What FES Cycling Cannot Do

What You Will Learn

In Chapters 4 and 5, we set out what FES cycling can achieve and for whom. This chapter is the honest counterpart. Here we explain the limitations of FES cycling: what it cannot do, where the evidence falls short, the contraindications that may prevent its use, and the practical realities that can frustrate even the most committed user. We believe you deserve this information before you commit your time, energy, and money to a programme. Understanding the limitations is not a reason to avoid FES cycling; it is the foundation for realistic expectations and, ultimately, for getting the most from it.

FES Cycling Will Not Restore Walking

This is the single most important expectation to address. For the majority of people with a complete spinal cord injury, FES cycling will not enable them to walk again. It is an exercise modality, not a cure.

We raise this first because it is the hope that many people carry when they first hear about FES cycling. The idea that electrical stimulation might somehow reconnect what has been disconnected is understandable, but for most people with complete injuries, it is not realistic with current technology. FES cycling produces active muscle contractions that deliver genuine health benefits (as we described in Chapter 4), but the contractions are produced by the stimulator, not by restored voluntary control. When the stimulator is switched off, the muscles are once again under no voluntary command.

For people with incomplete spinal cord injuries or stroke, the picture is more nuanced. Some individuals do experience improvements in walking ability following FES cycling programmes, as we discussed in Chapter 5. However, these gains are variable, often modest, and not guaranteed. If anyone promises you that FES cycling will get you walking, treat that claim with considerable scepticism.

The honest position is this: FES cycling is a powerful tool for maintaining and improving long-term health. It is not a pathway to functional recovery for most people with complete injuries, and for those with incomplete injuries, any functional gains should be seen as a welcome bonus rather than an expected outcome.

FES Cycling Does Not Work for Denervated Muscle

We covered this in Chapter 5, but it bears repeating here because it is a fundamental limitation. If the lower motor neurons supplying your muscles are damaged (as in cauda equina syndrome, some lower spinal injuries, and certain peripheral nerve conditions), your muscles are denervated and will not respond to the type of electrical stimulation used in FES cycling.

This is not a shortcoming of any particular product. It is a matter of physics and physiology. The electrical pulses used in FES cycling are designed to stimulate nerves. If the nerves are absent or non-functional, there is nothing for the stimulation to act upon. A different form of electrical stimulation, with much longer pulse widths and other parameters, is needed to directly stimulate denervated muscle fibres. This requires specialist equipment and is covered in our companion book. Some products, such as the RT300 and Stim2Go, can deliver pulse widths longer than standard, but they are unlikely to be effective in cases of complete denervation.

If you are uncertain whether your muscles are innervated or denervated, a clinical assessment that includes testing your muscles' response to electrical stimulation will provide the answer. This should always be carried out before you invest in an FES cycling system.

The Efficiency Problem

FES cycling is considerably less efficient than voluntary cycling. Research by Kjaer and colleagues demonstrated that to achieve the same oxygen consumption, FES cycling produced less than 40 watts of mechanical power compared with approximately 120 watts during voluntary cycling. In other words, FES cycling is roughly three times less efficient in converting metabolic effort into mechanical work.

This matters in practical terms. It means that the amount of physical work (power, distance, resistance) you can achieve with FES cycling will be lower than a person of similar fitness could achieve by pedalling voluntarily. It also means your muscles will fatigue more quickly, particularly in the early weeks.

The reasons for this are well understood. Two main factors contribute: unfavourable biomechanics (the relatively crude way in which FES recruits muscle groups compared with the brain's precise coordination) and non-physiological fibre recruitment (FES tends to activate fast-twitch, fatigable fibres first, which is the opposite of normal voluntary recruitment).

Does this mean FES cycling is not worthwhile? Not at all. The health benefits we described in Chapter 4 are achievable despite this inefficiency. But it does mean you should not compare your FES cycling performance with that of an able-bodied cyclist, and you should not be discouraged by initially low power outputs or short session durations. The system is inherently less efficient, and improvement comes with consistent training over weeks and months.

Benefits Reverse When You Stop

This is true of all forms of exercise, but it is worth stating clearly for FES cycling. The benefits you gain from regular use will diminish if you stop.

Research on vascular adaptations provides a striking illustration. A study by Thijssen and colleagues showed that after six weeks of FES training, improvements in blood flow, femoral artery diameter, and vascular resistance were all measurable. After just one week of stopping training, these vascular gains had returned to their pre-training values.

Muscle mass, cardiovascular fitness, and bone density all follow a similar pattern: they improve with regular training and decline with inactivity. This is not unique to FES cycling; it is a fundamental principle of exercise physiology. But it has practical implications. FES cycling is a long-term commitment. If you are considering it as a short-term intervention with lasting effects, you should know that the benefits will not persist once you stop.

The first rule of exercise, as we often say, is that you have to turn up and do it. The second rule is that you have to keep doing it.

Contraindications: When FES Cycling Should Not Be Used

Like all medical devices, FES cycling systems have contraindications: situations in which the treatment should not be used because the risks outweigh the benefits. Every manufacturer will state these clearly, and your clinical team should assess you against them before you begin.

Absolute Contraindications

These are situations in which FES cycling should not be used under any circumstances:

• Cardiac pacemakers, implanted defibrillators, or other active electronic implants. The electrical fields generated by the stimulator could potentially interfere with these devices. This is a firm contraindication across all FES products.
• Active cancer or malignant tumours in the area to be stimulated. There is a theoretical risk that electrical stimulation could influence tumour growth or blood supply.
• Pregnancy. The effects of electrical stimulation on a developing foetus are unknown, and the precautionary principle applies.
• Active deep vein thrombosis (DVT) or thrombophlebitis. Muscle contractions could potentially dislodge a clot. If you have a known or suspected DVT, FES cycling must wait until this has been treated and resolved.
• Uncontrolled epilepsy. Although the risk is considered low, electrical stimulation is generally avoided in people with unstable epilepsy.
• Active fractures in the limbs to be exercised. The forces generated by muscle contraction could displace a fracture.

Relative Contraindications

These are situations where FES cycling may still be possible but requires careful clinical judgement in which the potential risks are weighed against the likely benefits:

• Metal implants (plates, screws, joint replacements) near the electrode sites. Research suggests that passive metal implants generally do not pose a safety concern for surface electrical stimulation, as no significant heating has been demonstrated. However, the manufacturer's guidance should be followed, and your clinician should assess the specific situation.
• Severe joint contractures. If your knees or hips cannot achieve sufficient range of motion to allow pedalling, FES cycling may not be feasible until the contractures have been addressed.
• Significant skin damage, open wounds, or active infection at the electrode sites. Electrodes should not be placed over compromised skin.
• Autonomic dysreflexia risk. For people with spinal cord injuries above T6, FES cycling can occasionally trigger autonomic dysreflexia (a sudden, dangerous rise in blood pressure). This is manageable with proper monitoring and is covered in detail in Chapter 9, but it requires awareness and preparation.
• Severe osteoporosis. If bone density is severely compromised, there is a theoretical risk that forceful muscle contractions could cause a fracture. A DEXA scan may be recommended before starting.

The lists above are not exhaustive, and individual products may have additional specific contraindications. A thorough clinical assessment before you begin will identify any issues relevant to you.

FES Cycling Is Not a Passive Activity

Despite the name "passive/active bike" for the cycling equipment, FES cycling itself demands active engagement. The stimulator produces the muscle contractions, but the person using the system (and, initially at least, their clinical support team) must manage the session: ensuring correct electrode placement, adjusting stimulation parameters, monitoring responses, and progressing the programme over time.

This is not something you simply switch on and forget about. In the early weeks, sessions require supervision and adjustment. Even once you are trained and independent, each session involves setup time (typically 10 minutes for electrode placement and system configuration) in addition to the cycling time itself. Including setup and cool-down, a 30-minute active cycling session may take 45 minutes in total.

Some people find this manageable; others find it a significant demand on their daily routine, particularly when managing the other aspects of life with a disability. It is worth being realistic about the time commitment before you begin.

FES Cycling Cannot Replace a Comprehensive Rehabilitation Programme

FES cycling is one component of a broader approach to health and rehabilitation. It is excellent for cardiovascular fitness, muscle conditioning, spasticity management, and circulation, but it does not typically address every need.

It does not, for example, provide:

• Standing or weight-bearing exercise. FES cycling is performed seated. While the muscle contractions do load the bones to some extent, they do not replicate the benefits of standing, which is important for bone health, bowel function, and psychological well-being. Standing programmes, standing frames, or devices such as the Tek RMD address this need separately.
• Upper body conditioning. Standard FES cycling targets the legs. Some systems support arm exercise with stimulation, but if your upper body is also affected, a separate programme will be needed.
• Fine motor skills or hand function. FES cycling does not address weakness in the hands or arms. Other forms of electrical stimulation and rehabilitation technology exist for this purpose.
• Bladder and bowel management. These are critical aspects of life after spinal cord injury that FES cycling does not directly address, though improved fitness and regular exercise may have indirect benefits.
• Psychological support. While many users report improved well-being from FES cycling (as we discussed in Chapter 4), it is not a substitute for professional psychological support if this is needed.

The most effective approach is usually one that combines FES cycling with other forms of exercise, therapy, and support tailored to your individual needs.

The Cost Barrier

We would be dishonest if we did not acknowledge that cost is a significant limitation. Complete FES cycling systems have historically cost (sometimes much) more than £10,000, including hardware, professional assessment, individual configuration, training, and ongoing support. This is a substantial investment, and for many people it is simply unaffordable.

In the UK, the majority of our FES cycling clients have been able to access the technology through medico-legal funding following a catastrophic injury. For people with stroke, multiple sclerosis, cerebral palsy, or Parkinson's disease, this funding pathway is rarely available. The NHS does not routinely prescribe FES cycling systems, and charitable funding, while sometimes available, is limited and competitive.

Newer products are beginning to change this picture. Universal stimulator systems (such as the Stim2go) that can be paired with an existing passive bike, rather than requiring a dedicated integrated system, reduce overall cost. But even so, the combination of equipment, assessment, and ongoing support represents a significant expense.

We discuss equipment options, costs, and funding pathways in more detail in Chapter 8.

Variability of Response

One of the most frustrating aspects of FES cycling is that people respond differently. Two individuals with apparently similar injuries, using the same equipment and following the same programme, may achieve quite different results. One may see rapid muscle growth and improved fitness; the other may progress more slowly.

This variability is a feature of all rehabilitation, not just FES cycling. It reflects the complexity of the human body and the influence of factors such as the exact nature of the neurological injury, the time since injury, age, overall health, nutrition, and individual physiology.

We have learned from experience that the most reliable predictor of success is not the severity of the injury but the consistency and commitment of the person using the system. Those who make FES cycling a regular part of their routine, week after week, are the ones who see the greatest benefits. But even with the best commitment, we cannot guarantee a specific outcome for any individual.

The Evidence Has Gaps

Throughout Chapters 4 and 5, we presented the research evidence, noting where it is strong and where it is limited. It is worth gathering those caveats together here.

• Most research has been conducted in spinal cord injury populations. The evidence for stroke, MS, cerebral palsy, and Parkinson's is growing but smaller.
• Many studies have small sample sizes. This is common in rehabilitation research and makes it difficult to draw firm conclusions.
• Long-term studies are limited. We know what happens over weeks and months, but there is less data on outcomes over years of use.
• The optimal "dose" remains uncertain. We know that more exercise generally produces better results, but the precise frequency, duration, and intensity needed for specific outcomes have not been definitively established.
• Research on bone density is mixed. Some studies show significant benefits; others show more modest effects. The intensity of exercise appears to be a key factor.
• Psychological benefits are reported consistently by users but have not been studied with the same rigour as physical outcomes.

None of this means FES cycling does not work. The weight of evidence across three decades is clearly positive. But it does mean that we should be honest about the limits of what we know.

Chapter Summary

• FES cycling will not restore walking for most people with complete spinal cord injuries. It is an exercise tool, not a cure.
• It does not work for denervated muscle. If your lower motor neurons are damaged, a different form of electrical stimulation is required.
• FES cycling is approximately three times less efficient than voluntary cycling. Initial power outputs will be low, and muscles will fatigue quickly.
• Benefits reverse when you stop training. FES cycling is a long-term commitment, not a short-term fix.
• Contraindications exist, including cardiac pacemakers, active DVT, pregnancy, and active fractures. A clinical assessment is essential before starting.
• FES cycling requires active engagement: electrode placement, parameter adjustment, and session management take time and attention.
• It cannot replace a comprehensive rehabilitation programme. Standing exercise, upper body conditioning, and other needs must be addressed separately.
• Cost remains a significant barrier, though newer products are making FES cycling more accessible.
• Responses vary between individuals. Consistency of use is the most reliable predictor of benefit.
• The evidence base is substantial but has gaps, particularly for conditions other than spinal cord injury and for long-term outcomes.

Despite these limitations, FES cycling remains one of the most effective exercise options available for people with neurological conditions affecting the lower limbs. Understanding what it cannot do is the best preparation for making the most of what it can.

In Part 3, we move from the evidence to the practice: getting started with FES cycling, the equipment involved, and what your sessions will look like.