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Can a TENS Unit Build or Tone Muscle?

With world-class athletes using stim machines to improve their performance, it begs the question from gym bunnies and couch potatoes, alike whether a TENS unit can build or tone muscles.

In an ideal world, where chocolate cake helps you lose weight, the answer to this question would be a resounding YES. But sadly, the utopian world where lying back effortlessly builds us a six-pack does not exist. And a TENS unit will neither build nor tone muscles. 


A transcutaneous electrical nerve stimulation (TENS) unit stimulates nerves and is a Godsend for many in terms of pain relief. But it’s not designed for anything other than this, for which it has proven to be effective in many clinical studies. The purpose of these units in lay terms is to confuse the nerves that are relaying pain signals to the brain, thus eliminating pain.

But, there is a catch. Most TENS devices also come with electrical muscle stimulation.

But what about EMS for building and toning muscles?

Many TENS units are combo units incorporating EMS (electro muscle stimulation), so can you just flick the switch and deliver electrical impulses to muscles to build and tone?

Well, yes, and no. EMS was first considered to be an effective muscle builder when Soviet scientists recorded improvements in performance of their athletes using EMS. And the FDA has approved companies including Slendertone for muscle toning claims.

EMS fires electrical impulses to muscles and forces muscles to contract and twitch involuntarily. It is used as a therapy for those that have been bed ridden and are suffering from muscle atrophy, so surely it can build muscles?

There is some truth to this, but EMS alone rarely produces significant increases in muscle size in muscle atrophy patients. EMS is effective for these patients in promoting healing and blood circulation to the muscles. It may improve muscle function, however, only resulted in an increase in muscle mass by around 1% after 5-6 weeks of treatment.

As for Slendertone and other such muscle toning belts, the FDA has come down on weight loss and six-pack claims regarding EMS for muscle toning and building. Instead the FDA has concluded that:

“Applying electrical current to muscles may cause muscles to contract. Stimulating muscles repeatedly with electricity may eventually result in muscles that are strengthened and toned to some extent but will not, based on currently available data, create a major change in your appearance without the addition of diet and regular exercise.”

So as ever, the real results come from diet and exercise. EMS can be used in conjunction with regular workouts to achieve top-level results. The main uses for EMS for athletes are to combine the treatment during workouts for maximum muscle building. They can also be used pre workouts to relax the muscles to avoid injury. And finally, EMS can be used as part of a post-workout program to help athletes recover from delayed onset muscle syndrome (DOMS), when they are too fatigued, stiff or achy to actively recover.

As for TENS, if you have an injury that causes you pain and is preventing you from exercising, then this therapy can help you get back to the gym and workout. This, in turn, will help build and tone muscles.