Can Electrical Stimulation Improve Hand Opening After Stroke? What the Evidence Shows
NeuroRehab Team
Thursday, January 22nd, 2026
Nearly 800,000 people in the United States suffer strokes each year, and functional electrical stimulation gives them new hope. Stroke survivors often experience paralysis on one side of their body. This paralysis makes it hard to open their hand and affects their daily activities and independence by a lot. Research shows that electrical stimulation techniques could provide affordable solutions for these movement challenges.
Electrical stimulation helps stroke rehabilitation by using low levels of current to activate paralyzed muscles. This technique can improve hand strength and bring back normal function. Recent studies prove that patients who received newer electrical stimulation therapies did better in dexterity tests. They moved 4.6 blocks compared to just 1.8 blocks in conventional therapy groups. The treatment works best especially when you have patients less than two years after their stroke who can still move their fingers somewhat. Scientists keep finding more evidence that supports using electrical stimulation. Their research shows that combining brain stimulation with intensive rehabilitation helps survivors keep their improved function for up to one year.
Understanding Functional Electrical Stimulation (FES)
Electrical stimulation has transformed into a powerful therapeutic tool. Functional electrical stimulation (FES) stands out as one of its most promising applications that could revolutionize stroke rehabilitation.
What is functional electrical stimulation?
FES is a rehabilitation technology that uses small electrical currents to activate muscles weakened or paralyzed by brain or spinal cord damage [1]. The treatment works by sending electrical impulses through skin-placed electrodes. These impulses stimulate specific nerves and make muscles contract [2].
The United States saw the birth of FES in the 1960s when it was tested mostly on stroke patients. The technology remained experimental until clinical applications expanded in the 1980s and 1990s [2]. The science behind it is straightforward – electrical current causes peripheral neurons to depolarize, which leads to controlled muscle contractions [3].
FES stands apart from random electrical stimulation because of its targeted design. The stimulation creates functional, useful movements instead of random ones [2]. The technology helps the brain and muscles remember how to make proper movements as patients do specific tasks with FES support. This process could help rewire neural pathways [2].
How FES is different from general electrical stimulation
Therapeutic electrical stimulation and FES serve different purposes. Therapeutic stimulation creates lasting physiological changes that help recovery, while FES helps replace lost functions in real life [3]. FES targets motor nerves to contract muscles, but transcutaneous electrical nerve stimulation (TENS) works on sensory nerves to improve muscle tone and reduce pain without causing contractions [1].
FES systems come in two main types:
- Open-loop FES systems: These run on preset patterns that don’t respond to patient feedback [2]. Therapists use these systems following fixed protocols without making real-time changes.
- Closed-loop FES systems: These advanced systems use brain-computer interface (BCI) and electromyogram (EMG) control. They analyze and adjust stimulation based on the patient’s neural activity or muscle needs in real time [2].
Electrode placement adds another layer of variation. Invasive electrodes go near or inside target muscles using about 25mA current. Non-invasive electrodes stick to the skin and use 2mA to 120mA current [4]. Non-invasive methods make early treatment easier and allow changes without surgery.
Common applications in stroke rehabilitation
FES helps stroke patients in several ways. Hand muscles often benefit the most, especially with hand opening challenges [1]. Many stroke patients struggle with severe weakness in their distant muscles and don’t recover well on their own. That’s why FES has become such a valuable treatment option [3].
FES helps stroke patients by:
- Bringing back motor skills and muscle strength [2][4]
- Making movements easier and muscles stronger [4]
- Reducing muscle stiffness and making movements smoother [2]
- Making walking and balance better [2]
- Helping the brain create new connections through repeated use [4]
Studies show real benefits from FES treatment. Patients show better scores on Fugl-Meyer Assessment, modified Ashworth Scale for spasticity, and balance tests after six weeks of FES compared to regular electrical stimulation [2]. New technology lets patients use FES at home, giving them control over their hand rehabilitation and chances to practice more often [1].
FES works in two ways. It improves muscle strength and flexibility directly. More importantly, it stimulates sensory and motor nerve fibers, which could reorganize brain networks and create lasting changes in brain plasticity [4].
How Electrical Stimulation Affects Hand Function
The way electrical stimulation affects our nervous system goes way beyond simple muscle contraction. It provides exceptional benefits through multiple biological mechanisms that help stroke patients recover. These mechanisms explain why electrical stimulation is such a promising way to improve hand function after stroke.
Muscle activation and motor relearning
Stroke rehabilitation faces a basic challenge – patients cannot voluntarily activate paralyzed muscles. Research shows that electrical stimulation can produce equal force on both sides [5] even when the affected side is nowhere near as strong as the unaffected side. This explains how the nerve-to-muscle pathway stays intact despite brain damage.
Electrical stimulation helps stroke survivors move their hands through electrodes placed on their skin. This external help bridges the gap between what patients want to do and what they can actually do during recovery.
Motor relearning happens as the brain builds new connections through repeated practice with electrical assistance. The process has several key parts:
- Repetition of appropriate movement patterns
- Task-specific training with functional goals
- Active participation from the patient
Patient involvement is vital to make stimulation work. Simple passive stimulation helps somewhat, but the biggest improvements happen when patients try to move while getting stimulation [2]. This combined effort builds a stronger brain-muscle connection and creates better nerve changes. Research shows that patients who received both electrical stimulation and physical therapy improved more than those who just exercised [2].
Cortical reorganization and neuroplasticity
The brain can adapt remarkably well after a stroke through neuroplasticity – its ability to form new nerve connections after injury or experience. Electrical stimulation boosts this natural process in several ways.
Electrical stimulation sends more signals to the brain, which helps reorganize brain circuits. Studies using fMRI and TMS confirm that stimulating nerves can increase motor-evoked potential and active voxel count in the brain’s motor areas [6]. These changes show increased activity in brain cells that control hand function.
Brain activity patterns change as recovery progresses. Right after a stroke, the main motor area becomes less active while other brain regions work harder to compensate [7]. The right kind of electrical stimulation can boost these backup systems.
The connection between brain signals and muscle activity – called corticomuscular coherence (CMC) – gets much stronger after four weeks of electrical stimulation [6]. This improved brain-muscle communication relates to better control in force-related tasks.
Role of afferent feedback in recovery
Sensory feedback is one of the most important yet overlooked parts of electrical stimulation. When muscles contract from stimulation, they create rich sensory feedback through multiple channels:
- Direct sensation from the stimulation
- Position sense from joints, tendons, and muscles
- Movement and position information from touch sensors
This complete sensory input boosts activity in working nerve pathways to the brain and helps create new connections [2]. Research findings show that “motor recovery may be enhanced with the provision of an appropriate dose of afferent stimulation normally arising from functional activities” [5].
Motor neurons become easier to activate when they receive more sensory input. This helps weak signals from the brain create voluntary movements [2]. Regular sessions strengthen these nerve pathways and lead to lasting improvements.
Sensory feedback is especially valuable because it gives the brain information it might miss due to paralysis. Studies show that combining electrical stimulation with real movement creates two types of sensory input. This combination helps the brain adapt even better [8].
The best results come from using electrical stimulation with practical, goal-focused activities instead of simple movements. This approach activates multiple brain circuits at once and helps relearn complex hand movements needed for daily tasks after stroke.
Types of FES Systems Used in Stroke Recovery
The FES rehabilitation technology map continues to change. Systems of all sizes now give patients different ways to participate and maintain control. Studies show these systems have grown more sophisticated, each using unique ways to deliver electrical stimulation that improves hand function after stroke.
Open-loop FES systems
Open-loop FES systems offer the most direct path to electrical stimulation therapy. Therapists control these devices by hand and apply electrical stimulation to specific muscles. They use preset settings like stimulation intensity, duration, and ON/OFF cycles [2]. These systems are available in clinical settings because of their simple design. However, they cannot adjust stimulation based on how patients respond.
Studies prove open-loop FES helps hand rehabilitation. A trial with 30 patients showed that two-channel FES with four surface electrodes reduced wrist flexor spasticity substantially [2]. The results of another study revealed better functional hand opening (3.2–8.8 cm) after FES targeted both reaching and hand opening muscles [2].
On top of that, research by Meadmore’s team showed a 4.4-point improvement on clinical assessment scales after patients went through 18 sessions of FES. The treatment focused on shoulder, elbow, and wrist muscles [2]. This evidence tells us that even simple open-loop systems can help reduce upper limb problems.
EMG-controlled FES systems
EMG-controlled FES systems improve upon open-loop systems by using the patient’s own muscle activity as feedback. These systems detect muscle electrical activity through electromyography. This information helps trigger and adjust stimulation intensity right away [2].
EMG-controlled systems work in two main ways:
- EMG-triggered FES: Starts stimulation once muscle activity hits a set threshold
- EMG-controlled FES: Starts stimulation and keeps adjusting intensity based on the patient’s muscle effort
This method lines up with motor learning principles because patients must participate actively. Research backs this up. Shindo’s team ran a trial using myoelectrically controlled electrical stimulation to help finger extension [2]. They placed electrodes on paretic extensor digitorum communis muscles to detect activity and control stimulation intensity.
MeCFES (Myoelectrically Controlled Functional Electrical Stimulation) marked a big step forward. A trial with 11 stroke survivors tested this system [2]. It tracked muscle activity from wrist and finger extensors to control extension movements. A newer wearable version called “FITFES” helps with task-oriented therapy in ambulatory settings [2].
BCI-controlled FES systems
Brain-Computer Interface (BCI) controlled FES systems stand at technology’s cutting edge. These systems pick up the patient’s intent to move directly from brain activity and turn it into FES commands. This creates a direct path from thought to muscle activation [2].
A typical BCI-FES system has three main parts:
- A BCI unit that captures and processes brain signals (usually via EEG)
- A BCI-FES interface assembly that translates these signals
- An FES module that sends the right stimulation to muscles [4]
Therapy sessions involve patients thinking about movements or watching actions. These activities create detectable changes in brain activity. Special decoding algorithms match these signals to specific imagined movements, which lets patients control the FES device [4].
Clinical evidence shows BCI-FES systems work better than standard approaches. Cincotti’s team ran a trial that proved patients using BCI-FES therapy recovered better than those using regular FES [2]. Li’s research showed a 77% motor imagery task classification accuracy and better rehabilitation results in the BCI-FES group [2].
The most promising finding shows that BCI-coupled FES helps chronic stroke survivors recover better than sham FES. Patients managed to keep these improvements for 6-12 months after therapy ended [3].
Patient Factors That Influence FES Outcomes
Stroke survivors respond differently to functional electrical stimulation, and patient-specific factors substantially influence their rehabilitation outcomes. Clinicians can determine which patients might benefit most from FES intervention by learning about these variables and optimizing treatment protocols.
Stage after stroke: acute vs chronic
The success of FES treatment depends heavily on when doctors start the intervention after stroke. Research shows that FES works best when applied during the recovery phase (1-6 months post-stroke). Patients show better improvement in ankle dorsiflexion range of motion during this period compared to both acute (≤1 month) and chronic (≥6 months) phases [9]. The benefits don’t stop at this window though.
A randomized controlled trial with forty-six subjects averaging 70.9 years showed remarkable results. Researchers started FES treatment about 8.7 days after stroke [10]. Every subject in the FES group learned to walk again, with 84.6% going back home. The placebo group saw only 53.3% return home, while the control group had 46.2% [11].
Patients who received FES started walking 2-3 days earlier than those who got placebo stimulation or standard rehabilitation [10]. While early intervention clearly helps, chronic stroke patients might still benefit from FES. Motor function can improve through boosted rehabilitative therapy even in chronic stages, though the brain might reorganize differently [12].
Severity of hand impairment
A patient’s baseline motor function plays a big role in their response to FES therapy. Research reveals different treatment effects based on severity:
- Mild impairment: Patients respond well with medium to large effect sizes (standardized effect size ≥0.5) [1]
- Moderate impairment: These patients typically see the best results from FES interventions [1]
- Severe impairment: While showing improvements in impairment measures, patients with severe deficits don’t translate these gains into functional abilities easily [1]
A case study showed promise even in severe cases. A 22-year-old who couldn’t extend their fingers or thumb 18 years after childhood-onset stroke improved their hand function and quality of life through task-specific FES training [13]. About 50-60% of stroke survivors still have some motor deficits after complete rehabilitation – an important fact to consider before treatment [14].
Presence of spasticity and muscle atrophy
Spasticity affects roughly one-third of stroke patients [12] and creates both challenges and opportunities for FES intervention. Involuntary muscle contractions limit joint movement and stymie functional recovery [15]. Lower extremity spasticity, especially in the foot, makes walking difficult due to poor balance, asymmetric posture, and reduced motor control [15].
Spasticity can both help and hurt FES treatment. Too much spasticity might make electrical stimulation harder, which explains why some studies exclude such cases [12]. However, proper FES application can reduce spasticity. One study revealed the active NMES group improved by 35% in plantarflexor muscle spasticity, while the sham group declined by 10.74% [16].
Muscle atrophy after stroke also affects FES outcomes. More than 80% of survivors have trouble walking [5] due to hemiplegia-related muscle loss [17]. Multiple factors cause this atrophy: denervation, disuse, inflammation, and muscle tissue changes [5]. Long-term immobilization changes tissues – losing sarcomeres and turning muscle into connective tissue – which can make FES less effective [12].
FES might help prevent muscle loss, but a four-week study found no real change in stimulated muscle thickness for quadriceps and hamstrings in the affected limb [17]. Short-term FES protocols might not be enough to address muscle atrophy, suggesting longer treatment periods might work better.
Clinical Evidence: What the Research Shows
Research studies on functional electrical stimulation show strong evidence of its benefits in stroke rehabilitation. The clinical outcomes reveal promising results but also highlight key points about putting it into practice.
Improvements in FMA and ARAT scores
FES treatments show clear improvements in standard assessment tools. A detailed review of 25 studies found that FMA scores improved by a lot with different FES methods: manually controlled FES (mean difference = 5.6), BCI-controlled FES (mean difference = 5.37), and EMG-controlled FES had the best results (mean difference = 14.14) [2]. The ARAT scores also jumped higher with EMG-controlled FES (mean difference = 11.9) [2].
CCFES has proven particularly effective. One study showed UEFM scores improved by 8.1 points in the CCFES group, while conventional neuromuscular electrical stimulation groups only gained 3.7 points [18]. So 67% of CCFES patients achieved meaningful clinical improvement on the UEFM compared to just 42% in standard stimulation groups [18].
Comparisons with conventional therapy
Direct comparisons usually favor FES over standard rehabilitation methods. Studies comparing CCFES to task-oriented therapy (TOT) show FES leads by 3.7 points on Fugl-Meyer scores and 4.1 points on ARAT scores [18]. But not every study shows clear advantages. Some reviews suggest that while FES works better than no treatment, its edge over conventional therapy remains unclear [19].
Therapists’ adoption rates reflect these mixed results. About 45% say they regularly use electrical stimulation in their practice [6]. The adoption rate jumps to 85% among therapists with extra training, compared to 44% without it [6]. Therapists also have different views about how well it works during various recovery stages [6].
Limitations in current studies
The current research has several weak spots. Most studies use small groups of 1-51 participants, which falls short of the 64 needed for statistical significance [8]. Few studies track patients long enough to see if the improvements last [8].
The research faces other challenges too. These include strict patient selection criteria [20], different protocols for stimulation frequency and duration [12], and lack of standard approaches for different types of patients [12]. A survey points out that while FES looks promising, we need more research to understand what resources it takes – time, equipment, and training – to make it work well [6].
Optimizing FES for Better Hand Recovery
The therapeutic benefits of functional electrical stimulation depend on several core factors. Each patient needs an optimal approach that balances technical settings, treatment schedules, and the rehabilitation environment.
Choosing the right stimulation parameters
The right FES parameter configuration tailored to individual needs drives successful outcomes. Research shows these beneficial FES parameters stay relatively stable between sessions. Their high to very high repeatability makes clinical implementation consistent [21]. Therapists and patients must work together to adjust these parameters based on the patient’s feedback about improvement [21]. The treatment of functional tasks like hand opening during drinking follows a step-by-step approach. Therapists first identify functions to train (reaching/grasping), then select the task order. They usually start with gross motor tasks and progress to fine movement control [7].
Importance of therapy duration and frequency
The evidence points to specific dosage recommendations that maximize FES benefits. Most trials showed results with FES sessions of 45-60 minutes, 3-5 days weekly, for 8-16 weeks – about 40 sessions total [7]. Patients spend 30-45 minutes of each therapy hour doing daily activities with FES support [7]. The patient’s tolerance plays a vital role. Most people can handle one 60-minute session daily and complete 10-15 repetitions of a specific movement pattern before they tire [7]. These parameters change based on each person’s injury extent, chronicity, and neuromuscular system status.
Home-based FES and patient engagement
Home rehabilitation with FES technology shows great promise beyond clinical settings. A study revealed high adherence rates (74.03%) and patient satisfaction at 73% [22]. Patients averaged 414 minutes of unsupervised exercise weekly [22]. Patient participation makes a significant difference. The most effective protocols ask patients to imagine the movement first, then try it voluntarily before adding electrical stimulation [7]. The therapy reduces FES assistance gradually to deepen muscle group commitment, eventually moving to full voluntary control [7]. This approach helps patients regain control of their hand [23] and improves outcomes through increased engagement while reducing healthcare costs [23].
Conclusion
FES technology has brought major advances to stroke rehabilitation. It helps patients who don’t deal very well with hand opening problems. Studies show clear improvements in standard tests like the Fugl-Meyer Assessment and Action Research Arm Test when patients use FES therapies. Stroke survivors now have more options beyond regular therapies.
The right timing makes a big difference with FES treatment. Patients get better results when they start early in recovery (1-6 months after stroke). The treatment still helps people in later stages too. A patient’s level of hand impairment affects their progress. Those with moderate impairment usually respond best to the treatment. FES helps with muscle stiffness and improves movement patterns at the same time.
State-of-the-art developments have expanded FES options. Simple open-loop systems offer basic benefits. EMG-controlled systems that respond to a patient’s muscle activity work even better. Brain-Computer Interface controlled FES is the latest innovation. It creates a direct path from thought to muscle activation and leads to lasting rehabilitation effects.
The best FES therapy needs the right stimulation settings, treatment length, and patient participation. Most successful treatments include 45-60 minute sessions several times a week for 8-16 weeks. Home-based programs help patients continue their progress outside clinics. These programs let patients take charge of their recovery experience.
Current research looks promising, but small sample sizes and lack of standard protocols create challenges. In spite of that, FES technology keeps improving. It gives stroke survivors more chances to regain hand function and live better lives. FES has become a valuable part of complete stroke rehabilitation programs. It could change recovery outcomes for many patients worldwide.
Key Takeaways
Research reveals that functional electrical stimulation (FES) offers significant hope for stroke survivors struggling with hand function, with evidence showing measurable improvements in motor recovery and daily activities.
• FES significantly improves hand function: Studies show EMG-controlled systems achieve 14.14-point improvements in Fugl-Meyer scores, outperforming conventional therapy approaches.
• Timing matters for optimal results: Early intervention within 1-6 months post-stroke yields better outcomes, though chronic patients can still benefit from treatment.
• Advanced systems deliver superior outcomes: Brain-computer interface FES creates lasting motor recovery that persists 6-12 months after treatment completion.
• Patient engagement enhances effectiveness: Active participation during stimulation—combining voluntary effort with electrical assistance—produces better neuroplastic changes than passive treatment.
• Home-based programs extend benefits: Patients show 74% adherence rates with home FES systems, averaging over 400 minutes of weekly exercise while maintaining control over their rehabilitation.
The evidence strongly supports FES as a valuable addition to stroke rehabilitation programs, offering patients new pathways to regain hand function and independence through targeted electrical stimulation therapy.
References
[1] – https://www.researchgate.net/figure/mpact-of-Severity-of-Impairment-on-Changes-in-Outcome-Measures_tbl2_7371302
[2] – https://pmc.ncbi.nlm.nih.gov/articles/PMC10739305/
[3] – https://www.nature.com/articles/s41467-018-04673-z
[4] – https://www.frontiersin.org/journals/human-neuroscience/articles/10.3389/fnhum.2024.1438095/full
[5] – https://pmc.ncbi.nlm.nih.gov/articles/PMC8984173/
[6] – https://pmc.ncbi.nlm.nih.gov/articles/PMC12488299/
[7] – https://pmc.ncbi.nlm.nih.gov/articles/PMC7364342/
[8] – https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2023.1272992/full
[9] – https://www.sciencedirect.com/science/article/pii/S1052305725000588
[10] – https://www.ahajournals.org/doi/10.1161/01.str.0000149623.24906.63
[11] – https://pubmed.ncbi.nlm.nih.gov/15569875/
[12] – https://pmc.ncbi.nlm.nih.gov/articles/PMC4178310/
[13] – https://www.archives-pmr.org/article/S0003-9993(09)00516-4/fulltext
[14] – https://www.sciencedirect.com/science/article/pii/S1052305721001968
[15] – https://pmc.ncbi.nlm.nih.gov/articles/PMC5332979/
[16] – https://pmc.ncbi.nlm.nih.gov/articles/PMC10742606/
[17] – https://www.researchgate.net/publication/398148444_Effect_of_functional_electrical_stimulation_on_changes_in_muscle_mass_following_stroke_and_functional_abilities_in_hemiplegic_subjects
[18] – https://www.ahajournals.org/doi/10.1161/STROKEAHA.125.052891
[19] – https://strokengine.ca/en/interventions/functional-electrical-stimulation-upper-extremity/
[20] – https://pmc.ncbi.nlm.nih.gov/articles/PMC11988965/
[21] – https://pubmed.ncbi.nlm.nih.gov/34253404/
[22] – https://onlinelibrary.wiley.com/doi/10.1111/aor.14922
[23] – https://fescenter.org/new-electrical-stimulation-therapy-may-improve-hand-function-after-stroke/
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