What You Will Learn
FES cycling did not appear overnight. It is the product of decades of scientific curiosity, engineering innovation, and clinical persistence. In this chapter, we trace the story from the earliest experiments with electrical stimulation of muscle through to the commercial systems available today. Understanding this history helps to appreciate that FES cycling is not an unproven novelty; it is a technology built on a solid foundation of research stretching back over sixty years.
Early Pioneers: From Electrical Stimulation to FES Cycling
The idea that electricity can make muscles contract has been known for a remarkably long time. In the 1790s, the Italian scientist Luigi Galvani demonstrated that electrical stimulation of a frog's sciatic nerve produced a contraction of the leg. This observation, and the famous debate it sparked with Alessandro Volta, laid the foundations for what eventually became the field of electrotherapy.
By the 1870s, the French physician Guillaume Duchenne was using electrical stimulation to produce muscle contractions in patients with paralysis, including attempts to initiate standing in people with paraplegia. The technology of the day was primitive by modern standards, but the principle was established: muscles could be made to contract using externally applied electrical energy, even when the person had no voluntary control over them.
The modern era of functional electrical stimulation began in 1960 when Adrian Kantrowitz demonstrated paraplegic standing by applying continuous surface FES to the quadriceps and gluteus maximus muscles of a patient with a complete spinal cord injury. Stimulation of these muscle groups produced full extension of the lower limbs and enabled a rudimentary form of upright posture. This work established the practical viability of FES in living humans and introduced two enduring design principles: the use of surface electrodes to deliver stimulation to large lower-limb muscle groups, and the exploitation of knee extension as the biomechanical cornerstone of any FES-driven upright activity. Kantrowitz’s demonstration is widely cited as the first application of FES to a paraplegic patient in the clinical literature.
The specific story of FES cycling begins in the early 1960s. In 1961, Lieberson and colleagues published research on the use of electrical stimulation to elicit functional movements in people with paralysis. This was among the earliest research to consider electrical stimulation not simply as a way to make a muscle twitch, but as a means of producing coordinated, purposeful, functional movement.
The most transformative technology for FES cycling was the microprocessor. By the late 1970s and early 1980s, compact microcomputers capable of real-time stimulation control had become sufficiently affordable for research use. The ability to read a sensor, perform a calculation, and immediately adjust a stimulation output in real time was the missing ingredient that transformed multi-channel FES from a laboratory curiosity into a viable cycling system. Without the microprocessor, the timing of muscle activation we have described cannot adapt to changes in the rider’s cadence, fatigue state, or mechanical load, making sustained rhythmic cycling practically impossible.
Running in parallel with the electrotherapy work was an ambitious effort to restore walking in paraplegic patients through multi-channel FES, pursued especially at the Cleveland VA Medical Centre by researchers including Marsolais and Kobetic. Their programme ultimately proved that FES-driven ambulation was physiologically possible but mechanically extremely demanding. The resulting systems were difficult to use and impractical for most patients. This relative failure of FES walking as a widespread clinical tool motivated researchers to seek a simpler, more mechanically constrained task that could still deliver meaningful health benefits. Cycling, with its constrained movements and lower risk of falls, emerged as an elegant solution.
In the early 1980s, when Jerrold Petrofsky and his team demonstrated that people with complete spinal cord injuries could pedal a cycle ergometer using controlled, sequential stimulation of the major leg muscles. By stimulating the quadriceps, hamstrings, and gluteal muscles in a coordinated pattern timed to the rotation of the pedals, Petrofsky showed that genuine cycling was possible despite complete paralysis. This was the proof of concept that launched FES cycling as a field of research and, eventually, as a practical rehabilitation tool.
Building on the 1983 tricycle concept, Petrofsky and Phillips published a comprehensive review in 1984 in Central Nervous System Trauma, summarising the full scope of their research programme. The review covered the system design, leg-training results (boasting of gains in muscular strength and mass in paraplegic and quadriplegic subjects), cycle-ergometer exercise results (improved muscular endurance and cardiovascular responses), and thermoregulatory findings. Importantly, this paper formalised the conceptual transition from the outdoor tricycle, conceived partly as a mobility device, to the stationary ergometer models we see today.
The Development of Closed-Loop Systems
Early FES cycling systems used what engineers call open-loop control. With such a system, there is no connection (feedback) of the state of the output available at the input. There is a 'cause' (stimulation of the muscles) and an 'effect' (the muscles contract to pedal the bike), but this doesn't provide the best solution when the process you are trying to control tends to change its behaviour. For example, If the rider's muscles fatigued or a spasm disrupted the cycling motion, the system could not adapt. The stimulation was delivered according to a fixed, pre-programmed pattern regardless of what was actually happening at the pedals.
The important advance that followed was the development of closed-loop control systems. In a closed-loop system, the stimulator could, for example, continuously monitor pedal position and speed and use this information to adjust stimulation in real time. If a muscle group is tiring, the system can compensate. If the pedals slow down, the stimulation pattern adapts. This made FES cycling far more practical, safer, and more effective for everyday use.
Research groups around the world contributed to this development. Kenneth Hunt and his colleagues, for example, carried out significant work on optimising the control and efficiency of FES cycling systems, helping to refine the algorithms that made closed-loop cycling reliable enough for use in homes and clinics rather than only in research laboratories.
Commercial Systems and the Growth of FES Cycling
The transition from research laboratories to commercial products took time. Developing a system that was safe, effective, and practical enough for regular home use was a considerable engineering and regulatory challenge.
ERGYS (Therapeutic Alliances Inc) was one of the earliest commercial FES cycling systems with FDA clearance in 1984. Designed for clinic use, ERGYS established the concept of a dedicated FES ergometer and helped to demonstrate the clinical value of electrically stimulated cycling in a rehabilitation setting. It was an important step in moving FES cycling from the research bench to clinical practice. The ERGYS format established what became the de facto standard FES cycle architecture: an integrated chair-and-pedal mechanism, surface electrodes applied to the thighs and buttocks, a programmable stimulator with individual-channel profiles, and a motorised flywheel that provides passive assistance when the stimulated muscles cannot generate sufficient torque to maintain cadence. This hybrid motor-plus-FES design is universal in clinical FES cycling systems. it's a product that remains in active production, but as far as we know, it is only available in the USA.
RT300 (Restorative Therapies) represented a significant advance in making FES cycling accessible. The system received its CE mark as a Class IIa medical device in 2005, the same year it received FDA clearance in the United States. It was introduced to the UK around 2007 to 2008 and was probably the first widely available commercial FES cycling system in this country. The RT300 was designed for both clinic and home use, and its arrival meant that for the first time, people in the UK could realistically access FES cycling outside of a research programme. Restorative Therapies played an important role in establishing the UK market for this technology.
RehaMove (Hasomed) was introduced around the same period, approximately 2007, taking a different approach by integrating a programmable FES stimulator with established passive/active bikes from the MOTOmed range. They also introduced a version based on a recumbent bike.
This meant that users could benefit from an exercise bike that was already well proven for passive cycling, with the addition of synchronised electrical stimulation. The RehaMove system has become widely used in the UK, and Anatomical Concepts has worked with it for the better part of two decades, supporting hundreds of clients in their homes and clinical settings.
BerkelBike, a Dutch system, took a different direction entirely by combining FES with a recumbent tricycle designed for outdoor use. This opened up the possibility of FES-powered cycling not just as a stationary exercise modality but as a means of getting outdoors and covering real ground, an appealing prospect for many users.
MyoCycle (Myolyn) is a more recent entrant, available primarily in the United States. It represents the continued evolution of the field, with each new system bringing improvements in usability, affordability, or clinical capability.
Stim2Go (Pajunk, developed by SensorStim Neurotechnology) represents the current generation and a notable shift in philosophy. Rather than integrating the stimulator with a specific bike, Stim2Go is a standalone device with built-in motion sensors. It can be attached to the user and paired with virtually any passive/active bike. This means that someone who already owns a THERA-Trainer or MOTOmed bike can add FES cycling capability without replacing their existing equipment. It also means the stimulator can be used for applications beyond cycling, including other forms of FES-enhanced exercise and transcutaneous spinal cord stimulation. By decoupling the stimulator from the bike, Stim2Go has the potential to make FES cycling accessible to a much wider group of people than has been the case previously.
FES Cycling Around the World Today
FES cycling is now used in homes, hospitals, and rehabilitation centres across the world. The strongest evidence base is in spinal cord injury, but its use for stroke, multiple sclerosis, Parkinson's disease, cerebral palsy, and other neurological conditions continues to grow.
In the United Kingdom, adoption has been driven significantly by medico-legal funding. Many people with spinal cord injuries sustained through accidents have been able to access FES cycling systems as part of their compensation settlement. This has meant that the UK has a relatively large population of home-based FES cycling users compared with many other countries. However, it has also meant that access has been uneven: those without medico-legal funding have often found the cost prohibitive.
The cost of FES cycling systems has historically been a barrier to wider adoption. Complete systems have typically cost many thousands of pounds, placing them beyond the reach of many who could benefit. Newer approaches, particularly the ability to add FES capability to an existing bike rather than purchasing a fully integrated system, are beginning to change this picture. We discuss funding and access in detail in Chapter 12.
Chapter Summary
- Electrical stimulation of muscle has been understood since the 1790s. The specific application to cycling began with Lieberson in the 1960s and was proven by Petrofsky in the early 1980s.
- The development of closed-loop systems, where the stimulator monitors and responds to pedal position in real time, made FES cycling practical for everyday use.
- Commercial systems including the ERGYS, RT300, RehaMove, BerkelBike, MyoCycle, and Stim2Go have each contributed to making FES cycling more accessible, more capable, and more widely used.
- In the UK, FES cycling has been most commonly accessed through medico-legal funding, although newer, more flexible systems are beginning to broaden access.
- The technology is well established, with a research pedigree spanning over sixty years and a growing global user base.
In Chapter 4, we move from the history of FES cycling to its evidence base: what does the research tell us about the benefits?