What Is Neuromuscular Electrical Stimulation?
Neuromuscular electrical stimulation, commonly called NMES, is a physical therapy modality that uses controlled electrical impulses to stimulate nerves and produce a muscle contraction.
During NMES treatment, a physical therapist places electrodes over or near the targeted muscle. The electrical current stimulates the motor nerves that control the muscle, creating a contraction.
The goal is not simply to make a muscle contract. NMES can be incorporated into rehabilitation to help patients activate, strengthen, and retrain muscles that may be difficult to use effectively on their own.
NMES is commonly used alongside therapeutic exercise, strength training, mobility work, and functional rehabilitation.
Research has investigated NMES for a variety of situations, including postoperative rehabilitation, muscle weakness, neurological conditions, and recovery following periods of immobilization.
How Does NMES Work?
To understand NMES, it helps to understand how muscles normally contract.
When you voluntarily move a muscle, your nervous system sends electrical signals through motor nerves to the muscle fibers. These signals cause the muscle to contract.
NMES uses an external electrical stimulus to activate motor nerves and produce a similar contraction.
During a physical therapy session, the process may look like this:
- Electrodes are placed over the targeted muscle.
- The therapist selects appropriate stimulation parameters.
- The electrical current stimulates the motor nerve.
- The muscle contracts.
- The patient may perform a voluntary contraction at the same time.
- The stimulation is gradually adjusted based on the patient's response and rehabilitation goals.
The specific settings used can vary depending on the patient and the purpose of treatment. Factors can include stimulation intensity, frequency, pulse duration, electrode placement, treatment duration, and whether NMES is being used with active exercise.
This individualization is important because there is no single NMES protocol that is appropriate for every patient or condition.
What Is the Difference Between NMES and TENS?
NMES and TENS are both forms of electrical stimulation, but they are generally used for different purposes.
NMES is primarily designed to stimulate motor nerves and create muscle contractions. In physical therapy, it is commonly used to address muscle activation and strength.
TENS, or transcutaneous electrical nerve stimulation, is primarily used to influence pain perception through sensory nerve stimulation.
While both modalities use electrical currents delivered through electrodes, the intended physiological effect is different.
In simple terms:
NMES = muscle activation and contraction
TENS = primarily pain modulation
Your physical therapist can determine which type of electrical stimulation, if any, is appropriate based on your evaluation and goals.
What Are the Benefits of NMES in Physical Therapy?
NMES may be useful in rehabilitation for several reasons.
1. Improving Muscle Activation
After surgery, injury, pain, or immobilization, patients can sometimes have difficulty fully activating a muscle.
One common example is quadriceps weakness following knee surgery.
NMES can provide an external stimulus that helps produce a muscle contraction when voluntary activation is limited.
A 2025 systematic review and meta-analysis of randomized controlled trials found that adding NMES to rehabilitation following ACL surgery significantly improved quadriceps strength compared with standard rehabilitation alone at both short- and longer-term follow-ups.
2. Supporting Muscle Strength
NMES can be used as part of a strengthening program.
A systematic review and meta-analysis comparing NMES training with conventional strength training found that, when training volume was matched, NMES produced strength gains that were broadly similar to conventional strength training rather than clearly superior.
This is an important distinction.
NMES should not necessarily be viewed as a replacement for traditional strength training. Instead, it can be a supplemental tool when a patient needs additional assistance activating or loading a muscle.
3. Helping During Early Rehabilitation
Immediately following surgery or injury, patients may not always be able to tolerate traditional strengthening exercises at the intensity needed to effectively challenge a muscle.
NMES may provide a way to stimulate muscle contraction while the patient is gradually progressing toward more active exercise.
For example, after ACL reconstruction, quadriceps weakness can be a significant rehabilitation challenge. Research suggests that incorporating NMES into early rehabilitation can improve quadriceps strength compared with standard rehabilitation alone.
4. Helping Limit Muscle Loss
Periods of inactivity can contribute to muscle weakness and loss of muscle size.
NMES has therefore been studied in populations who are hospitalized or otherwise unable to participate fully in conventional exercise.
A systematic review of 42 studies involving 1,452 hospitalized adults found that NMES was associated with small improvements in muscle strength and walking performance and a moderate improvement in muscle size, although the researchers noted that many studies had unclear or high risk of bias.
5. Supporting Neurological Rehabilitation
NMES has also been studied in people with neurological conditions.
For example, research has examined NMES following spinal cord injury, where muscle activation and voluntary strength can be significantly affected.
A systematic review found some evidence that NMES may increase voluntary muscle strength in partially paralyzed muscles following spinal cord injury, although the evidence was not strong enough to establish NMES as superior to other strengthening strategies.
This highlights an important principle:
NMES may be useful, but the appropriate role of the modality depends on the patient's condition and rehabilitation goals.
Can NMES Build Muscle?
NMES can produce muscle contractions and can contribute to strength training.
However, it is important to avoid the idea that simply placing electrodes on a muscle automatically creates the same benefits as a comprehensive strength-training program.
Research in healthy adults has demonstrated strength gains following electrical stimulation, but studies have used widely different treatment parameters and protocols. A 2023 systematic review found that all 10 included studies reported significant strength gains, but researchers could not establish an optimal treatment duration, intensity, pulse, or frequency because of differences between protocols.
Another systematic review examining NMES combined with voluntary contractions found that adding NMES to exercise can improve strength, with many studies reporting greater improvements compared with voluntary exercise or passive NMES alone. However, results varied based on the stimulation and exercise protocols used.
For physical therapy, this supports using NMES strategically rather than treating it as a stand-alone solution.
NMES Combined With Exercise
One of the most useful applications of NMES may be combining electrical stimulation with voluntary exercise.
Instead of simply allowing the machine to create a passive contraction, a patient can actively contract the muscle while NMES assists the contraction.
This approach is sometimes referred to as NMES superimposed on voluntary contraction.
The idea is simple:
The electrical stimulation helps activate the muscle while the patient actively participates in the movement.
A 2023 systematic review found that this combined approach can produce meaningful improvements in muscle strength in healthy and orthopedic populations. The authors noted that the greatest improvements were often observed when NMES was combined with submaximal exercise involving both concentric and eccentric muscle actions.
This makes NMES particularly interesting as an adjunct to active rehabilitation.
What Does the Research Say About NMES After ACL Surgery?
ACL reconstruction is one of the more researched applications of NMES.
Following ACL surgery, quadriceps weakness can make it difficult for patients to regain normal strength and function.
A 2025 systematic review and meta-analysis evaluated 11 studies involving 202 patients and found that patients who received NMES alongside postoperative rehabilitation had greater improvements in quadriceps strength compared with standard physical therapy alone.
The researchers found benefits at both short-term and longer-term follow-ups. Earlier use of NMES was also associated with greater strength improvements in their subgroup analysis.
However, the same analysis did not find a significant difference in Lysholm knee scores in the studies that measured this outcome.
This is an important reminder that improving muscle strength does not automatically mean every aspect of function will improve to the same degree.
A successful rehabilitation program still needs to address strength, mobility, coordination, balance, movement quality, and progressive return to activity.
NMES and Knee Osteoarthritis
Researchers have also studied NMES in people with knee osteoarthritis.
A 2026 systematic review and meta-analysis specifically examined NMES combined with therapeutic exercise for people with knee osteoarthritis. The researchers evaluated outcomes including pain, physical function, and muscle strength.
This research adds to the growing body of evidence investigating whether electrical stimulation can provide additional benefits when paired with exercise-based rehabilitation.
For someone with knee osteoarthritis, the goal would not simply be to stimulate the quadriceps.
A comprehensive rehabilitation program may also include:
- Progressive strengthening
- Mobility exercises
- Balance training
- Gait training
- Functional movements
- Activity modification
- Education
- Gradual progression of exercise intensity
NMES can potentially be one component of that larger plan.
Does NMES Help With Pain?
NMES is primarily used to create muscle contractions rather than being a dedicated pain-treatment modality like TENS.
However, improving muscle activation and strength may indirectly help patients tolerate movement and exercise.
It is important not to promise that NMES will eliminate pain.
The appropriate goal depends on the patient's diagnosis and rehabilitation needs.
For some patients, the primary reason for using NMES may be muscle activation rather than pain relief.
Does NMES Hurt?
NMES should create a noticeable muscle contraction, but treatment should be adjusted to the patient's tolerance.
Patients may describe the sensation as:
- Tingling
- Pulsing
- Tightening
- Muscle contractions
- A strong but tolerable stimulation
The sensation can become stronger as the intensity is increased.
A physical therapist can adjust the settings based on the patient's response, the muscle being treated, and the goals of the session.
Is NMES the Same as "Getting a Workout"?
Not exactly.
NMES can create muscle contractions and contribute to strength development, but rehabilitation involves much more than producing a contraction.
Patients also need to develop the ability to:
- Control movement
- Coordinate muscles
- Bear weight
- Produce force
- Absorb force
- Maintain balance
- Perform functional movements
- Progress toward their specific activities
For that reason, NMES is generally most useful when it supports a broader rehabilitation program.
Who Might Benefit From NMES?
A physical therapist may consider NMES for patients experiencing:
- Muscle weakness
- Difficulty activating a muscle
- Postoperative weakness
- Muscle inhibition following injury
- Prolonged immobilization
- Certain neurological impairments
- Difficulty tolerating traditional strengthening early in rehabilitation
- Specific orthopedic rehabilitation needs
The decision to use NMES should be based on an individual evaluation rather than simply the presence of a particular diagnosis.
What Does Evidence-Based NMES Treatment Look Like?
Evidence-based NMES treatment is more than placing electrodes on a muscle and turning on a machine.
A physical therapist should consider:
The patient's diagnosis
Different conditions may require different treatment approaches.
The target muscle
Electrode placement and stimulation parameters need to be appropriate for the muscle being targeted.
Stimulation intensity
The intensity should be appropriate for the patient's goals and tolerance.
Treatment timing
NMES may be used during specific phases of rehabilitation or alongside particular exercises.
Active participation
When appropriate, combining NMES with voluntary contraction and therapeutic exercise may provide additional benefits.
Functional goals
The ultimate purpose of rehabilitation is improved function, not simply a stronger electrical contraction.
Is NMES Better Than Traditional Strength Training?
Current evidence does not suggest that NMES is universally superior to conventional strength training.
A 2022 systematic review and meta-analysis found that when training volume was matched, NMES and conventional strength training produced similar strength improvements.
This is actually useful information for patients.
NMES does not need to "beat" traditional exercise to have clinical value.
Its value may come from helping patients who cannot yet perform traditional exercise effectively or providing an additional stimulus during rehabilitation.
The Bottom Line
Neuromuscular electrical stimulation is a physical therapy modality that uses electrical impulses to stimulate nerves and create muscle contractions.
Research suggests that NMES can be useful for:
- Improving muscle activation
- Supporting strength development
- Addressing postoperative weakness
- Complementing therapeutic exercise
- Helping maintain muscle during periods of reduced activity
- Supporting certain neurological rehabilitation programs
The strongest evidence is not that NMES replaces exercise. Instead, research supports its use as an adjunct to an individualized rehabilitation program.
For example, research following ACL surgery suggests that adding NMES to standard rehabilitation can improve quadriceps strength, while broader research shows that NMES can produce strength gains that are comparable to conventional training under certain conditions.
Ultimately, the most effective physical therapy program is not about choosing between technology and exercise.
It is about knowing when and how to use each tool.
NMES at Core Performance Physical Therapy
At Core Performance Physical Therapy, technology can be incorporated into a comprehensive rehabilitation program based on each patient's individual needs and goals.
NMES may be used to help facilitate muscle activation and support strengthening while patients work through their active rehabilitation program.
The goal is not simply to create a muscle contraction. The goal is to help patients progress toward better movement, greater strength, improved function, and a return to the activities they enjoy.
If you are experiencing muscle weakness, recovering from surgery or injury, or having difficulty activating a muscle during rehabilitation, a physical therapy evaluation can help determine whether NMES may be an appropriate part of your treatment plan.
Frequently Asked Questions About NMES
What does NMES stand for?
NMES stands for neuromuscular electrical stimulation. It uses electrical impulses to stimulate motor nerves and create muscle contractions.
What is NMES used for in physical therapy?
NMES can be used to help with muscle activation, strengthening, postoperative rehabilitation, neurological rehabilitation, and maintaining muscle function during periods of reduced activity.
Is NMES safe?
NMES is commonly used as a physical therapy modality, but it is not appropriate for every patient. A physical therapist should determine whether electrical stimulation is appropriate based on the patient's medical history, condition, and treatment goals.
How long does an NMES treatment take?
Treatment time varies based on the muscle being treated, the patient's condition, stimulation parameters, and the overall rehabilitation plan.
Can NMES replace exercise?
Generally, no. NMES is best considered an adjunct to active rehabilitation. Research suggests that NMES can support strength development, but it does not eliminate the need for progressive exercise and functional training.
What is the difference between NMES and TENS?
NMES is designed primarily to stimulate motor nerves and create muscle contractions. TENS is primarily used to provide sensory stimulation for pain modulation.
Can NMES help after surgery?
NMES may be particularly useful following certain surgeries when muscle activation and strength are reduced. Research following ACL surgery has found improved quadriceps strength when NMES is added to standard rehabilitation.
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