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Functional Electrical Stimulation (FES) in Physiotherapy: Mechanism, Physics, Physiology, Indications, Contraindications, Procedure and Evidence
Introduction
Functional Electrical Stimulation (FES) is an advanced form of therapeutic electrical stimulation in which electrical impulses are used to activate muscles at an appropriate time so that they assist a purposeful functional movement.
This functional component is what distinguishes FES from general Electrical Muscle Stimulation (EMS) or Neuromuscular Electrical Stimulation (NMES).
With conventional NMES, the therapist may stimulate a muscle simply to produce contraction and improve strength.
With FES, the contraction is linked to a specific activity.
For example:
Electrical stimulation of the dorsiflexors during the swing phase of walking → ankle dorsiflexion → improved foot clearance
Other examples include:
stimulation of the quadriceps during standing
stimulation of ankle muscles during walking
stimulation of the upper-limb muscles during reaching
stimulation of muscles during cycling
stimulation of muscles to assist grasp and release
stimulation of lower-limb muscles during stepping
FES is particularly important in neurological rehabilitation because it can provide assistance when voluntary motor control is impaired but the peripheral neuromuscular system remains sufficiently excitable.
It has been investigated extensively in conditions such as:
stroke
spinal cord injury
multiple sclerosis
incomplete neurological lesions
foot drop
selected upper-limb motor impairments
Research suggests that FES can improve certain functional outcomes in selected patients, but the effects depend strongly on the condition, stimulation strategy, patient characteristics and the way FES is integrated into rehabilitation. A 2024 systematic review of stroke rehabilitation, for example, found positive effects on some measures of balance and gait velocity, while other walking tests showed no clear difference between FES and control interventions.
Therefore, FES should be understood as a functional rehabilitation tool, not simply as an electrical machine that makes muscles contract.
What Is Functional Electrical Stimulation?
Functional Electrical Stimulation is the application of electrical stimulation to produce muscle activity that contributes to a specific purposeful movement or task.
The central concept is:
Electrical stimulation + appropriate timing + purposeful movement = functional electrical stimulation
This timing component is extremely important.
Consider a person with foot drop after stroke.
If the peroneal nerve is stimulated while the patient is sitting, the ankle may dorsiflex.
But that alone is not necessarily FES.
If stimulation is synchronized with the swing phase of walking so that dorsiflexion occurs when the foot needs to clear the ground, the stimulation becomes functionally integrated.
Therefore:
NMES: "Make the muscle contract."
FES: "Make the muscle contract at the right time to help perform a task."
EMS, NMES and FES: What Is the Difference?
| Feature | EMS/NMES | FES |
|---|---|---|
| Primary objective | Muscle activation/strengthening | Functional movement |
| Muscle contraction | Desired | Desired |
| Timing with activity | Not always required | Central to treatment |
| Example | Quadriceps contraction while seated | Quadriceps stimulation during standing |
| Walking application | Possible | Common |
| Cycling application | Possible | Common |
| Neurological rehabilitation | Common | Particularly important |
| Main focus | Muscle | Task/function |
FES therefore builds upon the physiological principles of NMES but adds task-specific timing and functional purpose.
Mechanism of Action
The basic mechanism can be represented as:
Electrical pulse → peripheral nerve activation → action potential → muscle contraction → functional movement
However, FES involves an additional layer:
Electrical muscle activation + voluntary movement + sensory feedback + repeated task practice → motor learning and functional adaptation
Let's examine this step by step.
Step 1: Electrical stimulation is generated
The stimulator generates controlled electrical pulses.
The therapist selects parameters such as:
amplitude
pulse duration
frequency
ramp
duty cycle
stimulation timing
Step 2: Electrical current reaches the peripheral nerve
Electrodes are positioned so that the electrical field can activate an appropriate motor nerve or motor axons.
For foot-drop stimulation, for example, the common peroneal nerve or its branches may be targeted.
Step 3: The motor nerve is depolarized
When the electrical field reaches sufficient intensity, excitable nerve membranes are depolarized.
An action potential is produced.
Step 4: The muscle contracts
The action potential reaches the neuromuscular junction and activates the muscle fibers.
Depending on electrode placement and stimulation parameters, muscles can be activated to produce:
dorsiflexion
eversion
knee extension
hip flexion
grasp
elbow extension
cycling movement
Step 5: The contraction is synchronized with the task
This is the defining feature of FES.
A stimulation system may use:
a foot switch
heel switch
pressure sensor
accelerometer
motion sensor
trigger button
cycling position sensor
electronic gait sensor
to determine when stimulation should begin or stop.
Step 6: The stimulated movement contributes to function
The muscle contraction is not an isolated exercise.
It contributes to a meaningful task such as:
walking
stepping
standing
cycling
reaching
grasping
Physics Behind Functional Electrical Stimulation
The physics of FES is similar to NMES, but the timing and control system are particularly important.
1. Electrical potential
The stimulation device creates a voltage difference between electrodes.
This produces an electrical field within the tissues.
2. Current flow
Current flows through biological tissues between the electrodes.
The amount and distribution of current depend on:
electrode size
electrode position
tissue impedance
stimulation waveform
distance between electrodes
skin condition
3. Tissue impedance
Human tissue does not behave like a simple electrical resistor.
Electrical properties vary between:
skin
subcutaneous fat
muscle
nerve
bone
The skin, especially the outer stratum corneum, can present substantial impedance.
Good electrode contact therefore matters.
4. Electrode size
Electrode size affects current density.
A smaller electrode can produce a more concentrated electrical field beneath it.
This can increase selectivity but can also increase discomfort if current density becomes excessive.
5. Pulse amplitude
Amplitude determines the magnitude of the electrical stimulus.
The therapist generally increases intensity until the desired motor response occurs, while maintaining acceptable patient comfort.
6. Pulse duration
Pulse duration affects nerve excitability.
Longer pulses can alter the amount of current required to reach motor threshold.
7. Frequency
Frequency determines how rapidly stimulation pulses are delivered.
For functional movement, frequency must be high enough to generate a sufficiently smooth contraction but not unnecessarily high because excessive frequency can accelerate fatigue.
8. Duty cycle
FES can be:
intermittent
continuously triggered
phase-dependent
depending on the task.
For cycling, stimulation may be synchronized with different phases of the pedal cycle.
For walking, stimulation may occur only during selected parts of the gait cycle.
The Most Important Physics Concept: Timing
In conventional NMES, stimulation timing may be relatively simple.
In FES, timing can determine whether stimulation actually helps the movement.
Consider foot drop.
The patient needs dorsiflexion primarily during the swing phase.
If stimulation occurs:
too early → it may interfere with stance
too late → the foot may already have failed to clear the ground
for too long → it may produce unwanted movement
at the correct time → it can assist foot clearance
This is why FES systems may use sensors or switches to synchronize stimulation with movement.
Physiology: What Happens in the Body?
FES produces both immediate physiological effects and, with repeated training, potentially longer-term adaptations.
1. Motor activation
Electrical stimulation activates peripheral motor nerves.
This produces muscle contraction even when voluntary activation is incomplete.
2. Sensory feedback
Electrical stimulation also activates sensory afferent fibers.
The resulting sensory information can travel toward the central nervous system.
This means FES is not simply:
machine → muscle
It can also be:
machine → sensory system → central nervous system → motor-control system
This sensory input may contribute to motor learning and neuroplasticity, although the precise contribution varies by condition and FES protocol.
3. Repeated functional practice
One of the most important potential advantages of FES is that it can help a person perform repetitions of a movement that they cannot yet perform normally.
For example, a person with severe weakness may not be able to pedal a bicycle independently.
FES cycling can stimulate the appropriate muscles so that the person can participate in repeated cycling.
The patient therefore receives:
muscle activation
sensory feedback
movement repetition
cardiovascular activity
task-specific practice
4. Muscle strengthening
Repeated FES contractions can provide a training stimulus.
This can be particularly useful in people with neurological weakness or prolonged inactivity.
5. Cardiovascular and metabolic effects
When FES is applied to large muscle groups during cycling, rowing or stepping, it can increase metabolic activity and cardiovascular demand.
This is one reason FES cycling has been investigated extensively after spinal cord injury.
6. Potential reduction in spasticity
FES, particularly FES cycling, has been investigated for spasticity after spinal cord injury.
A 2021 systematic review and meta-analysis found that FES cycling reduced spasticity and also reported improvements in walking ability and lower-limb strength in the included studies.
However, more recent systematic-review work still describes the evidence as heterogeneous, with different stimulation and exercise protocols.
How Does an FES Machine Work?
An FES system can range from a simple stimulation unit with a manual trigger to a sophisticated computerized system with movement sensors.
1. Electrical stimulation generator
The generator creates the electrical pulses.
2. Electrodes
Electrodes deliver current to the skin and underlying nerve/muscle structures.
3. Control unit
The control system determines:
when stimulation starts
when it stops
which channel is activated
stimulation intensity
stimulation duration
timing relative to movement
4. Sensors
Advanced FES systems may use sensors to detect movement.
Examples include:
pressure sensors
accelerometers
gyroscopes
foot switches
joint-angle sensors
cycling position sensors
5. Triggering system
The trigger tells the stimulator when the appropriate movement phase has occurred.
For example:
Heel leaves the ground → stimulation begins → dorsiflexors contract
6. Multiple channels
Some systems can stimulate several muscles sequentially.
For example, a walking system may stimulate:
dorsiflexors
quadriceps
hamstrings
hip muscles
at different times in the gait cycle.
Indications
FES is primarily indicated when electrical stimulation can meaningfully contribute to a functional task.
1. Foot Drop After Stroke
This is one of the best-known clinical applications.
Weakness of ankle dorsiflexion can cause:
poor foot clearance
toe catching
compensatory hip flexion
altered gait
reduced walking confidence
FES can stimulate the peroneal nerve or dorsiflexor muscles during the appropriate phase of gait.
2. Stroke Rehabilitation
FES can be used for:
gait training
balance-related tasks
upper-limb function
cycling
task-specific motor practice
A 2024 systematic review and meta-analysis found that FES was the most commonly used electrical-stimulation approach among the included stroke studies. The review found positive effects on Berg Balance Scale scores and gait velocity, while 10-meter and 6-minute walking tests did not show a clear difference between FES and control groups.
3. Spinal Cord Injury
FES can be used for:
cycling
standing
stepping
gait training
muscle conditioning
cardiovascular conditioning
functional movement
A 2024 systematic review identified 37 clinical trials involving 192 people with spinal cord injury across different electrical stimulation approaches, including FES, with studies examining walking, standing, cycling and upper-limb function.
4. Multiple Sclerosis
FES has been used particularly for foot drop and walking limitations.
The objective is often to improve:
foot clearance
walking efficiency
gait safety
walking endurance
5. Incomplete Spinal Cord Injury
FES-assisted locomotor training is an area of ongoing research.
A 2026 systematic review and meta-analysis specifically examined FES-assisted locomotor training for walking outcomes after incomplete spinal cord injury, reflecting the continuing development of this rehabilitation approach.
6. FES Cycling
FES cycling can be used when voluntary lower-limb movement is limited.
The stimulation activates appropriate muscle groups to drive the pedals.
Potential goals include:
muscle conditioning
cardiovascular fitness
repeated lower-limb movement
spasticity management
strengthening
7. Upper-Limb Rehabilitation
FES can be used to assist:
reaching
grasping
opening the hand
releasing objects
elbow movement
The stimulation is timed with the desired task.
Contraindications and Precautions
FES requires careful screening.
Contraindications depend on the body region, equipment and patient's medical condition.
1. Implanted electronic devices
Particular caution is required in patients with:
pacemakers
implantable cardioverter-defibrillators
neurostimulators
other implanted electronic systems
Electrical stimulation can potentially interfere with some implanted devices.
2. Anterior neck/carotid sinus
Routine stimulation over the anterior neck or carotid sinus should be avoided.
3. Across the chest
Electrical stimulation should not routinely be applied in a configuration that directs current across the chest.
4. Pregnancy
Routine FES over the abdomen and pelvis is generally avoided during pregnancy.
5. Active thrombosis
Strong electrically induced muscle contractions may be inappropriate over an area of known acute thrombosis.
6. Active bleeding
Strong muscle contractions may be contraindicated in an actively bleeding region.
7. Significant sensory impairment
Patients with poor sensation may not recognize excessive stimulation or skin irritation.
8. Broken or infected skin
Electrodes should not normally be placed over:
open wounds
severe dermatitis
active skin infection
significant skin breakdown
unless a specific specialist protocol supports it.
9. Malignancy
Routine stimulation directly over known malignant tissue should generally be avoided unless specifically indicated in a specialist setting.
10. Severe peripheral nerve injury
Conventional FES depends on an electrically excitable peripheral motor pathway.
If the relevant motor nerve is completely denervated and cannot be activated by surface stimulation, conventional FES may not produce the desired movement.
11. Uncontrolled seizure disorders
Stimulation near the head and neck requires particular caution in people with epilepsy.
How FES Is Applied — Procedure
Step 1: Identify the functional problem
The therapist should begin with the movement problem rather than the machine.
For example:
Problem: foot drop during walking.
Goal: improve foot clearance during swing.
Step 2: Assess the neuromuscular system
The therapist evaluates:
muscle strength
active range of motion
passive range of motion
motor control
sensation
spasticity
peripheral nerve integrity
joint stability
gait pattern
skin condition
Step 3: Establish the functional goal
Examples:
improve foot clearance
assist standing
improve cycling
facilitate grasp
assist reaching
increase walking speed
improve walking endurance
Step 4: Select electrode placement
Electrodes are positioned over:
a motor nerve
motor point
muscle belly
depending on the system and therapeutic objective.
Step 5: Test stimulation
The therapist gradually increases intensity to determine whether the desired movement can be produced.
For example:
Peroneal stimulation → dorsiflexion/eversion
The therapist observes whether the movement is appropriate.
Step 6: Adjust stimulation parameters
The therapist selects:
amplitude
pulse duration
frequency
ramp
stimulation duration
timing
Step 7: Synchronize stimulation with the task
This is the defining stage of FES.
For gait:
stimulation → appropriate gait phase
For cycling:
stimulation → appropriate pedal phase
For reaching:
stimulation → movement initiation or desired movement phase
Step 8: Practice the functional movement
The patient performs the task repeatedly.
The therapist observes:
movement quality
timing
compensations
safety
fatigue
patient tolerance
Step 9: Progress the task
As the patient improves, the therapist may modify:
stimulation intensity
timing
walking speed
resistance
task complexity
duration
amount of voluntary effort
Step 10: Gradually encourage voluntary contribution
The long-term objective should generally not be dependence on stimulation.
The patient should be encouraged to use their own voluntary motor control whenever possible.
FES can provide assistance while the nervous system practices the movement.
Example: FES for Foot Drop
Consider a patient after stroke.
The patient has:
ankle dorsiflexion weakness
toe drag
reduced foot clearance
compensatory hip hiking
The therapist places electrodes to stimulate the appropriate dorsiflexor/peroneal pathway.
A gait sensor detects the appropriate phase.
During swing:
Sensor detects gait phase → stimulation delivered → dorsiflexors contract → ankle dorsiflexes → foot clears ground
This is a classic example of FES.
The stimulation is not merely strengthening the muscle.
It is helping the muscle participate in walking.
FES for Cycling
FES cycling uses electrical stimulation to activate muscles in a coordinated pattern that drives a stationary bicycle.
The system can stimulate different muscle groups at appropriate points in the pedal cycle.
Possible targets include:
quadriceps
hamstrings
gluteal muscles
calf muscles
The patient may therefore achieve repeated lower-limb movement even with very limited voluntary activation.
FES for Spasticity
FES cycling has been studied as an intervention for spasticity following spinal cord injury.
A systematic review and meta-analysis found significant reductions in spasticity in the included studies and reported improvements in walking ability and lower-limb strength. The review's subgroup analysis suggested that studies using more than 20 sessions showed a significant reduction in spasticity, although the relationship between the exact number of sessions and effect was not linear.
A newer 2025 systematic review identified 16 studies involving 203 participants and found that 10 studies reported reduced spasticity following FES cycling.
These results are encouraging but should not be interpreted as proof that FES will reduce spasticity in every patient.
Treatment Parameters and Dosage
There is no universal FES prescription.
The appropriate dose depends on:
diagnosis
functional goal
muscle condition
nerve integrity
stimulation system
task
patient tolerance
stage of rehabilitation
Important parameters include:
Frequency
Determines the temporal characteristics of muscle contraction.
Pulse duration
Influences motor-nerve recruitment and stimulation comfort.
Amplitude
Determines stimulation intensity.
Timing
Extremely important in FES.
Ramp
Controls gradual onset and offset of stimulation.
Duration
Determines total training volume.
Number of sessions
Depends on the rehabilitation goal and research protocol.
The literature contains considerable variation in these parameters, and optimal dosing has not been firmly established for all applications.
Research Evidence
FES After Stroke
Stroke is one of the most extensively studied areas.
A systematic review and meta-analysis published in 2015 included 18 trials and found that FES produced a moderate improvement in activity compared with no or placebo intervention and also showed a moderate effect compared with training alone. The review found a small improvement in walking speed.
However, more recent reviews demonstrate that results depend on the exact intervention and outcome.
A 2024 review of 20 studies found positive effects for balance and gait velocity but not consistently for all walking measures.
This is an important lesson:
FES may improve some functional outcomes without improving every measure of walking.
FES for Post-Stroke Foot Drop
A major clinical application is peroneal nerve stimulation.
A systematic review and meta-analysis of FES for post-stroke foot drop found that FES combined with physiotherapy improved gait speed compared with physiotherapy alone or control interventions.
Another meta-analysis involving 11 randomized trials and 1,135 participants found that both ankle-foot orthoses and FES significantly increased walking speed compared with no intervention/placebo. The review found no significant difference between FES and ankle-foot orthoses for walking speed or balance.
This is clinically important.
It means FES should not automatically be presented as "better than an AFO."
Both can be legitimate rehabilitation options, and the choice depends on:
gait pattern
motor control
patient preference
skin tolerance
cognitive ability
footwear
spasticity
device access
functional goals
FES Cycling After Spinal Cord Injury
FES cycling is another major area of research.
A systematic review examining FES cycling after spinal cord injury included 92 studies involving 999 adults. The evidence covered health and fitness outcomes across a broad range of injury levels and completeness.
This large evidence base demonstrates that FES cycling is an established area of rehabilitation research.
However, the presence of many studies does not mean every outcome is definitively established.
The quality and design of studies vary considerably.
Recent Evidence on FES Cycling After Stroke
A 2026 systematic review and meta-analysis examined randomized controlled trials of FES cycling for gait rehabilitation after stroke.
Ten studies involving 311 participants were included.
The meta-analysis found small, non-significant effects on measures including:
10-meter walking
50-meter walking
6-minute walking
The authors concluded that evidence for FES cycling improving gait after stroke remains limited and inconclusive.
This is a useful example of why individual positive findings should not be generalized to every FES application.
Evidence-Based Clinical Practice Analysis
The strongest clinical argument for FES is not simply:
"Electrical stimulation makes muscles stronger."
The more important argument is:
"FES can help a patient practice a functional movement that they cannot currently perform adequately."
This distinction is fundamental.
Example 1: Foot Drop
A patient cannot adequately dorsiflex during walking.
FES can provide dorsiflexion at the moment it is needed.
This creates:
functional assistance
repeated movement
sensory feedback
task-specific practice
Example 2: FES Cycling
A patient with spinal cord injury cannot voluntarily pedal.
FES can activate the relevant muscles to produce repeated cycling.
This provides:
muscle activation
movement repetition
metabolic activity
cardiovascular training potential
Example 3: Upper-Limb FES
A patient cannot adequately open the hand.
FES can stimulate finger/wrist extensors during a reaching or grasp-release task.
The stimulation becomes part of the movement rather than a separate passive treatment.
What FES Can and Cannot Do
FES can:
activate selected muscles
assist functional movement
provide repeated task practice
support gait training
assist foot clearance
provide muscle conditioning
contribute to cycling exercise
provide sensory feedback
FES cannot automatically:
restore a completely severed motor pathway
cure neurological disease
replace rehabilitation
guarantee normal walking
eliminate spasticity permanently
work equally well for every patient
Advantages of FES
Potential advantages include:
task-specific muscle activation
functional timing
repeated movement practice
potential strengthening
potential improvement in gait
potential improvement in activity
can assist patients with substantial weakness
can be integrated with active therapy
can be used for cycling and other repetitive exercise
provides both motor and sensory stimulation
Limitations
1. Requires appropriate nerve and muscle excitability
If the peripheral motor pathway cannot be electrically activated, conventional surface FES may be ineffective.
2. Requires correct timing
Poor timing can make the movement less effective or produce unwanted movement.
3. Can be uncomfortable
Higher stimulation intensities may produce discomfort.
4. Electrode placement is critical
Small changes in electrode position can alter the resulting movement.
5. Fatigue
Repeated electrical contractions can produce rapid muscle fatigue.
6. Equipment cost
Advanced sensor-controlled FES systems can be expensive.
7. Training and setup requirements
The clinician needs to understand both electrical stimulation and functional movement analysis.
8. Not appropriate for everyone
Medical history, neurological status, sensation, skin condition and implanted devices must be considered.
Common Clinical Mistakes
Mistake 1: Calling every muscle stimulation FES
If stimulation is not linked to a functional activity, it may be more accurately described as NMES/EMS rather than FES.
Mistake 2: Ignoring timing
FES depends heavily on synchronization with the task.
Mistake 3: Using the strongest possible stimulation
The goal is appropriate functional movement, not maximum intensity.
Mistake 4: Ignoring voluntary effort
Whenever possible, the patient should actively participate.
Mistake 5: Treating FES as a passive modality
The most meaningful applications are often active and task-specific.
Mistake 6: Assuming FES is superior to an AFO
Evidence in post-stroke foot drop suggests that FES and AFOs can produce similar improvements in walking speed, rather than one universally outperforming the other.
Myths and Misconceptions
Myth 1: FES is just EMS with a different name.
Not exactly.
FES incorporates functional timing and task performance.
Myth 2: FES permanently fixes foot drop.
FES can assist foot clearance and may improve functional outcomes, but it does not guarantee permanent restoration of normal motor control.
Myth 3: FES is only for people who cannot move.
Not necessarily.
People with partial voluntary movement may benefit because stimulation can augment their existing movement.
Myth 4: FES always improves walking speed.
Evidence is condition- and protocol-dependent.
Some systematic reviews demonstrate improvements, while other analyses show no significant benefit for particular walking outcomes.
Myth 5: FES replaces active rehabilitation.
It should generally be integrated into active rehabilitation rather than replacing it.
Frequently Asked Questions
What is the main purpose of FES?
The main purpose is to use electrical stimulation to assist or produce a functional movement.
What is the most common use of FES?
One of the best-known uses is stimulation of the peroneal/dorsiflexor system to assist foot clearance during walking in people with neurological foot drop.
Can FES help after stroke?
Yes. Research supports potential benefits for selected gait and activity outcomes, although effects are not consistent across every outcome measure.
Can FES help spinal cord injury?
It can be used for cycling, strengthening, standing, stepping and selected locomotor rehabilitation. Evidence supports potential benefits for several outcomes, but results vary substantially between protocols and patient populations.
Is FES painful?
It can feel uncomfortable, especially at the intensities required to produce strong muscle contractions, but treatment should remain within acceptable tolerance.
Can FES be used instead of an AFO?
For some people with foot drop, yes, FES can be an alternative management strategy. Evidence suggests that FES and AFOs can produce comparable improvements in walking speed after stroke.
How long should FES be used?
There is no universal duration. Treatment depends on the task, device, diagnosis and rehabilitation goal.
Does FES build muscle?
It can provide a muscle-training stimulus, particularly when large muscle groups are activated repeatedly, but the outcome depends on stimulation dose and the patient's overall rehabilitation programme.
Can FES reduce spasticity?
Some research, particularly involving FES cycling after spinal cord injury, suggests reductions in spasticity. However, the evidence remains heterogeneous.
Evidence-Based Takeaway
Functional Electrical Stimulation is different from conventional electrical muscle stimulation because the electrical contraction is deliberately integrated into a functional activity.
The basic process is:
Electrical stimulation → peripheral nerve activation → muscle contraction → correctly timed movement → functional practice
This makes FES particularly relevant to neurological rehabilitation.
Evidence supports potential benefits in areas such as:
post-stroke foot drop
gait rehabilitation
selected activity outcomes after stroke
FES cycling after spinal cord injury
muscle conditioning
selected spasticity-management programmes
However, the evidence is not uniformly positive for every outcome.
For example, post-stroke research has demonstrated improvements in some measures of gait and balance, while other walking measures show little or no significant difference.
Similarly, FES and ankle-foot orthoses can produce comparable walking-speed improvements after stroke, meaning the clinical decision should be individualized rather than based on the assumption that FES is always superior.
The most useful role of FES is therefore to help patients practice and perform movements that are otherwise difficult because of neurological weakness or impaired motor control.
Conclusion
Functional Electrical Stimulation is one of the most clinically interesting applications of electrotherapy because it connects electrical stimulation directly with purposeful movement.
Its fundamental principle is:
Stimulate the nerve → activate the muscle → synchronize the contraction → assist the functional task.
That final step makes FES different.
A patient with foot drop does not simply need their ankle muscles to contract while sitting. They need the muscles to activate at the correct moment during walking.
A patient with spinal cord injury does not simply need their quadriceps to contract. They may need repeated muscle activation during cycling or stepping.
A patient with impaired hand function does not simply need wrist and finger muscles to contract. They may need those muscles to activate during reaching, grasping or releasing an object.
This is why the clinical value of FES lies in functional integration.
Current research supports FES as a useful rehabilitation tool in selected neurological populations, particularly for foot drop and some gait-related applications. However, outcomes vary according to diagnosis, severity, stimulation parameters, timing, treatment dose and the rehabilitation programme in which FES is used.
The best clinical approach is therefore not:
"Use FES instead of exercise."
It is:
"Use FES to help the patient perform more meaningful movement, then progressively develop voluntary control, strength and functional independence."
That is the central role of FES in evidence-based physiotherapy.
Selected Research References
Hwang S, Song CS. Rehabilitative effects of electrical stimulation on gait performance in stroke patients: A systematic review with meta-analysis. NeuroRehabilitation. 2024. PMID: 38306066.
Alashram RA. Functional Electrical Stimulation Cycling for Gait Rehabilitation in Stroke Survivors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Physiotherapy Research International. 2026. PMID: 41778356.
da Cunha MJ, et al. Functional electrical stimulation of the peroneal nerve improves post-stroke gait speed when combined with physiotherapy: A systematic review and meta-analysis. Annals of Physical and Rehabilitation Medicine. 2021. PMID: 32376404.
Alvarenga L, et al. Ankle-foot orthoses and continuous functional electrical stimulation improve walking speed after stroke: a systematic review and meta-analyses of randomized controlled trials. Physiotherapy. 2020. PMID: 33120054.
Prenton S, Hollands KL, Kenney LP, Onmanee P. Functional electrical stimulation and ankle foot orthoses provide equivalent therapeutic effects on foot drop: A meta-analysis. 2018. PMID: 29227525.
Kanakis KA, et al. Electrical Stimulation and Motor Function Rehabilitation in Spinal Cord Injury: A Systematic Review. 2024. PMID: 38947571.
Fang CY, et al. The Effect and Dose-Response of Functional Electrical Stimulation Cycling Training on Spasticity in Individuals With Spinal Cord Injury: A Systematic Review With Meta-Analysis. 2021. PMID: 34867459.
Couper SK, Smith M. The Effects of Functional Electrical Stimulation Cycling on Muscle Spasticity in Individuals With Spinal Cord Injury: A Systematic Review. 2025. PMID: 40008155.
Unger J, Wiener JC, Patel P, Shakir U, Eng JJ. Effectiveness of Functional Electrical Stimulation Assisted Locomotor Training on Walking Outcomes Following Incomplete Spinal Cord Injury: Systematic Review and Meta-Analysis. 2026.
Howlett OA, Lannin NA, Ada L, McKinstry C. Functional electrical stimulation improves activity after stroke: a systematic review with meta-analysis. Archives of Physical Medicine and Rehabilitation. 2015. PMID: 25634620.
Clinical note: FES parameters, electrode placement, contraindications and safety precautions should always be individualized and checked against the specific device manufacturer's instructions, relevant clinical guidelines and the patient's neurological and medical status.
