Want to improve muscle strength on one side? Stimulate both sides!

March 12, 2018

If you know someone who has suffered from chronic pain, you may have heard of TENS or transcutaneous electrical nerve stimulation. It’s a form of therapy that uses low-voltage electrical current, usually delivered by a small, battery-operated machine about the size of a pocket radio.

But did you know that the use of TENS as part of stroke rehabilitation is becoming popular?

Many studies validate the use TENS to improve muscle strength after a stroke. However, these studies looked into the effectiveness of TENS on the affected limb. None have looked at what happens when TENS is used on the unaffected arm or leg – until now.

Since other studies have deemed conventionally training involving both legs more beneficial than only training the affected leg, researchers from Hong Kong decided to look at if applying TENS to both legs could also increase training benefits. They wanted to compare the efficacy of bilateral TENS (applied on both affected and unaffected limbs) with unilateral TENS (applied only on the affected limb) when combined with task-oriented training (TOT).  

TENS in the research laboratory

Eighty patients, who had a stroke about five years ago, participated in the study. The average age of the subjects was 62 years.

Researchers assigned the patients to either the Bi-TENS or Uni-TENS group. All the patients in the study underwent 20 sessions of training over a 10-week period. Both legs of the patients in the Bi-TENS group received electrostimulation. The patients in Uni-TENS group received stimulation on one leg and a placebo, or fake, stimulation on the other leg. Both groups received TOT that included such exercises as stepping up and down, heel raising, holding a semi-squat position, balancing on a disk, walking across obstacles, standing up, and sitting down.

Researchers measured the patients’ leg strength at the end of the study. They also evaluated how long it took patients to complete the Timed-Up-and-Go test. In this test, the patient stands up from a chair, walks 3 meters, turns around, walks back and sits down again.

At the end of the study, researchers found out that the application of bilateral TENS combined with TOT was superior over the unilateral TENS with TOT.

The patients who received the bilateral TENS had earlier improvements compared to those who only had the unilateral TENS. The group also experienced an improvement in functional mobility as well as a gain in the strength of the muscles that lift their feet. The increase in muscle strength was still present three months after the training, but the functional improvements were not.

How does this apply to you?

If you’re interested in incorporating TENS therapy into your stroke rehabilitation, you’ll be relieved to know that it is not painful. However, some people do experience mild discomfort from the current. You can buy a TENS device for home use. You can adjust the wavelength frequencies on these devices so that they are comfortable for you. These devices can be found on Amazon. A highly-rated FDA-approved TENS unit costs about $26. As the study showed, it’s important to incorporate TENS treatment with structured or supervised physiotherapy.

This study only involved patients who had a good level of movement control. It also focused on specific types of leg paralyzes only. Future studies could tell us whether this is also effective for patients with more severe or different kind of strokes.

Will your insurance cover TENS?

Most insurance companies cover TENS, but many have requirements for approval. It’s best to talk with your insurance provider to find out.


The lead author of the study is Patrick W.H. Kwong, MSc from the Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong.

What you can do with this information

Editorial note:

TENS is increasingly popular in rehabilitation. This study shows that TENS application on both legs (including the unaffected leg) is more effective than just on the affected leg.

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