by, although studies have looked into TENS for specific conditions.

A big review carried out by the Center for Psychiatric Rehabilitation looked into spasticity after spinal cord injury (SCI).

The review referenced a study that used stimulation to a nerve in the leg which led to a decrease in muscle spasms, however it did go on to say further study is required to establish whether this would work in the same ways for people with different levels and completeness of injury.

Another noteworthy study used TENS to treat patients with muscle spasm after the lesion of upper motor neurone.

  • The authors reported a statistically significant decrease of muscles spasm in patients treated by TENS.
  • Stating that if longer stimulation is applied reducing of the muscle spasm is more pronounced.

Muscle Recovery

In 2007 researchers at Lagos State University College of Medicine conducted a study into the relief of Delayed-Onset Muscle Soreness (DOMS).

They examined how simple stretch exercises and trans-cutaneous electrical nerve stimulation (TENS) compared in the treatment of DOMS.

  • While TENS was shown to be effective in treating DOMS, it showed no superior benefits compared to stretching.
  • In fact stretching proved more effective in reducing muscle soreness – and compared to TENS – resulted in a greater range of motion.

A small but intriguing 2011 study looked into the effectiveness of three different between-inning recovery methods on baseball pitching performance.

The authors wanted to determine which of three forms of recovery were the most effective. They compared passive recovery, active recovery, and electromuscular stimulation (EMS).

The most notable finding was that EMS produced the highest reduction in blood lactate (lactic acid) levels. The other recovery methods had no significant effect on blood lactate.

(Reducing the amount of blood lactate post-workout is beneficial for the recovery of muscles).

  • The authors concluded the study by recommending that baseball pitchers consider employing EMS between innings as it may potentially lead to an increase in pitching performance.

Interestingly though other studies have found light exercise (such as swimming or jogging at a slow pace) to be more effective in blood lactate clearance.

An example of this being a comparison that pitted submaximal swimming against muscle stimulation after sprint swimming.

  • That particular piece of research concluded that submaximal swimming was most effective at lowering blood lactate.
  • However EMS also reduced blood lactate significantly better than resting passive recovery.

This therefore begs the question:

Why not just do light exercise for recovery and to clear blood lactate?

It’s not always practical. You may be physically and / or psychologically exhausted. It might be late at night. You may not have access to a pool.

Electric muscle stimulation can make your body produce the muscle contractions required to clear blood lactate and can be used at your own discretion, when and where you like.

The Verdict

There is research that supports the use of electrotherapy for muscles (both TENS and EMS modalities). However it’s not as conclusive as we’d like. More comprehensive studies and trials would be welcome in this field.

It might just be a case of seeing for yourself, depending on your objectives. If it is something you are considering there are many inexpensive machines for TENS and for EMS.

Alternatively, for dealing with tight or knotted muscles at home it might be worth looking at an electric massager or a foam roller.

Still not sure?

You can always stick with the more traditional methods such as stretching, light exercise, and massage!

Want to find out more?

There are plenty of posts on the site about TENS and EMS. Click on the links below to see them:

TENS posts

EMS posts

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One comment

  1. I have an elbow injury brought on by golfers elbow. At the moment I can not bend my elbow because of the injury. It is locked and I have been to see my GP and Surgeon. The Surgeon said that an operation is not required but I should see a physio. That hasn’t worked and my elbow is still the same or maybe getting worse.

    Will a stimulator work to free up the elbow.

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