What You Will Learn
In this chapter, we look at how FES cycling applies to specific neurological conditions. The benefits we described in Chapter 4 do not apply equally to everyone: the nature of your condition, the level and completeness of your injury, and whether your lower motor neurons are intact all influence what FES cycling can realistically achieve for you. We will cover spinal cord injury (both complete and incomplete), stroke, multiple sclerosis, cerebral palsy, Parkinson's disease, transverse myelitis, and cauda equina syndrome. For each, we explain what the evidence shows, what to expect, and where the limitations lie.
A Critical Distinction: Upper and Lower Motor Neurons
Before we look at individual conditions, there is one concept that is essential to understand. It determines whether FES cycling will work for you at all.
Your nervous system uses two sets of motor neurons to control movement. The upper motor neurons run from the brain down through the spinal cord. The lower motor neurons run from the spinal cord out to the muscles themselves. When you decide to move your leg, the upper motor neurons carry the signal down the spinal cord, and the lower motor neurons carry that signal the final distance to the muscle, making it contract.
FES cycling works by stimulating the lower motor neurons. The electrical pulses delivered through the skin excite these nerves, which in turn make the muscles contract. For this to work, the lower motor neurons must be intact. If the damage is to the upper motor neurons (as in most spinal cord injuries above the T12 level, most strokes, and most cases of multiple sclerosis), the lower motor neurons are unharmed, and FES cycling can produce strong, useful muscle contractions.
If the lower motor neurons themselves are damaged (as can happen in cauda equina syndrome, some lower spinal injuries, and certain peripheral nerve conditions), the muscles become "denervated." A denervated muscle will not respond to the type of electrical stimulation used in FES cycling. It requires a completely different approach, which we touch on later in this chapter and cover in our companion book on electrical stimulation for denervated muscle.
This distinction matters because some people have injuries that involve both upper and lower motor neuron damage. Understanding which type of damage applies to your muscles is essential for choosing the right form of electrical stimulation.
Spinal Cord Injury
Spinal cord injury is the condition for which FES cycling has the longest and strongest evidence base. Research dating back to the 1980s has extensively studied the effects of FES cycling in this population, and this is where the majority of our own clinical experience lies.
Complete Spinal Cord Injury (ASIA A)
A complete spinal cord injury means there is no motor or sensory function preserved below the level of the injury, as measured by the ASIA (American Spinal Injury Association) classification system. However, as we mentioned in the foreword and discussed above, "complete" does not necessarily mean the spinal cord has been severed. It means that clinically, no signals are getting through. The important point for FES cycling is that the lower motor neurons below the injury are usually intact.
For someone with a complete injury above T12, FES cycling is typically very effective. Because there is no voluntary control of the leg muscles, the stimulator does all the work: it triggers the muscle contractions that drive the pedals. In the early sessions, the muscles will fatigue quickly, and with regular training, this improves.
The benefits we described in Chapter 4 apply most directly to this group. The evidence for improvements in muscle mass, cardiovascular fitness, bone density, spasticity reduction, and circulation is strongest in the complete spinal cord injury population. Many of our clients with complete injuries have used FES cycling for years as a core part of their long-term health management.
If you have a complete injury and no sensation in the areas where the electrodes are placed, you will not feel the stimulation. You will see your muscles contracting and your legs moving, but there will be no accompanying sensation. Most people become accustomed to this quickly.
If your injury is at or below T6, autonomic dysreflexia is generally not a concern during FES cycling. If your injury is above T6, your clinical team may monitor you carefully during initial sessions, as FES cycling can occasionally trigger an autonomic dysreflexia episode. We cover this in detail in Chapter 9.
Incomplete Spinal Cord Injury (ASIA B, C, D)
An incomplete spinal cord injury means that some motor or sensory function is preserved below the level of injury. This covers a wide spectrum: from someone who has some sensation but no voluntary movement (ASIA B) through to someone who can move their legs against gravity but with reduced strength (ASIA D).
For people with incomplete injuries, FES cycling can be particularly valuable in a different way. Because some neural pathways remain intact, there is greater potential for neuroplastic change, and the combination of voluntary effort with electrical stimulation can be especially beneficial.
Many of our clients with incomplete injuries can contribute some voluntary pedalling effort, at least for a portion of the session. The FES system supports them: when their own effort falters, the stimulation intensity can increase to maintain active cycling. This means they can exercise for longer and at greater intensity than they could manage on their own. As we noted at the end of Chapter 4, this is one area where FES adds real value even for people who feel they might manage on a passive bike alone.
For those with preserved sensation (common in incomplete injuries), the stimulation will produce a tingling or pulsing feeling beneath the electrodes. This is always adjustable, and the vast majority of people tolerate it well. Occasionally, someone with heightened sensitivity may need a more gradual introduction to the level of stimulation.
The evidence for functional improvements (such as improved walking ability) is stronger in the incomplete spinal cord injury population than in the complete injury population. Meta-analyses have shown improvements of around 12 metres in six-minute walk tests and significant reductions in timed-up-and-go scores following FES cycling programmes. These gains are thought to stem from a combination of increased muscle strength, reduced spasticity, and neuroplastic adaptation.
However, it is important to manage expectations. Not everyone with an incomplete injury will see functional recovery. The degree of improvement depends on many factors, including the nature and extent of the remaining neural connections, the time since injury, and the individual's overall health. What we can say is that FES cycling gives the nervous system the best possible opportunity to make use of whatever connections remain.
The ASIA Score: Useful but Not Absolute
We should add a word about the ASIA classification. It is an invaluable clinical tool, but it is not a tablet of stone. We have met many people over the years who were told, based on their ASIA score, that certain functions would never return, only to discover through rehabilitation that their situation was more nuanced than the initial classification suggested. Spinal cord injuries are highly variable, and even people with the same ASIA score can have quite different capabilities. The classification should inform your expectations but never define your limits.
Stroke
Stroke is the second most common condition we see in the context of FES cycling, though in the UK, it is far less common for stroke survivors to access FES cycling than it is for people with spinal cord injuries. This is largely a matter of funding rather than clinical suitability.
A stroke occurs when the blood supply to part of the brain is interrupted, causing damage to brain tissue. The resulting effects depend on which part of the brain is affected. For many stroke survivors, the consequence is weakness or paralysis on one side of the body (hemiplegia or hemiparesis). Because the damage is in the brain (an upper motor neuron problem), the lower motor neurons and the muscles themselves are intact. FES cycling can therefore produce useful muscle contractions in the affected leg.
What the Evidence Shows
Research into FES cycling for stroke is growing, though the volume of evidence is smaller than for spinal cord injury. Studies have demonstrated improvements in:
- Walking ability: Stroke survivors using FES cycling have shown measurable improvements in gait speed, with one study reporting gains of 0.5 metres per second compared with 0.1 metres per second from passive cycling alone.
- Muscle strength: Lower-extremity motor scores improve, and the affected leg can regain strength, translating into better functional mobility.
- Spasticity: Many stroke survivors experience spasticity in the affected limbs. FES cycling can help reduce this, following the same mechanisms we described in Chapter 4.
- Neuroplasticity: This is perhaps the most significant consideration for stroke. The brain retains the capacity to reorganise itself after injury, and the repeated, rhythmic sensory and motor input provided by FES cycling aligns with the principles known to promote beneficial neuroplastic change: repetition, intensity, task specificity, and salience.
Practical Considerations for Stroke
Unlike someone with a complete spinal cord injury, most stroke survivors retain some voluntary control of their affected leg. FES cycling can supplement this effort, allowing the person to exercise at a meaningful intensity for longer than they could manage on their own. This is the same principle we described for incomplete spinal cord injuries.
One important consideration is timing. The evidence in stroke rehabilitation broadly supports early and intensive intervention. The first three to six months after a stroke (the subacute phase) are generally considered the period of greatest potential for recovery. Starting FES cycling during this window may offer the best opportunity for neuroplastic benefit. However, gains are certainly possible in the chronic phase (beyond six months) as well. No one ever complained that they received too much therapy.
The challenge for stroke survivors in the UK is access. FES cycling systems have historically been expensive, and unlike spinal cord injury (where medico-legal or insurance funding is often available to individuals as a consequence of an accident), most stroke survivors do not have access to this kind of financial support. Newer, more affordable products are beginning to change this picture, and we discuss equipment options in Chapter 8.
Multiple Sclerosis
Multiple sclerosis (MS) is a condition in which the immune system attacks the myelin sheath (the protective covering around nerve fibres) in the brain and spinal cord. This disrupts the transmission of nerve signals, leading to a wide range of symptoms including muscle weakness, fatigue, spasticity, and difficulty with balance and coordination.
Because MS affects the central nervous system (upper motor neurons), the lower motor neurons and muscles are typically intact, meaning FES cycling can produce useful muscle contractions. However, MS is a variable and often unpredictable condition, and the response to FES cycling can differ considerably between individuals.
What the Evidence Shows
The evidence base for FES cycling in MS is smaller than for spinal cord injury, but it is positive. A study by Backus and colleagues (2017) examined FES cycle training outcomes in non-ambulatory individuals with MS and found improvements in muscle function and overall fitness. FES cycling has been shown to be "particularly effective" for MS in comparative reviews of electrical stimulation approaches.
For people with MS, the benefits of FES cycling are broadly similar to those described in Chapter 4: improved muscle strength, better cardiovascular fitness, reduced spasticity, and enhanced circulation. Many people with MS also experience profound fatigue, and while this might seem like a barrier to exercise, regular FES cycling can actually help manage fatigue over time by improving overall conditioning and cardiovascular efficiency.
Practical Considerations for MS
MS presents some unique challenges for FES cycling. The condition can fluctuate, with relapses and remissions that affect a person's functional abilities from week to week. FES cycling programmes need to be adaptable, with the flexibility to adjust intensity and session duration based on how the person is feeling on any given day.
For people with MS who retain some ability to pedal voluntarily, FES cycling supports them in the same way it supports those with incomplete spinal cord injuries: it supplements their own effort, allowing them to exercise at a meaningful level for longer. For those with more severe weakness, stimulation can enable the muscles to do most of the work.
Most people with MS will have some preserved sensation, so they will feel the stimulation. As with other conditions, the intensity is adjustable, and most people tolerate it well.
The cost barrier applies particularly to people with MS, who are less likely than spinal cord injury clients to have access to medico-legal or other dedicated funding. We hope that as products become more affordable, FES cycling will become accessible to more people with MS who could benefit from it.
Cerebral Palsy
Cerebral palsy (CP) is a group of conditions that affect movement and posture, caused by damage to the developing brain (most commonly before or during birth). The nature of the motor impairment varies widely: some people have mild weakness in one limb, while others have significant spasticity and weakness affecting all four limbs.
Because cerebral palsy is an upper motor neuron condition, the lower motor neurons and muscles are intact, and FES cycling can produce useful contractions. The research in cerebral palsy is more recent and smaller in volume than for spinal cord injury, but the results are encouraging.
What the Evidence Shows
A randomised controlled trial by Armstrong and colleagues (2019) examined the effects of FES-powered cycling in children with cerebral palsy. The study found that FES cycling increased muscle cross-sectional area and reduced intramuscular fat, similar to the findings in spinal cord injury populations. Adolescents with CP have been shown to increase their cycling cadence by 25% and power output by 200% after seven weeks of FES cycling, with improved pedalling symmetry and endurance.
Spasticity reduction is another important benefit. The rhythmic muscle contractions of FES cycling help manage the spasticity that is a central feature of many forms of cerebral palsy. For children and young people with CP, FES cycling can also provide a form of structured physical activity that might otherwise be difficult to access.
Practical Considerations for Cerebral Palsy
Working with children and young people requires particular attention to the setup of the cycling system. Smaller limbs, different ranges of motion, and the need for age-appropriate engagement all need to be considered. The stimulation intensity must be carefully calibrated, and sessions should be structured to maintain the child's interest and cooperation.
For children with preserved sensation (common in CP), the sensation of electrical stimulation is usually well tolerated, but a gradual introduction is advisable. Parents and carers typically become confident with the setup and electrode placement after initial training.
Parkinson's Disease
Parkinson's disease is a progressive neurological condition caused by the loss of dopamine-producing neurons in a part of the brain called the substantia nigra. It affects movement control, causing symptoms such as tremor, rigidity, slowness of movement (bradykinesia), and problems with balance and gait.
Parkinson's is fundamentally different from spinal cord injury or stroke in that the muscles and their nerve supply are intact: the problem lies in the brain's ability to initiate and control movement smoothly. Because the lower motor neurons are intact, FES cycling can elicit muscle contractions, but its role in Parkinson's is somewhat different from that in the conditions we have discussed so far.
What the Evidence Shows
There is limited research specifically on FES cycling for Parkinson's disease. However, the evidence for the benefits of cycling exercise in general for Parkinson's is substantial. Research has consistently shown that cycling can improve motor function, reduce rigidity, and enhance gait performance in people with Parkinson's. The "forced exercise" concept, in which people cycle at a pace faster than they would choose voluntarily, has been associated with improvements in motor symptoms comparable to those achieved with medication.
FES cycling could serve a useful role for people with Parkinson's who have difficulty generating sufficient voluntary effort to cycle at the intensity needed for therapeutic benefit. The electrical stimulation can supplement their effort, enabling a more vigorous workout than they might achieve on their own. This is a practical benefit, even though the underlying rationale is different from that in spinal cord injury.
Practical Considerations for Parkinson's
People with Parkinson's typically have full sensation, so they will feel the stimulation. In our experience, most tolerate it well, though the combination of stimulation with the rigidity that characterises Parkinson's may require careful adjustment of parameters.
Parkinson's disease fluctuates through the day, often in relation to medication timing. Exercise sessions may be most productive when timed to coincide with "on" periods (when medication is working well). Fatigue and apathy, both common features of Parkinson's, can make adherence to an exercise programme challenging, and the structured nature of FES cycling (with its defined sessions and measurable outputs) can help provide motivation and routine.
The specific evidence for FES cycling in Parkinson's is thin. The broader evidence for cycling exercise in Parkinson's is strong, and FES cycling offers a way to access those benefits more fully. But dedicated research examining FES cycling outcomes specifically in Parkinson's populations is still needed.
Transverse Myelitis
Transverse myelitis is a rare neurological condition caused by inflammation across a section of the spinal cord. It can produce symptoms very similar to a spinal cord injury: weakness or paralysis, numbness, and bladder and bowel dysfunction. Some people recover fully; others are left with permanent disability.
Because transverse myelitis affects the spinal cord, the principles are similar to those for spinal cord injury. If the lower motor neurons are intact (as they are in most cases where the inflammation is above the T12 level), FES cycling can produce useful muscle contractions and deliver the same benefits described in Chapter 4.
However, there is an important complication. Depending on where the inflammation occurs, some degree of lower motor neuron damage (denervation) is possible. If this is the case, the affected muscles will not respond to standard FES cycling. A clinical assessment that includes testing your muscles' response to electrical stimulation will clarify whether standard FES is appropriate or a specialised denervation stimulation approach is needed.
People with transverse myelitis may also have associated conditions, such as neuromyelitis optica spectrum disorder (NMOSD) or multiple sclerosis, which can affect the course of the illness and the response to rehabilitation. Your clinical team will take these into account when planning your programme.
Cauda Equina Syndrome
Cauda equina syndrome (CES) deserves special mention because it presents a fundamentally different situation from the other conditions in this chapter.
The cauda equina is the bundle of nerve roots that extends below the end of the spinal cord, from approximately the L1-L2 vertebral level downward. These are lower motor neurons. When they are damaged (by disc herniation, trauma, tumour, or other causes), the muscles they supply become denervated. This means the muscles lose their nerve supply entirely.
Standard FES cycling will not work for denervated muscles. The electrical pulses used in FES cycling are designed to stimulate nerves, which then activate muscles. If the nerves are damaged, there is nothing for the standard stimulation to act upon.
This does not mean that nothing can be done. Specialised electrical stimulation using fundamentally different parameters (much longer pulse widths and higher currents) can directly activate the muscle fibres themselves, bypassing the damaged nerves. This approach was developed through the European RISE research programme and has demonstrated that even long-term denervated muscle can be preserved and improved. However, it requires different equipment and a different protocol from FES cycling.
If you have cauda equina syndrome, the first step is a thorough assessment to determine the extent of denervation. Some people with CES have a mix of denervated and innervated muscles, and the approach needs to be tailored accordingly. We cover the denervation topic in detail in our companion book, Electrical Stimulation for Denervated Muscle.
Other Conditions
FES cycling may also be relevant for people with other neurological conditions that result in lower limb weakness or paralysis, provided the lower motor neurons are intact. These include:
- Traumatic brain injury: Where the consequences include lower limb weakness, FES cycling can be used on the same principles as for stroke.
- Guillain-Barré syndrome: In the recovery phase, once reinnervation is underway and some nerve function has returned, FES cycling may help rebuild strength. Timing needs careful clinical judgement.
- Post-surgical nerve recovery: After nerve repair surgery, electrical stimulation can help maintain muscle viability while waiting for nerves to regenerate. FES cycling may become appropriate once sufficient reinnervation has occurred.
In all cases, a clinical assessment is essential to determine whether FES cycling is appropriate and to identify any denervation that would require a different approach.
The Importance of Individual Assessment
If there is one message to take from this chapter, it is that no two people are the same, even when they share the same basic diagnosis. The level and completeness of a spinal cord injury, the location and severity of a stroke, the pattern of weakness in MS or cerebral palsy: all of these influence what FES cycling can achieve for a particular individual.
A thorough clinical assessment before you begin is essential. This should include testing your muscles' response to electrical stimulation, evaluating your range of motion, identifying any contraindications, and establishing a baseline against which to measure progress. Your programme should then be tailored to your specific situation and adjusted over time as your muscles and fitness change.
We have worked with FES cycling for many years, and one of the things we have learned is that the people who do best are those who come with realistic expectations, a willingness to commit to regular exercise, and an understanding that progress is measured in weeks and months rather than days.
Chapter Summary
- FES cycling requires intact lower motor neurons. If the nerves running from the spinal cord to the muscles are damaged (denervation), standard FES cycling will not work and a specialised approach is needed.
- Spinal cord injury has the strongest evidence base. FES cycling is effective for both complete and incomplete injuries, with the potential for functional recovery being greater in incomplete injuries.
- Stroke survivors can benefit from FES cycling, particularly in promoting neuroplasticity, improving muscle strength, and reducing spasticity. Early intervention offers the best opportunity, but gains are possible at any stage.
- Multiple sclerosis responds well to FES cycling, though the programme needs to accommodate the condition's fluctuating nature.
- Cerebral palsy in children and young people shows encouraging results, with improvements in muscle size, power output, and spasticity.
- Parkinson's disease generally benefits from cycling exercise, and FES cycling can supplement voluntary effort to enable more intensive workouts. Specific FES cycling research for Parkinson's is limited.
- Transverse myelitis is generally treatable with FES cycling, but the possibility of denervation must be assessed.
- Cauda equina syndrome involves lower motor neuron damage. Standard FES cycling is not effective; specialised denervation stimulation is required.
- Individual assessment is essential. No two people respond in the same way, and your programme should be tailored to your specific condition, goals, and capabilities.
In Chapter 6, we look honestly at what FES cycling cannot do, including the limitations you should be aware of before committing to a programme.