Part of the ORIEMS FIT Research Digest Series

At ORIEMS FIT, we share peer-reviewed research to help people better understand electrical muscle stimulation (EMS).
Our goal is not to make medical claims, but to explain what scientists are discovering — clearly and honestly — so readers can explore further on their own. Link to original study will be always provided at the end of each blog post for your deeper research and fact checks

This week, we highlight a study that challenges a common assumption about electrical stimulation.

Most people think electrical stimulation only affects the muscle being stimulated.
This research suggests something more interesting may be happening.

Research Question This Study Answers

Does electrical stimulation affect only the muscle being stimulated — or can it also influence muscles on the opposite side of the body?

This study explores that exact question.

Research at a Glance

Original Study Title

Direct Electrical Stimulation Impacts on Neuromuscular Junction Morphology on Both Stimulated and Unstimulated Contralateral Soleus

Study by

Researchers from Texas A&M University (USA)
and Karolinska Institutet (Sweden)

Published in

Journal of Cachexia, Sarcopenia and Muscle, 2023

Funding

Supported by the Swedish Research Council and the Erling-Persson Foundation

What Was This Study About?

The researchers studied direct electrical stimulation (DES) and how it affects neuromuscular junctions.

Neuromuscular junctions are the connection points where nerves communicate with muscles.
Healthy connections are important for normal muscle control and coordination.

In this study:

• Rats received electrical stimulation on the muscles of one leg

• The stimulation was applied over several days

• The other leg was not stimulated at all

The researchers then examined both legs.

What Did the Researchers Discover?

1. Changes Occurred in Both Legs

Even though only one leg was stimulated, changes were also seen in the opposite, unstimulated leg.

This is known as a cross-over effect.

2. Reduced Excessive Nerve Sprouting

In the stimulated muscle:

• Excess nerve growth was reduced by about 35%

In the unstimulated muscle:

• Similar reductions were observed

This suggests electrical stimulation helped maintain more balanced nerve-muscle connections.

3. Stronger and More Stable Connections

Electrical stimulation appeared to help:

• Preserve healthy nerve-muscle communication

• Prevent excessive structural changes that may interfere with muscle function

4. Body-Wide Signaling May Be Involved

The researchers found evidence that:

• Substances released from stimulated muscles entered the bloodstream

• These signals influenced muscles elsewhere in the body

This helps explain how effects appeared in muscles that were never stimulated directly.

5. Gene Activity Was Affected

More than 60 genes related to muscle and nerve health showed changes:

• In stimulated muscles

• And in unstimulated muscles

This suggests electrical stimulation may influence muscle biology at a deeper level than previously thought.

Why Is This Research Important?

Most electrical stimulation studies focus only on the muscle being treated.

This study shows:

• Electrical stimulation may have system-wide effects

• The body may respond as a connected system, not isolated parts

This challenges the idea that EMS works only locally.

What Does This Mean for EMS Users?

Based on this research, electrical stimulation may:

• Influence nerve–muscle connections beyond the stimulation site

• Support balanced muscle signaling across the body

• Affect muscles indirectly, not just directly

These findings help scientists better understand how EMS works, not just where it works.

Simplified Study Name

How Electrical Stimulation Affects Muscles on Both Sides of the Body

Link to the Original Research

You can access the original peer-reviewed study here:
👉 https://doi.org/10.1002/jcsm.13235

This link takes you to the publisher’s page, where full study details, methods, and data are available.

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ORIEMS FIT Research Digest Disclaimer

This article is for educational and informational purposes only.
It summarizes peer-reviewed research and does not provide medical advice.
Electrical muscle stimulation devices are intended for general wellness and fitness purposes only.