What You Will Learn
In this chapter, we walk through what actually happens during an FES cycling session from the moment you switch the system on to the moment you step off. We cover the three phases of a typical session, how to read the information the system is showing you, what a normal muscle contraction looks and feels like, the adjustments you can make on the fly, how to recognise and respond to fatigue and spasticity, the warning signs that should prompt you to pause or stop, and what a carer or partner can usefully do while you cycle. By the end, you should feel confident that you know what "normal" and "not normal" look like, and that you have a clear plan for both.
The Shape of a Session
Most FES cycling sessions follow the same three-phase pattern: a warm-up, the active cycling itself, and a cool-down. The proportions vary between systems and between users, but the pattern is consistent for good reason. Muscles respond better when they are eased into work, and they recover better when they are eased out of it.
Many clients will perform FES cycling from a wheelchair, which can initially present some issues. Wheelchairs come in many different shapes and sizes. Many have fixed footplates that can prevent the wheelchair from getting too close to a bike. Some tend to be tippy, and others tend to be stable. In some cases, it's been necessary to place a small cushion behind the user's back, effectively moving them forward a little in the wheelchair so that cycling can commence. We need a pedal action that isn't blocked by the wheelchair's position. We don't want the legs to be pulled into full extension, nor do we want any part of the user's legs to rub against the wheelchair's framework. Check from behind that the user is positioned squarely in front of the bike, not at an angle to the left or right.
These all seem like basic things, but they can be irritating at first. You can be comforted by the fact that once you achieve satisfactory positioning, it's easy to replicate it in subsequent sessions.
Warm-up
The warm-up is typically 'passive' to begin with. This means the bike motor moves your legs through a gentle pedalling motion, usually at a slower speed than you will cycle at later. This does two useful things. It increases blood flow to the legs, priming the muscles for contraction, and stretches the joints through their available range, reducing the chance that a sudden strong contraction will meet resistance from a stiff knee or ankle.
As cycling begins, ensure that no part of the user's legs rubs against the wheelchair's metal frame nd that nothing obstructs the free movement of the pedals.
If you are someone whose legs tend to be spastic at the start of a session, a warm-up of five to ten minutes of passive cycling often reduces that spasticity noticeably before stimulation begins. Some systems can also apply a low level of stimulation during the warm-up to further help settle spasm patterns. Your clinician will have set this up if it is useful for you.
Active cycling
This is the main phase and the reason you are on the bike. The stimulator begins delivering pulses to each muscle group in time with the pedal position, and your legs begin contributing power to the pedalling motion. The method for increasing stimulation intensity will vary depending on the stimulator model.
On most systems, you will see a visible transition: the target speed climbs, the stimulation indicator shows pulses are being delivered, and if your muscles are responding, the bike motor quietly backs off because your legs are now doing some of the work.
Twenty to forty minutes of active cycling is typical for an established user. When you first start, you may manage only a few minutes before your muscles are spent, and that is entirely expected. Volume and consistency matter more than duration in any one session.
Cool-down
The cool-down mirrors the warm-up. Stimulation tails off and the motor returns to passively moving your legs for a few minutes at a gentle pace. This gives the cardiovascular system time to settle, clears the legs of waste products from hard work, and leaves the muscles in a relaxed state rather than a tense one. Skipping the cool-down is tempting when you are tired, but it is generally recommended.
Reading the Screen
Every FES cycling system shows you some live information while you cycle. The details differ between systems, but the core indicators are broadly the same. Understanding what each one is telling you is the difference between being a passenger and being in control of your session.
Parameter readouts
Frequency (Hz), pulse width (microseconds), and current (mA) are usually displayed for each muscle channel. You do not need to stare at these, but knowing roughly what they should be for you means you will spot it quickly if something is set wrongly. Your clinician will have written typical starting values into your programme.
What a Normal Contraction Looks and Feels Like
If you have sensation in your legs, an FES contraction feels like a strong tightening of the muscle, sometimes with a mild buzzing or tingling at the skin under the electrodes. The sensation is not usually painful, though it can feel unusual at first. It should feel firm, rhythmic, and in sync with the pedal movement. Electrode size and wear can influence how the stimulation feels.
If you do not have sensation, you are looking rather than feeling. A normal contraction looks like a clear, visible firming of the muscle belly under the skin, timed to the pedal stroke. The muscle should plump and relax rhythmically as the pedal comes round. The leg moves smoothly with the pedal rather than jerking against it.
What should not be happening: a contraction that recruits muscles you did not intend to stimulate (for example, the inner thigh twitching when you are driving the quadriceps), a prolonged contraction that does not relax between pedal strokes, or a leg that is visibly fighting the direction of the pedal. Any of these suggests that an electrode has shifted, a cable is in the wrong channel, or the settings need adjusting.
Making Adjustments During a Session
One of the advantages of modern FES cycling systems is that you can adjust the system's settings in real time while you are using it. You do not have to stop and start over.
Frequency
Frequency is the number of pulses per second being delivered. Higher frequencies produce stronger contractions, but the muscle will tire faster. Lower frequencies produce less force, but the muscle keeps working for longer. Most programmes start around 30 to 35 Hz as a sensible compromise. If a muscle is fading faster than you would like, reducing the frequency by 5 or 10 Hz often buys you more session time.
Current
Current (measured in milliamps) is the intensity (height) of each pulse. Increasing current recruits more muscle fibres and produces a stronger contraction. For complete spinal cord injuries, current values typically sit between 40 and 90 mA. If your legs are under-contributing and the settings look low for you, nudging the current up a small amount at a time is the usual first move. Most systems will have a maximum current per channel of between 100 and 130 mA. In most cases, you will not need to approach maximum current levels.
Pulse width
Pulse width is the duration of each pulse, measured in microseconds. Some systems have an adaptive mode that automatically adjusts pulse width to keep you at the target speed, increasing it as your muscles tire. The RehaMove 2 system worked in this way. If your system is doing this automatically, you will see the pulse width value climb as the session progresses. That is normal.
Pause and revive
When your muscles are clearly fatiguing (speed dropping, active contractions disappearing, stimulation still on), pausing stimulation for one or two minutes while the bike continues to move your legs passively allows the muscles to recover. When you re-engage, you will often get another productive block of cycling out of them. This is more effective than simply pushing the settings higher, which just fatigues the muscles faster.
Recognising and Responding to Fatigue
Muscles after a spinal cord injury fatigue differently from uninjured muscles. They tend to be dominated by fast-twitch fibres, which produce force quickly but also fatigue quickly. Electrical stimulation also recruits those fast-twitch fibres first, which is the reverse of what your nervous system would normally do. The practical consequence is that FES-driven muscles fatigue faster than you might expect, especially in the early weeks of training.
The signs to look for are:
- Your actual speed drops to the passive speed controlled by the bike
- The active-pedalling icon (if present) disappears even though stimulation is still being delivered.
- In systems with an adaptive mode, the pulse width climbs to keep the legs going.
- If you have sensation, a feeling of "emptiness" in the muscle, or a change in the quality of the contraction.
The right response is almost always to pause rather than to push. Over weeks and months of training the muscles adapt, shift towards more fatigue-resistant fibre types, and sustain longer sessions. The way you get there is by working the muscles productively and letting them recover, not by overworking them in a single session.
Spasticity During a Session
If you live with spasticity, an FES cycling session can interact with it in several ways. Mild spasticity often settles during the session itself because the rhythmic movement, repeated contractions, and fatigue all tend to reduce spasm. Many users report that their legs feel noticeably looser for hours after a session ends.
Occasionally, though, a spasm pattern will worsen during a session rather than improve. The usual triggers are a boot or strap pressing against an uncomfortable spot, a bladder that needs emptying, a position that pulls on the hips, or simply cold legs at the start of cycling. If a strong spasm pattern appears, pause the stimulation, let the bike continue passive cycling for a minute or two, and check the obvious causes. Most cycling bikes have a built-in spasticity response, as we described above, that briefly reverses pedal direction when they detect resistance; this is a safety feature, and you should let it do its job rather than trying to override it.
What you should not do is try to power through a spasm by increasing the stimulation. That usually makes things worse.
Warning Signs That Should Stop a Session
Most sessions are uneventful. A handful of situations, though, call for you to pause or stop and investigate. Learning to recognise them is worth more than any particular parameter setting.
Autonomic dysreflexia
If your injury is at T6 or above, autonomic dysreflexia is a risk you should be aware of at all times, not only during FES. It is triggered by a noxious stimulus below the level of injury (a full bladder, a bowel issue, a tight strap, an electrode causing pain you cannot feel) and produces a sudden, dangerous rise in blood pressure. The symptoms include a pounding headache, sweating above the level of injury, flushing, goosebumps, blurred vision, and a feeling that something is badly wrong. If any of these appear during a session, stop immediately, sit upright, loosen straps, and look for the cause. Seek medical help if symptoms do not settle quickly. This is not a reason to avoid FES cycling; it is a reason to know the signs.
A drop in blood pressure
Less dramatic but more common is orthostatic hypotension, a drop in blood pressure that can cause lightheadedness, dizziness, or a grey feeling. This is more likely at the start of a session if you have recently transferred, or at the end if stimulation stops abruptly. A proper warm-up and cool-down reduce the risk, and so does staying hydrated before your session.
New or changed pain
If a part of you that has sensation starts to hurt during a session, pause and investigate. Persistent skin pain under an electrode may mean the electrode has lost contact or is concentrating current unevenly. Joint pain may mean a strap is pulling the leg out of alignment. None of this is normal, and none of it should be pushed through.
A change in how the legs look
Pale skin, unusual mottling, a leg that has swollen during the session, or any obvious change from how the legs looked 10 minutes ago are reasons to stop and check. These are uncommon but worth catching early.
Skin, Temperature, and Positioning
Mid-session skin checks
It is worth a brief look at the skin under and around the electrodes during longer sessions. You are looking for redness that is spreading rather than settled, any sign of blistering, and any sign that an electrode has peeled up at an edge. On people with pale skin, a uniform pink under the electrode is normal and fades within an hour or two of the session; anything more pronounced is worth investigating. On darker skin, the visual change is subtler, so running a fingertip over the electrode edges to check for raised or weeping skin is useful.
Temperature
The legs warm up during FES cycling. That is the point. What you want to avoid is either of two extremes: legs that sweat freely onto the electrodes (which degrades the adhesive and reduces signal quality) or legs that stay cold throughout the session (which usually means circulation has not been prompted enough to respond). A warm room, a light covering during the warm-up if your room is cool, and a fan for longer sessions all help.
Upper-body positioning
Your upper body is not cycling, but it is working to keep you stable on the bike. Check periodically that you are not slumping sideways, that your arms are supported, and that your pelvis is symmetrical on the seat. Twenty minutes in a lopsided position will leave you sore in places that have nothing to do with the cycling itself.
Breathing
It sounds obvious, but breathe. A surprising number of people hold their breath during strong contractions, especially early on. Steady, relaxed breathing in time with the cycling motion is part of what makes a session feel sustainable.
The Carer or Partner Role
Many users cycle with a carer, partner, or family member present, especially in the early weeks. Their job is not to drive the session; it is to be a second pair of eyes. Useful things for them to do include:
- Fixing the feet and legs in position, getting overall positioning right, fixing electrodes and making electrode connections
- Watching the screen and flagging when the speed starts to drop.
- Watching the legs for any change in colour, position, or spasm pattern.
- Checking that straps and electrodes have not shifted during transfers or during the first few minutes of cycling.
- Helping with a mid-session skin check if reaching is difficult.
- Noting how you look in general: alert, comfortable, working, or strained.
If you are the carer reading this, the most valuable thing you can offer is calm attention. You do not need to know every stimulation parameter. You need to know what your person looks like on a good day so you can quickly notice when something is different.
Winding Down and What to Expect Afterwards
After the cool-down, stimulation is off, the bike has stopped, and you are ready to transfer. Take a moment before you move. A short pause lets the cardiovascular system settle, allows any mild lightheadedness to pass, and gives you a chance to check how your legs feel.
What is normal in the hours after a session:
- Warm legs that feel pleasantly tired.
- Looser muscles than before you cycled, especially if you live with spasticity.
- Mild skin pinkness under the electrode sites, fading within an hour or two.
What is not normal and should be followed up:
- Skin that is still visibly red, blistered, or sore the next day under an electrode.
- Muscle pain that is sharp rather than diffuse, or that persists beyond two or three days.
- Any joint that feels unstable or painful to move after a session.
- A new pattern of spasticity that persists for more than a day.