Training Denervated Muscle With the RISE Stimulator and Its Patient Switcher: From Twitch to Standing

The patient switcher for the RISE Stimulator is a small white box on a long white cable. One rocker switch turns the current on and off. A second sends it to the left leg, the right leg, or both. A curved steel bar on the back hooks over a parallel bar, so the box sits under the hand of the person standing.

The patient switcher is the simplest accessory we supply for the RISE, and you could argue it's the one that takes longest to earn. Someone training denervated thigh muscles will usually spend the best part of a year, often longer, before it has any job to do. Training denervated muscle requires commitment and if it's a long time since injury, it takes consistent effort to be able to produce strong enough contractions to make use of the patient switcher.

A few months into training, once the thighs have started to fill out again, the conversation tends to turn to what all the effort is leading to. Sometimes the question is more direct: will I stand? This article is my answer, from the first twitch to the first stand, and what it takes to do that safely in a hospital gym or at home.

We supply the RISE Stimulator and its patient switcher in the UK, so I have a commercial interest in this subject. And I'm not a physiotherapist. I'm a bioengineer, and I've spent most of my working life with stimulators, so I can tell you what the device does and why the training is sequenced the way it is. Whether and when a particular person wants to stand and use the patient switcher is a decision for them and their own clinical team.

Why a denervated thigh needs a different kind of stimulation

Most electrical stimulation doesn't stimulate muscle at all. It stimulates the nerve, and the nerve does the rest. That is why an "ordinary" NMES or FES unit gets by with pulses lasting a fraction of a millisecond.

When the lower motor neurons are lost, there is no nerve left to excite. That is the situation after a complete injury to the conus medullaris or cauda equina, which commonly leaves the muscles of both legs denervated, and after some peripheral nerve injuries, such as damage to the femoral nerve, which can leave one thigh denervated. The muscle fibres then have to be excited directly, and muscle membrane responds far more slowly than nerve. The pulses have to last tens or hundreds of milliseconds, the current has to be much higher, and the electrodes have to cover as much of the muscle as possible, because there is no motor point to aim at. I have covered the biology in Normal vs Denervated Muscle, and why a standard unit produces nothing in Why your NMES product probably doesn't work with denervated muscle.

The RISE Stimulator is made in Austria by Dr. Schuhfried Medizintechnik. It has two independent output channels and delivers biphasic pulses of up to 400 milliseconds at currents of up to 250 milliamps. Its manual reserves currents of 150 milliamps and above for muscles with flaccid paralysis, and rules out adhesive electrodes at these higher currents. Wet sponge electrodes, or rubber electrodes with a salt-free gel, are used instead, held in place with straps. One note if you read the manual alongside this article: Schuhfried quotes the pulse duration as the total of both halves of the biphasic pulse, so a 120 millisecond pulse is 60 milliseconds each way.

Where the training plan comes from

The plan in the RISE manual has a long Viennese pedigree. Schuhfried has built electrotherapy equipment since 1947, developing current types with Professor Hans Jantsch at the Vienna General Hospital. The modern plan comes from Helmut Kern and his colleagues in Vienna. As early as 1999 they reported people with complete injuries at the junction of the thoracic and lumbar spine standing up from sitting in parallel bars, after one to two years of training that began with twitches, moved to tetanic contractions and then added ankle weights (Kern 1999).

The largest test of this sequence was the European RISE programme, from which the stimulator we use evolved. It followed 25 people with complete lower motor neuron lesions through two years of home-based stimulation of the thigh muscles, and 20 completed it (Kern 2010, two-year report). Quadriceps cross-sectional area rose by 35 per cent, mean muscle fibre diameter by 75 per cent, and the knee extension torque produced by stimulation rose from 0.8 to 10.3 newton metres. Biopsies from the same group showed that the machinery a muscle fibre needs to contract, which long-term denervation dismantles, can be rebuilt by stimulation (Kern 2004). And the gain in force was enough for a quarter of those who completed the programme to perform FES-assisted stand-up exercises.

That last figure matters for this article, and I will come back to it. The manufacturer says its outlined training table is based on these studies.

KEY POINT: The RISE training plan condenses a research protocol tested over two years in people with complete lower motor neuron injuries. It rebuilt muscle tissue in most who completed it. Standing came at the end, and only for a minority.

Twitches come first, and there is a reason

A thigh that has been denervated for months or years cannot produce a sustained contraction on demand. Its fibres have shrunk, and the structures that link an electrical signal on the fibre's surface to the release of calcium inside it have broken down. A tetanic contraction attempt asks for something the muscle has lost the means to deliver. So training starts with single twitches: one long pulse, one contraction, repeated about twice a second. We refer to these as "twitch" contractions because that's the effect you see as stimulation is applied.

The manual divides the twitch period into two phases:

• Phase 1, roughly the first four months: pulses of 120 to 150 milliseconds with a 400 millisecond gap between them, delivered in eight second surges with two seconds' rest. Three or four sets of three minutes, with one or two minutes rest between sets. As muscle tissue normalises, longer sets can be used without fatigue.

• Phase 2, roughly months two to six: the same pattern with the pulses shortened to 70 to 100 milliseconds, and four or five three minute sets.

Both phases run five days a week, and the factory presets (PS1 and PS5) hold the 120 millisecond programme allowing easy selection of the program by a user.

Intensity is turned up until the muscle twitches strongly; if nothing clear appears at full intensity, the pulse is lengthened to 150 or even 200 milliseconds. If the contractions fade during a session, the manual says not to chase them with more current but to rest and resume, the principle behind Denervated Muscle Stimulation: Why Optimal Intensity Beats Maximum Intensity. Treating too intensively can cause sore muscles and raised creatine kinase, a marker of muscle damage which is obviously detrimental to progress.

Progress shows up by being able to use shorter impulse durations: as the muscle recovers its excitability it responds more readily to briefer pulses, so the pulse duration is stepped down while the gap between them stays the same. The manual's signal to leave the twitch stage is achieving a good contraction at around 70 milliseconds impulse duration, or a measured knee extension torque of about 3 newton metres. The RISE's built-in pulse test can be used to find the shortest pulse that still produces a clear contraction, a number that should fall as training succeeds; I have described it in Evaluating denervated muscle with the RISE stimulator.

The manual calls all of its timings reference values. Progress depends heavily on how long ago the injury happened and how consistently the person trains.

KEY POINT: Twitch training is not a warm-up. It rebuilds the muscle's ability to respond at all, and its progress is measured by how short a pulse the muscle will answer. Twitch training is essential to normalise the muscle tissue structure. Moving on is decided by the muscle's response, not the calendar.

Tetanic contractions and the first leg raise

Once the muscle answers a 70 millisecond pulse cleanly, it can start to work to generate force. Tetanic stimulation uses much shorter pulses, around 40 milliseconds, with only 10 milliseconds between them, so they arrive about twenty times a second. Each twitch begins before the last has relaxed, and the twitches fuse into one sustained contraction that can do mechanical work.

Phase 3 starts at roughly months four to twelve, uses 40 to 50 millisecond pulses in four second surges with two seconds' rest. The presets PS2 and PS6 hold this pattern (it was called DEN40 on earlier Schuhfried units). The work is now counted in repetitions rather than minutes: four to six sets of 20 to 40 contractions, with one or two minutes between sets.

With the person sitting upright, a four second tetanic surge through electrodes on the front of the thigh straightens the knee. The lower leg rises, holds and lowers again. It is the first time the stimulation produces movement rather than a flicker, and it can be the first visible proof that the twitch months were worth it.

From here the user manual separates two programmes by their intention:

• Strength endurance: seated knee extensions without added weight, 20 to 30 repetitions, later up to 40, in four to six sets with one or two minutes' rest. Once or twice a day.

• Strength: seated knee extensions with ankle weights of 0.5 to 4 kilograms, 8 to 10 repetitions, in four to six sets. Once or twice a week.

Its suggested week has four strength endurance days, two rest days and one weighted session, with room for some twitch sessions. Ankle weights also give you a measure you can take at home without a dynamometer: the weight you can lift for a set number of repetitions, written down week by week. In other arenas, we would refer to this as progressive resistance training.

Leg extension exercise with denervated muscle

Where sensation is preserved and rectangular pulses are uncomfortable, or where neighbouring muscles with a working nerve supply contract when they shouldn't, the manual suggests triangular pulses. Triangular pulses are the traditional way that denervated muscle was stimulated. A slowly rising pulse lets a nerve adapt and stay quiet, while any denervated muscle in the area still responds. There is a trade-off though: the gentler the slope of the triangle, the less effective the training.

KEY POINT: Tetanic training is where the rebuilt muscle starts to do work. The seated leg raise, first unloaded and then against ankle weights, is the training ground for everything that follows, and a progress measure you can record at home.

Why standing means the surge has to go

Phase 4, roughly months eight to twenty-four, keeps the 40 millisecond pulse and the 10 millisecond gap and drops the surge altogether. The manual says this phase must be used for standing up or walking in the parallel bars, because both need a constant contraction, and its table lists standing, walking in place and walking. The research behind it is more modest about walking, and I will come to that.

The manual grades quadriceps progress from 0, no visible contraction, to 4, standing by bracing temporarily on a standing table or parallel bars. The Vienna group graded their participants the same way, and after one year, 4 of 20 had reached the top class (Kern 2010, one-year report).

Why lose the surge? In every earlier phase, the stimulator decides when the muscle contracts: a four second surge, two seconds of rest, repeated for as long as the programme runs. That's fine on a plinth, lifting your lower leg. It's useless, and dangerous, when your knees are holding you up. Standing on a timer would mean your knees giving way every few seconds.

So control has to pass from the timer to the person standing. With the surge removed, the RISE delivers a continuous tetanic train whenever a channel is live, and somebody has to decide, moment by moment, which channel that is. The Vienna researchers describe their standing, stepping in place and walking exercises as using "continuous stimulation (controlled by an external switch)" (Kern and Carraro 2020). They don't say who held the switch, or whether it could choose one leg over the other. The patient switcher puts that control in the hand of the person standing.

None of the factory presets is set up for this; every one has a surge. A programmable slot has to be configured without one, which is a job for whoever sets up your device, not something to improvise.

How the patient switcher works

The switcher plugs into its own socket on the right side of the RISE case. Connect it before starting a session, because the channels can only be switched if the session began with it connected.

It has two controls:

• The on/off switch. At "O", nothing reaches either channel, whatever the intensity dials say. At "I", current flows to whichever channel the second switch selects.

• The channel switch. In the middle position, both channels are live. Pushed one way, channel 1 alone; the other way, channel 2 alone.

With channel 1 on the left quadriceps and channel 2 on the right, the person standing can stimulate both thighs, either thigh alone, or neither, without letting go of the bar.

Several manual rules matter in practice:

• Start a session with the switcher at "O" and both channels are greyed out on the screen. The intensities found in seated training can still be dialled in, but nothing is delivered until the switch goes to "I".

• If the switcher is unplugged during a session, both channels switch off.

• The pulse test can't be used while the switcher is connected.

• Before first use, check the switcher from the settings menu (System, then Patient switcher), which shows the channel each position selects without delivering current. If it doesn't match the manual's table, don't use the switcher until the fault is put right.

Two of those rules cut both ways. The on/off switch is the quickest way to stop the stimulation, which is what you want in the hand of the person standing. But off means off on both legs at once, and so does a pulled cable. If both quadriceps are holding the knees straight and the current stops, the knees will bend. This obviously follows from how the switcher works. So the cable should be routed where it can't snag, the box should hang where an elbow won't knock it, and nobody should stand on stimulated quadriceps without a chair close behind them and a trained person beside them.

The manual doesn't describe a sequence for standing or stepping, so what follows is the logic of the controls rather than a protocol, and your physiotherapist will adapt it to you. Seated at the bars, the switcher at "O", the intensities set, the channel switch in the middle. Hands on the bars, weight forward, and the switch goes to "I" as you push up: both knees straighten. To step in place, weight is shifted onto the arms and one leg, and the channel switch moves to that leg alone. The other quadriceps relaxes, its knee can bend, and that foot can be unloaded. Back to the middle and the knee straightens again, then the same on the other side. Sitting down is the reverse, lowered with the arms onto a chair or wheelchair that is already in place.

One more rule applies to anyone helping. At high currents, the manual says the person supervising must not touch the electrodes while current is flowing, so a helper steadying someone in the bars should hold the pelvis or trunk, not the thighs.

KEY POINT: The patient switcher hands the timing of the contraction to the person standing. That is what makes standing and stepping possible on denervated thighs, and why the setup around it matters: one switch, or one pulled cable, stops both legs at once.

A hospital gym or your own living room

The manual doesn't say where standing should happen, only who may operate the device: clinicians, and people they have trained for home use. A majority of our home users at the moment don't have parallel bars and don't necessarily have a routine visit from a physiotherapist. For this reason, the vast majority don't have or use the patient switcher device but they should at least know the option exists.

Before anyone stands. Bone comes first. After a spinal cord injury, bone is lost rapidly below the level of injury, and an international position statement estimates that more than half of people with motor complete injuries will have an osteoporotic fracture, most often just above or just below the knee (Morse 2019). A small study found knee bone density lower still where the muscles were denervated (Alazzam 2023). The only bone finding from the Vienna programme is improved strength in the kneecap, from imaging models (Gargiulo 2011); nothing shows that the training protects the thigh bone or shin. Current consensus advice is that bone density, joint range and leg alignment should all be considered before any loading therapy, that no bone density value absolutely rules out weight bearing, and that fracture risk should be discussed with the person and their agreement recorded (Craven 2023).

So before standing on legs that have not borne weight for a long time, ask your medical team whether your bone density should be checked, and how your blood pressure copes with being upright. The manual also excludes stimulation of unstable areas after fractures. And the electrodes sit on skin that usually cannot feel them, so it needs checking before and after every session.

In a hospital or clinic. A therapy gym has what a first stand needs: fixed parallel bars, a chair behind, a physiotherapist and often a second pair of hands, sometimes a standing table too. It is the sensible place to find out whether standing is realistic, set the intensities and learn the switcher sequence.

At home. Denervated muscle training is long-term home treatment, and the Vienna results came from home-based programmes. Standing at home is possible once the technique is established, but the room has to be set up for it. If it isn't set up with parallel bars and a support person is not available, then we would recommend progressing to use leg raises whilst seated. These are the requirements if standing is an option.

• Freestanding parallel bars that adjust to the person's height, on a firm, level floor, with room behind for the wheelchair.

• The RISE stimulator available on a flat, dry, stable surface beside the bars, not stacked on other equipment, with its power socket kept accessible. The manual rules out wet rooms.

• Leads long enough to reach both thighs without pulling taut when the person stands, and the switcher cable routed clear of feet and wheels.

• Mobile phones kept at least a metre from the device, no shortwave or microwave therapy equipment within three metres, and children and pets away from the controls.

• A trained carer present for every standing session.

Electrodes for standing. The thigh changes shape as the muscle contracts and the leg takes weight, so the straps must keep even pressure over the whole electrode. Sponges can dry out during a session, and as they dry the resistance to stimulation rises. If it rises far enough, the RISE cannot deliver the set current and shows an exclamation mark on that channel. On a plinth, that means a weaker leg raise. Standing, it means a weaker knee which won't be stable. Re-wet the sponges between sets.

Locking it down. The RISE has a home application mode, set up by the clinician or supplier with a six digit password. Only approved programmes can be selected, settings cannot be changed, and every session is logged in a record the user can view but not delete. So the standing programme need not appear on the device until your physiotherapist is satisfied you are ready.

KEY POINT: Standing on denervated legs should only be attempted when the person, the room and the equipment are ready. Bone health comes first, a trained person stands beside you every time, and home application mode lets your clinician decide when the standing programme appears.

What standing will and will not give you

At this point, you might be thinking that standing and walking sounds like a difficult activity that's going to take time to achieve, so is it worth it? Let's consider the evidence because standing is where claims for this kind of stimulation most easily outrun what has been shown.

A quarter of the people who completed the two-year Vienna programme performed FES-assisted stand-up exercises (Kern 2010, two-year report). That is a quarter of the 20 who finished, not the 25 who started, and it means standing up with support in parallel bars, not standing unaided. The group's own review is blunter: only younger and low-weight patients can expect to be able to stand up, and walking is for those who are young and light. In their cohort, it was the more compliant who became able to stand and step in place (Kern and Carraro 2014). No paper I have found says how many reached stepping in place. There is a case report of knee torque becoming sufficient to stand without support from the arms (Kern 2005), and it describes one person.

The 1999 report linked standing up from sitting in parallel bars with quadriceps torques of 16 to 38 newton metres (Kern 1999). The average in the larger RISE cohort after two years was 10.3. My reading, not the authors', is that the typical participant ended well short of the force associated with standing up, which fits the idea that standing was being reached by a minority. Quoting the 16 to 38 figure without the 10.3 overstates the case.

Research does not report walking in any everyday sense. Even rebuilt, a denervated muscle remains a denervated muscle: it still needs long pulses, it does not regain the excitability of muscle with a working nerve supply (Kern and Carraro 2014), and it is not under voluntary control. Standing on it is an exercise you do, with stimulation, inside a frame of support. It is not a way of getting about.

There is also no trial of the switcher itself. What I cannot tell you is that a study shows people who use one end up with better muscle, bone or skin than people who train seated, because no such study exists. What I can tell you is the mechanism: a surge-driven programme cannot hold a person upright, and the switcher turns continuous stimulation into something the person standing can control. More broadly, this whole approach rests on cohort studies, largely from one research group, not randomised trials. The tissue findings are consistent; the functional ones are smaller and apply to fewer people.

KEY POINT: Standing with the patient switcher is a training exercise for a minority, typically younger and lighter people who have worked through every earlier stage. It is not walking, and nobody should buy a RISE expecting it. The tissue benefits of training come whether or not you ever stand.

What I would suggest

If you are training with the RISE now, ask your physiotherapist to record where you are on the progress scale, and to repeat the pulse test at each review. The shortest pulse your muscle responds to, and the weight it can lift, will tell you more than the calendar.

If standing is a goal, raise it with your medical team before anyone attempts it, and ask specifically about bone density and blood pressure.

If you already have a switcher, run the check in the settings menu before first use, and practise the switch positions on that screen, where nothing is output, until they are automatic.

Where we come in is assessment. When someone we supply reaches the later stages of training, we can review the session log, repeat the pulse test, and look at whether the seated leg raise is strong enough to make standing worth attempting. If it is, we can supply the switcher as an optional accessory, set up a surge-free programme, approve it in home application mode, and go through the sequence seated with the person and their carer before anyone stands, ideally alongside their physiotherapist. We would follow up after about six weeks. If we think standing is not realistic yet, or at all, we say so; the seated programme still does its job.

Decisions about your treatment belong with you and your clinicians, and nothing we do replaces that relationship.

If you're training with the RISE and wondering what comes next, or you're a physiotherapist supervising someone who is, I'd be glad to talk it through.

Further reading

• Kern H, Hofer C, Strohhofer M, Mayr W, Richter W, Stöhr H. Standing up with denervated muscles in humans using functional electrical stimulation. Artificial Organs 1999;23(5):447 to 452. https://doi.org/10.1046/j.1525-1594.1999.06376.x

• Kern H, Boncompagni S, Rossini K, Mayr W, Fanò G, Zanin ME, et al. Long-term denervation in humans causes degeneration of both contractile and excitation-contraction coupling apparatus, which is reversible by functional electrical stimulation (FES): a role for myofiber regeneration? Journal of Neuropathology and Experimental Neurology 2004;63(9):919 to 931. https://doi.org/10.1093/jnen/63.9.919

• Kern H, Salmons S, Mayr W, Rossini K, Carraro U. Recovery of long-term denervated human muscles induced by electrical stimulation. Muscle and Nerve 2005;31(1):98 to 101. https://doi.org/10.1002/mus.20149

• Kern H, Carraro U, Adami N, Hofer C, Loefler S, Vogelauer M, et al. One year of home-based daily FES in complete lower motor neuron paraplegia: recovery of tetanic contractility drives the structural improvements of denervated muscle. Neurological Research 2010;32(1):5 to 12. https://doi.org/10.1179/174313209X385644

• Kern H, Carraro U, Adami N, Biral D, Hofer C, Forstner C, et al. Home-based functional electrical stimulation rescues permanently denervated muscles in paraplegic patients with complete lower motor neuron lesion. Neurorehabilitation and Neural Repair 2010;24(8):709 to 721. https://doi.org/10.1177/1545968310366129

• Gargiulo P, Reynisson PJ, Helgason B, Kern H, Mayr W, Ingvarsson P, et al. Muscle, tendons, and bone: structural changes during denervation and FES treatment. Neurological Research 2011;33(7):750 to 758. https://doi.org/10.1179/1743132811Y.0000000007

• Kern H, Carraro U. Home-based functional electrical stimulation for long-term denervated human muscle: history, basics, results and perspectives of the Vienna rehabilitation strategy. European Journal of Translational Myology 2014;24(1):3296. https://doi.org/10.4081/ejtm.2014.3296

• Kern H, Carraro U. Home-based functional electrical stimulation of human permanent denervated muscles: a narrative review on diagnostics, managements, results and byproducts revisited 2020. Diagnostics 2020;10(8):529. https://doi.org/10.3390/diagnostics10080529

• Morse LR, Biering-Soerensen F, Carbone LD, Cervinka T, Cirnigliaro CM, Johnston TE, et al. Bone mineral density testing in spinal cord injury: 2019 ISCD official position. Journal of Clinical Densitometry 2019;22(4):554 to 566. https://doi.org/10.1016/j.jocd.2019.07.012

• Alazzam AM, Goldsmith JA, Khalil RE, Khan MR, Gorgey AS. Denervation impacts muscle quality and knee bone mineral density after spinal cord injury. Spinal Cord 2023;61(4):276 to 284. https://doi.org/10.1038/s41393-023-00885-3

• Craven BC, Cirnigliaro CM, Carbone LD, Tsang P, Morse LR. The pathophysiology, identification and management of fracture risk, sublesional osteoporosis and fracture among adults with spinal cord injury. Journal of Personalized Medicine 2023;13(6):966. https://doi.org/10.3390/jpm13060966

• SCHUHFRIED GmbH. Stimulator RISE 5 E2x electrotherapy device: operating instructions, version E. Moedling: SCHUHFRIED GmbH; 2024. https://www.schuhfriedmed.com

Related articles on our site

• Normal vs Denervated Muscle: Why the Rules of Electrical Stimulation Change After Nerve Injury

• Why your NMES product probably doesn't work with denervated muscle

• Evaluating denervated muscle with the RISE stimulator

• Denervated Muscle Stimulation: Why Optimal Intensity Beats Maximum Intensity

• Creating an Assessment Report and Training Plan for the RISE Stimulator

• Cauda Equina Syndrome and Denervated Muscle: Your Options for Long-Term Health

• Electrical Stimulation and Muscle Quality: Why a Bigger Muscle Is Not the Whole Story

• Standing Up Again: How Responsive Electrical Stimulation Can Support Sit-to-Stand Practice

Articles on this site are researched and drafted with the help of AI tools, then checked, edited and approved by me. Every citation is verified against the original source before publication.