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Evidence-Based Article

What Does a TENS Unit Actually Do?

A practical, evidence-based guide for athletes and active individuals

A TENS unit — short for Transcutaneous Electrical Nerve Stimulation — is a small device that delivers low-voltage electrical currents through pads placed on the skin. Its primary purpose is pain modulation, offering a non-invasive way to reduce discomfort during training, recovery, or daily life.

Modern TENS units allow users to adjust frequency, pulse width, and intensity, making them adaptable for a wide range of musculoskeletal aches and pains. But what does the science actually say about how TENS works — and can it really help your muscles relax?

How Does a TENS Unit Work?

Although multiple mechanisms have been proposed, the most widely accepted explanation is the Gate Control Theory of Pain (Melzack & Wall, 1965):

Non-painful electrical stimulation “competes” with pain signals
This reduces the amount of pain information that reaches the brain
As a result, pain perception decreases

In short:
TENS doesn’t heal tissue — it changes how your nervous system processes pain.

This makes it useful for short-term pain reduction, especially after overuse, heavy training, or flare-ups of chronic discomfort.

Does TENS Help Muscles Relax?

Research suggests yes — but indirectly and situationally.

Evidence Highlights

Tension reduction: Taylor (1997) found that TENS can decrease passive muscle tension after repeated contractions or stretching.
Viscoelastic changes: Fukaya (2021) suggests TENS may temporarily alter muscle and connective tissue stiffness.
Flexibility: Maciel (2008) found TENS does not increase flexibility beyond stretching alone.

What this means in practice

TENS may help muscles feel less guarded or tight, especially when combined with:

stretching
light exercise
mobility work

But it is not a standalone tool for improving flexibility or long-term muscle relaxation.

How Should You Use TENS?

TENS units are widely available online or at pharmacies and do not require a prescription.

Best uses:

after intense training sessions
during flare-ups of chronic pain
on high-stress days with elevated soreness
as a temporary aid before mobility or rehab work

Usage guidelines:

sessions can provide relief that lasts minutes to hours
avoid running the device for over an hour without 10-minute breaks
use it as a supplement, not a primary treatment

TENS is best thought of as:
a short-term pain modulation tool, not a long-term fix.

For lasting improvement, it should be paired with strengthening, mobility, and graded activity that targets the underlying cause of pain.

Conclusion

A TENS unit can be a helpful tool for reducing pain, improving comfort, and easing muscle tension. Its effects are temporary, but when combined with exercise, stretching, or rehab programming, it can enhance recovery and improve daily function.

Understanding how TENS works — and where its limits are — helps athletes and active individuals use it safely and effectively.

< Recommendation by Our Experts>

✔ Combine TENS with active rehab
Use TENS alongside stretching, mobility, or strengthening to improve long-term outcomes.

✔ Use TENS as a short-term supplement
Apply it after hard training or stressful days, but avoid relying on it as your primary solution for pain.

✔ Learn your pain patterns
Understanding when and why your pain increases helps you apply TENS more effectively and build a broader recovery strategy.

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