Benefits of FES Cycling: The Evidence

What You Will Learn

In this chapter, we look at the evidence for the health benefits of FES cycling. We will cover what the research tells us about muscle strength and size, cardiovascular fitness, bone health, spasticity, circulation, neuroplasticity, and psychological well-being. We also explain how FES cycling compares with passive cycling and why the distinction matters. By the end of this chapter, you should have a clear understanding of what FES cycling can realistically achieve and where the evidence is strong, emerging, or still uncertain.

Why Evidence Matters

If you are considering FES cycling, or have already started, you deserve to know what the research actually shows. This is not a field short of claims. Various companies and individuals will tell you what their products can do, and it can be difficult to know whether the differences between the systems are of practical significance.

Our approach has always been to let the evidence lead. Where the evidence is strong, we will say so. Where it is promising but incomplete, we will say that too. You are an intelligent adult capable of weighing the evidence and making informed decisions, and that is the spirit in which this chapter is written.

The research into FES cycling spans more than three decades. Much of it has been conducted in spinal cord injury populations, though there is a growing body of work in stroke, multiple sclerosis, cerebral palsy, and other neurological conditions. We will draw on this literature throughout and, where helpful, point you to specific studies if you wish to explore further.

Muscle Strength and Size

One of the most visible benefits of FES cycling is that it builds muscle. After a spinal cord injury or other neurological condition, muscles that are no longer being used will atrophy. They lose mass and strength, and over time, their tissue quality changes. This is not just a cosmetic concern. Loss of muscle mass has metabolic consequences: it affects how your body handles blood sugar, increases the risk of diabetes and cardiovascular disease, and reduces the overall health of the tissues in your limbs.

FES cycling directly addresses this because, as we explained in Chapter 1, it produces genuine active muscle contractions. When muscles contract against resistance, they adapt. They get larger and stronger. This is the same basic training principle that applies to any form of resistance exercise, whether you are a gym enthusiast or a person with a spinal cord injury using electrical stimulation.

The research supports this clearly. Studies in adults with chronic spinal cord injury have demonstrated increases of 19 to 30% in thigh muscle cross-sectional area after 8 to 12 weeks of FES cycling. In children with spinal cord injury, 6 months of FES cycling increased quadriceps cross-sectional area by 15-20% and reduced intramuscular fat by 53%. These are meaningful changes.

By comparison, passive cycling (using a motorised bike without stimulation) shows negligible effects on muscle size: typically less than 1% change. This is the fundamental difference. Passive cycling moves your legs, but because the muscles are not actively contracting, there is no stimulus for them to grow or strengthen.

What you are likely to notice is that your muscles fatigue rapidly in the early weeks. This is entirely normal because after a period of disuse, the muscle fibres have changed in ways that make them more fatigable. With regular training, this improves. Over time, sessions can get longer, the power you generate can increase, and the visible size of your muscles can change. Many of our clients report seeing and feeling the difference in their legs within a few weeks.

Cardiovascular Fitness

Cardiovascular health is one of the most important long-term concerns after a spinal cord injury. When large muscle groups in the legs can no longer be exercised, the body loses a significant part of its capacity to raise heart rate and maintain the kind of fitness that protects against heart disease, stroke, and metabolic conditions. The risk of cardiovascular disease is substantially higher in the spinal cord injury population than in the general population, and it is one of the leading causes of death in the years after injury.

FES cycling provides a way to actively exercise the large muscle groups of the legs, even when voluntary control has been lost. This raises heart rate, increases oxygen consumption, and places a genuine aerobic demand on the cardiovascular system. Research has shown that FES cycling can increase peak oxygen uptake (a key measure of aerobic fitness, often written as VO2peak) by 14 to 29% in people with spinal cord injury.

Beyond the heart itself, the "vascular" part of the cardiovascular system matters enormously. After a spinal cord injury, blood vessels in the paralysed limbs undergo structural changes: they become narrower, and resistance to blood flow increases. Sometimes clients will notice swelling in the feet or lower legs, which is a reminder that circulation is not just outward from the heart but also back to the heart. FES cycling can remedy this swelling by stimulating the tibialis anterior and gastrocnemius/soleus muscles. Research by Hopman and colleagues demonstrated that this increased vascular resistance is reversible with training using electrical stimulation of the leg muscles. FES cycling, by repeatedly contracting and relaxing the leg muscles, acts as a muscle pump that drives blood through the limbs, improving circulation and encouraging the blood vessels to adapt in beneficial ways.

Physical activity guidelines developed specifically for the spinal cord injury population recommend at least 20 minutes of moderate-to-vigorous aerobic activity twice weekly for fitness benefits, and at least 30 minutes three times per week for broader cardiometabolic health. We would say that greater commitment is likely to be more effective if time can be made for exercise. FES cycling is one of the most practical ways to meet these guidelines when leg paralysis prevents conventional exercise.

Bone Health

Bone is a living tissue that responds to the loads placed upon it. When you stand, walk, and exercise, your bones experience mechanical forces that signal them to maintain or increase their density. After a spinal cord injury, the loss of standing and weight-bearing activity leads to a progressive decline in bone mineral density. As a rough guide, around 40% of bone density can be lost within the first three years, with the decline typically plateauing around seven years post-injury. Weakened bones increase the risk of fractures, sometimes from surprisingly minor forces.

FES cycling generates active muscle contractions that pull on the bones during the pedalling action. This repetitive loading provides a mechanical stimulus that can help preserve bone density. Research has shown improvements in bone mineral density at the distal femur (the lower end of the thigh bone, near the knee) with FES cycling. In children with spinal cord injury, six months of FES cycling produced a 46% increase in distal femur bone mineral density, compared with just 2.7% from passive cycling alone.

There are some important caveats. The evidence on bone density is mixed: some studies have found significant benefits, whilst others have found more modest effects. The key factor appears to be the intensity of the exercise. If the muscle contractions do not generate sufficient load on the bones, the stimulus may not be sufficient to drive meaningful change. This is one reason why it is important to progress the resistance and intensity of your FES cycling programme over time, rather than staying at the same low level indefinitely.

Early intervention also matters. It may be possible to preserve bone density, but not to reverse a decline that has already occurred. If FES cycling is started in the months following injury, the chances of maintaining bone strength are better than if you begin years later when significant bone loss has already taken place.

The only reliable way to know the state of your bone health is through a DEXA scan, which uses low-dose X-rays to measure bone density. Your clinical team may recommend one before you begin FES cycling, particularly if your injury is not recent.

Spasticity

Spasticity (the involuntary stiffness and tightness of muscles) is a common and often troublesome consequence of spinal cord injury, stroke, and other neurological conditions. It can range from a mild background tightness to forceful spasms that interfere with daily life, sleep, and positioning.

FES cycling has been shown to reduce spasticity, and the evidence here is reasonably strong. A meta-analysis of studies involving 20 or more sessions of FES cycling found a reduction in Modified Ashworth Scale scores (a standard measure of spasticity) of almost one full point. This may not sound dramatic, but in clinical terms, it represents a meaningful improvement: the difference between a limb that resists movement substantially and one that can be moved more freely.

The mechanism is thought to involve several factors. Rhythmic muscle contractions during cycling help restore a normal pattern of inhibition in the spinal cord reflexes that drive spasticity. FES also activates Renshaw cells, which dampen excessive motor neuron activity. In practical terms, many of our clients notice that their legs feel looser and more relaxed after a cycling session, and with regular use, this benefit becomes more sustained.

Research has shown that people with spinal cord injury can retain reduced spasticity for up to six months after a course of FES cycling, with improvements in pendulum test scores (a measure of how freely the lower leg swings) persisting well beyond individual sessions. By contrast, passive cycling produces only a transient reduction in spasticity that typically does not last beyond 24 hours.

If you have troublesome spasticity, it is worth noting that how FES cycling is set up can make a difference. Using lower stimulation frequencies at the start of a session can help settle spasm before the main exercise phase begins. We discuss this in more detail in Chapter 9.

Circulation and Skin Health

Poor circulation in the legs is a common problem after spinal cord injury. Without regular muscle contractions, blood tends to pool in the lower limbs as we mentioned above, and the normal "muscle pump" that assists venous return (the flow of blood back toward the heart) is compromised. This increases the risk of deep vein thrombosis, oedema (swelling), and slow wound healing. Skin breakdown and pressure ulcers are among the most frequent and serious complications of spinal cord injury.

FES cycling directly activates the muscle pump. Each time the leg muscles contract during pedalling, they compress the veins and push blood back toward the heart. This improves circulation in the lower limbs and reduces the risk of blood pooling. Research has demonstrated that even a short course of FES training (as few as four sessions over two weeks) can increase blood flow in the legs and enlarge the diameter of the femoral artery.

For skin health, the improved circulation matters in a very practical way. Better blood flow means better delivery of oxygen and nutrients to the tissues and more efficient removal of waste products. This creates a healthier environment for the skin and underlying tissues, reducing the risk of pressure ulcers and helping minor wounds heal more quickly. Several of our clients with slow-to-heal skin issues on their lower legs have reported improvements after starting regular FES cycling.

Neuroplasticity

Neuroplasticity refers to the nervous system's ability to reorganise itself by forming new connections between neurons. It is, in essence, the biological basis of learning and recovery. For a long time, it was assumed that the adult nervous system was fixed and incapable of meaningful change after injury. We now know this is not the case.

FES cycling supports neuroplasticity in several ways. The repeated, rhythmic activation of specific muscles sends sensory signals back to the spinal cord and brain. These signals help maintain and potentially strengthen the neural pathways involved in movement. When FES is combined with task-specific, repetitive exercise (which is exactly what FES cycling provides), the conditions are well-suited for neuroplastic change.

For people with incomplete spinal cord injury or stroke, where some neural pathways remain intact, this is particularly relevant. The repeated stimulation of motor and sensory pathways may help the nervous system find new routes for signals, potentially contributing to some functional recovery over time. Research has shown that FES can induce cortical reorganisation (changes in the brain's motor areas) and strengthen neural pathways through a process known as long-term potentiation.

We should be honest about the limits of current knowledge. Neuroplasticity is a genuine phenomenon with solid science behind it, but the extent to which it translates into functional recovery varies widely among individuals and depends on factors such as the nature of the injury, the time since injury, and the intensity of training. We are not promising miracles. What we can say is that FES cycling provides a form of exercise that aligns well with the principles neuroscience tells us are important for promoting beneficial neuroplastic change: repetition, intensity, task specificity, and consistency.

With our Stim2go system, we can deliver transcutaneous spinal cord stimulation (tSCS) during FES cycling and this can have interesting effects as we will discuss later.

Psychological Wellbeing

The physical benefits of FES cycling are well documented, but we should not overlook the psychological dimension. Living with a spinal cord injury or other neurological condition is, for most people, profoundly challenging. The loss of physical ability, independence, and previous identity can contribute to depression, anxiety, and a diminished sense of self-worth.

Exercise has been consistently shown to improve mental health outcomes: it releases endorphins, reduces stress hormones, and provides a sense of achievement and routine. For people who have lost the ability to exercise conventionally, FES cycling offers more than just physical benefits. It provides an activity that feels like genuine exercise, because it is. Seeing your muscles contract, feeling your heart rate rise, watching power output numbers climb over the weeks: these are tangible markers of progress that matter psychologically as well as physically. Many clients like the idea of their legs looking and feeling toned and "normal".

Many of our clients describe a sense of purpose and control that comes from their FES cycling programme. In a situation where so much feels beyond their control, having something they can do actively for their own health is important. We have worked with people who have told us that FES cycling changed their outlook more than any other single intervention in their rehabilitation.

We do not have the same volume of controlled research on the psychological benefits as we do for the physical ones, but the consistent testimony from our clients over many years leaves us in no doubt that this dimension is real and significant.

FES Cycling Compared with Passive Cycling

Throughout this chapter, we have noted where FES cycling produces benefits that passive cycling does not. It is worth bringing this comparison together clearly, because it is one of the most common questions we are asked: "Why do I need FES? I already have a passive bike."

The answer is that passive cycling and FES cycling are fundamentally different interventions. A passive bike moves your legs through a range of motion using a motor. This is often useful: it maintains joint flexibility, provides temporary relief from spasticity, and may modestly improve circulation. If a passive bike is all that is available to you, it is certainly better than doing nothing.

However, because your muscles are not actively contracting during passive cycling, there is no stimulus for muscle growth, no meaningful cardiovascular demand, no significant bone loading, and no sustained reduction in spasticity. The research consistently shows that adding FES to cycling yields benefits across all these domains that passive cycling alone does not achieve.

The following table summarises the key differences based on the research evidence:

The key barrier to FES cycling has historically been cost, with FES cycling systems costing considerably more than a passive bike alone. Newer products are beginning to change this equation by allowing a separate stimulator to be paired with an existing passive bike, reducing the overall investment. We discuss equipment options in Chapter 8.

Clients recovering from a stroke, MS or with an incomplete spinal cord injury may feel that using a passive/active bike will provide sufficient exercise and that FES would not add anything useful for them. This may be true but a key issue is how long they are truly able to exercise actively? If after a few minutes, fatigue is limiting their ability to pedal for themselves, it becomes very hard to exercise long enough to produce a progressive benefit. Adding FES into the mix allows such individuals to work as much as they can with their own abilities and yet know that FES can support them to work longer and harder.

How Much Exercise Is Enough?

One of the questions we hear frequently is: how often do I need to cycle, and for how long? The honest answer is that we do not have a precise formula that applies to everyone. What we do know is that the dose of exercise matters. The first rule of exercise, as we often say, is that you have to turn up and do it.

Research suggests that a minimum of two to three sessions per week, each lasting 20 to 30 minutes of active cycling, is needed to see cardiovascular and musculoskeletal benefits. For spasticity reduction, the evidence points toward 20 or more sessions being required for clinically meaningful effects. More frequent and longer sessions generally produce greater benefits, but this has to be balanced against what is practical and sustainable for you in your daily life. No one can spend all day exercising and disability often comes with daily routines that must be performed.

In the early weeks, your sessions may be shorter because your muscles fatigue quickly. The priority at this stage is consistency: establishing the habit, building tolerance, and allowing your muscles to adapt. Over time, sessions can be lengthened and the intensity increased. We discuss programme progression in detail in Chapter 10.

The most important thing is long-term commitment. FES cycling is not a short-term fix. Like all forms of exercise, its benefits depend on sustained, regular use. The people who get the most from it are those who make it part of their routine, week after week, month after month.

Chapter Summary

• FES cycling builds muscle mass and strength in paralysed or weakened limbs. Increases of 19 to 30% in thigh muscle size have been demonstrated in 8 to 12 weeks.
• Cardiovascular fitness improves significantly, with peak oxygen uptake increasing by 14 to 29%. This is one of the most important long-term health benefits after spinal cord injury.
• Bone health can be preserved or improved, particularly with early intervention and sufficient exercise intensity.
• Spasticity is reduced meaningfully, with benefits that persist beyond individual sessions and can be sustained for months.
• Circulation in the lower limbs is improved through the muscle pump effect, supporting skin health and reducing the risk of pressure ulcers and deep vein thrombosis.
• Neuroplasticity is supported by the repetitive, task-specific nature of FES cycling, though the degree of functional recovery varies between individuals.
• Psychological wellbeing is consistently reported by users, with FES cycling providing a sense of achievement, purpose, and control.
• FES cycling outperforms passive cycling across all major health outcomes. Passive cycling has value for joint mobility, but it does not produce the metabolic, cardiovascular, or musculoskeletal benefits of active exercise.
• Consistency and long-term commitment are essential. The benefits of FES cycling depend on regular, sustained use.

In Chapter 5, we look at the evidence for FES cycling across specific conditions: spinal cord injury, stroke, multiple sclerosis, cerebral palsy, and others.