Optimizing Neuromuscular Electrical Stimulation (NMES) in Rehabilitation: How, When, and Why?

Neuromuscular electrical stimulation, commonly referred to as NMES, is widely used in rehabilitation to strengthen muscles with reduced voluntary activation. It can be used in conservative treatments and before, during, or after surgery. Its main advantage is its ability to activate motor units even in the presence of pain, swelling, or neuromuscular inhibition. Many muscles can benefit from NMES, but the quadriceps is the most studied because of its essential functional role and its sensitivity to arthrogenic inhibition, a protective reflex that decreases muscle activation when a joint is irritated or painful (Watson, 2020). 

The Scientific Foundations of NMES: A Distinct Mechanism of Motor Recruitment 

NMES stimulates motor nerves directly through an electrical current applied to the skin. It bypasses voluntary control and triggers muscle contraction by depolarizing axons.
In normal physiology, small motor units are recruited first. With NMES, larger motor units are activated more quickly. These units are primarily type II fibres, which are faster and more powerful (Watson, 2020).
This reversed recruitment pattern allows NMES to produce an effective contraction even when voluntary activation is limited by pain, arthrogenic inhibition, surgery, or immobilization. It helps prevent loss of muscle quality and supports functional recovery when voluntary effort is restricted.
NMES also has motivational benefits. Patients who cannot voluntarily contract a muscle can observe a visible contraction produced by the device. This often reassures them and increases their engagement in rehabilitation. It can also reduce fear of movement and improve adherence to exercise programs. 

Optimal Timing of Use: From the Preoperative Period to Functional Recovery

The Preoperative Period 

Muscle prehabilitation is associated with better postoperative outcomes (Anderson et al., 2021). NMES helps maintain function when pain or instability limits voluntary exercise (Watson, 2020).
Although direct preoperative evidence is limited, early postoperative data suggest that regular stimulation preserves strength and reduces expected muscle loss (Watson, 2020). NMES therefore fits well into preoperative strengthening programs before ligament reconstruction or arthroplasty. 

The Early Postoperative Phase

NMES is most effective when introduced soon after surgery. Conley et al. (2021) recommend starting within the first two postoperative weeks, when muscle inhibition is at its greatest. Early use improves quadriceps activation and accelerates strength recovery.
A recent meta-analysis by Li et al. (2025) recommends beginning neuromuscular retraining within the first days after anterior cruciate ligament reconstruction. Early initiation is more effective than delayed application. This highlights the importance of early stimulation to optimize functional outcomes. 

The Intermediate Phase 

As pain decreases and mobility improves, NMES becomes a valuable adjunct to voluntary strengthening. It allows patients to reach contraction levels that they cannot achieve independently.
When combined with exercise, NMES can increase strength and reduce pain, particularly at frequencies between 50 and 75 Hz (Novak et al., 2020). Its use depends on the targeted goals, such as strength, proprioception, or endurance.

The Late Phase

When patients can perform high-intensity exercises, NMES is used to support specific rehabilitation goals. It may help correct persistent imbalances, address residual deficits, or assist in monitoring mechanical load during a return to meaningful or sport-specific activities.
Effects are generally more modest at this stage but remain useful. Peng et al. (2021) report moderate yet clinically relevant functional improvements after total knee arthroplasty. 

Conclusion: An Effective Modality When Applied at the Right Time

NMES is most effective when integrated at appropriate stages of rehabilitation. In the preoperative period, it helps preserve muscle mass and quality. Immediately after surgery, it reduces neuromuscular inhibition and facilitates early reactivation of the targeted muscle.
In later stages, it supports progressive strengthening, load monitoring, and optimization of muscle function. Regular use is essential for sustained benefits, much like a structured exercise program. Repetition and integration into self-management enhance its effectiveness.
Finally, the extensive evidence available on the quadriceps provides a solid reference for clinical application and can be adapted to other muscle groups with appropriate judgment. 

References 

Watson, T. (2020). Electrotherapy Evidence-Based Practice (13e éd.). Elsevier. 

Anderson, A. M., Comer, C., Smith, T. O., Drew, B. T., Pandit, H., Antcliff, D., Redmond, A. C., & McHugh, G. A. (2021). Consensus on pre-operative total knee replacement education and prehabilitation recommendations : A UK-based modified Delphi study. BMC Musculoskeletal Disorders, 22(1), 352. https://doi.org/10.1186/s12891-021-04160-5 

Conley, C. E. W., Mattacola, C. G., Jochimsen, K. N., Dressler, E. V., Lattermann, C., & Howard, J. S. (2021). A Comparison of Neuromuscular Electrical Stimulation Parameters for Postoperative Quadriceps Strength in Patients After Knee Surgery : A Systematic Review. Sports Health: A Multidisciplinary Approach, 13(2), 116‑127. https://doi.org/10.1177/1941738120964817 

Li, Z., Jin, L., Chen, Z., Shang, Z., Geng, Y., Tian, S., & Dong, J. (2025). Effects of Neuromuscular Electrical Stimulation on Quadriceps Femoris Muscle Strength and Knee Joint Function in Patients After ACL Surgery : A Systematic Review and Meta-analysis of Randomized Controlled Trials. Orthopaedic Journal of Sports Medicine, 13(1), 23259671241275071. https://doi.org/10.1177/23259671241275071 

Novak, S., Guerron, G., Zou, Z., Cheung, G., & Berteau, J.-P. (2020). New Guidelines for Electrical Stimulation Parameters in Adult Patients With Knee Osteoarthritis Based on a Systematic Review of the Current Literature. American Journal of Physical Medicine & Rehabilitation, 99(8), 682‑688. https://doi.org/10.1097/PHM.0000000000001409 

Peng, L., Wang, K., Zeng, Y., Wu, Y., Si, H., & Shen, B. (2021). Effect of Neuromuscular Electrical Stimulation After Total Knee Arthroplasty : A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Frontiers in Medicine, 8, 779019. https://doi.org/10.3389/fmed.2021.779019