5.2 Neuromuscular Electrical Stimulation (NMES) and Russian Stimulation

Neuromuscular Electrical Stimulation (NMES) and Russian Stimulation

Surface NMES usually activates intact peripheral motor axons to produce muscle contraction. The exercise goal determines the response to seek. Strengthening needs enough repeated force to load muscle. Functional electrical stimulation (FES) times stimulation to assist a task, such as clearing the foot in swing. Examine the voluntary movement, sensation, skin and relevant restrictions before choosing either application.

Voluntary and stimulated recruitment

During a gradually increasing voluntary contraction, lower-threshold motor units are generally recruited before higher-threshold units, consistent with Henneman's size principle. The nervous system adjusts both the number of active units and their discharge rates.

With conventional surface NMES over a muscle, the electric field preferentially reaches excitable axons near the electrodes. The order depends on axon geometry and proximity, electrode position and stimulation settings. Human tibialis anterior recordings showed reversal of relative recruitment in some motor unit pairs, with the majority preserving their relative order in that experiment. This does not support a fixed fast-twitch-first sequence. Directly excited units tend to discharge in time with the pulse train. Repeatedly activating the same units with little recovery can cause rapid force decline. Some stimulation configurations also recruit afferents and evoke reflex contributions to force.

Parameters for evoking a useful contraction

A randomized trial of quadriceps NMES after total knee arthroplasty (TKA) started treatment 48 hours after surgery. It used biphasic stimulation at 50 pulses/s with a 250 µs pulse duration as reported, 15 seconds on including a 3-second ramp-up, and 45 seconds off. Participants used 15 contractions twice daily at the maximum tolerated intensity. A 15:45 cycle is 1:3 and has a 25% contraction duty fraction including the ramp. This is a studied protocol. The 2026 APTA TKA guideline recommends starting quadriceps NMES in the early postoperative period, at least daily at the highest tolerable intensity, to improve quadriceps strength and performance-based outcomes. Apply the recommendation with surgical restrictions and equipment instructions.

Classical Russian stimulation

The classical Kots waveform is a 2,500 Hz sinusoidal alternating current delivered in 50 bursts per second with a 50% burst duty cycle. One burst period is 1/50 second, or 20 ms. Current is delivered for 10 ms and interrupted for 10 ms. The classical 10/50/10 treatment schedule describes a separate timescale: 10 seconds of stimulation and 50 seconds of rest repeated ten times. The contraction cycle in that schedule has an on:off ratio of 1:5 and a 16.7% on-time fraction. The carrier, burst pattern and contraction/rest schedule answer different dosing questions.

In an ideal capacitive element, reactance decreases as frequency increases. Skin–electrode impedance depends on several factors and does not show how deeply the motor response originates. In a human wrist-extensor comparison, classical Russian current produced less mean torque than the tested monophasic pulses, with less reported discomfort. A kilohertz carrier alone does not guarantee stronger, deeper or more comfortable contraction than other NMES waveforms.

Clinical application and screening

Knee surgery: Pain and effusion can contribute to arthrogenic muscle inhibition (AMI) and reduce voluntary quadriceps activation. NMES can add a contraction through intact peripheral motor axons while voluntary activation remains limited. For an unexpectedly large or worsening active lag, assess extensor mechanism integrity and possible postoperative complications. The Aspetar guideline recommends NMES in the very early phase after ACL reconstruction to support quadriceps activation or limit disuse atrophy. Continue active rehabilitation and respect the repair and positioning restrictions.

Stroke: For selected patients with foot drop, a gait sensor can trigger FES around swing to assist toe clearance when the peripheral nerve can respond. Compare walking quality, speed or safety with and without it, and consider an ankle-foot orthosis. Early after stroke, shoulder NMES can be considered to improve positioning and reduce subluxation in selected patients with minimal active movement. Assisted movement can also support upper limb task practice. Measure the intended functional or positioning outcome separately from pain.

Use the electrode and implant safety screening in the TENS section and the specific NMES device instructions. Confirm that the intended contraction is allowed by the surgical or injury plan. Inspect electrode contact and skin and monitor both force and symptoms. Defer when the site or patient falls under a labeling exclusion or when the contraction might compromise healing.

Clinical case

Twelve days after ACL reconstruction, a soccer player has full passive knee extension and an 18° active lag on straight leg raise. The treating team checks the incision, swelling, extensor mechanism and postoperative restrictions. When a supported isometric contraction is appropriate, two approved pads are placed on suitable skin over the quadriceps and adjusted to obtain a strong, tolerable contraction. The clinician measures its quality across repetitions, lengthens rest if force declines and pairs stimulation with active quadriceps practice. Reassess active lag, force and gait over visits. Progress loading as the clinical findings and surgical plan allow.