Generations of scientists have disproved the notion of a perpetual motion machine — one that could run indefinitely without a sustaining source of energy — but it’s easy to guess where the idea for such a machine originated. Just look at a toddler.

While all humans innately want and need to move, young children have a special need and desire to do so. Among other reasons, being able to move through space on their own is critical to their physical, neurological, social and emotional development.

For kids who use seating & mobility equipment, however, the equation is more complex. Mobility-related conditions and clinical needs for positioning can seem at odds sometimes with the need to move for movement’s sake. Maybe that’s why dynamic seating is such a hot topic. But what does it really mean? How can it be achieved? And which kids are likely to benefit?

Defining Dynamic Seating

Generic definitions of the word “dynamic” generally involve two concepts: (1) motion and (2) ongoing changes to an existing condition — in this case, for instance, changes to a static position.

When it comes to seating & positioning, the experts interviewed for this story described “dynamic seating” as most often being used in one of two ways:

• As an overall concept of enabling a client to functionally move while within a seating system and/or to receive feedback about their movement while they’re in the seating system.
• To describe seating & positioning equipment that has some form of built-in ability to move when acted upon by the client, then return to its original position. The entire seating system may be able to move, or the “dynamic” function may be restricted to certain parts of the system, such as the wheelchair back. Also refers to equipment that provides motion-based feedback to the client as the client is in the system.

In both cases, the client’s movement sets the seating equipment in motion or results in a motion-based response from the seating equipment.

So what sorts of clients are liable to benefit from this ability to move or from this sort of movement-related feedback?

Dynamic vs. Static Seating

Anyone who sits for long periods of time — at a desk, in a car or on a plane — knows what happens when the human body is made to stay still.

ExoMotion’s Kathrin Brinks is an occupational therapist based in Germany.

“We all know that we feel very uncomfortable if we have to sit even for a short while in a very rigid position,” she says. “The back is aching, the neck becomes stiffer and stiffer, and the legs fall asleep. The longer we have to sit in the same position, the harder it becomes to sit upright. That is because our muscles need movement and sensual input for their blood circulation and for goal-oriented activity.”

For children with mobility issues, the results can be even worse.

“With all that knowledge, our regular solution for kids with too little ability for independent seating is still to station them in one rigid position,” Brinks says. “As a therapist, I have seen many seating solutions for special needs kids. And they usually have the same problem: They hold kids tight in one position without the possibility to move. Then their trunk muscles become ‘lazy’ or weaker. The muscles are not really needed, so they switch off, in standby. A child with a weak or an unstable trunk is becoming even more unstable the longer he sits in a rigid position.”

For children with other challenges — such as developmental delays — having to sit still can deprive them of much-needed vestibular input. The Vestibular Disorders Association (VEDA) notes that the human vestibularvestibular system relays information to the brain regarding the body’s movement and balance.

Stefanie Laurence, OT, education manager, Motion Specialties, notes that such children “are really thrusting and throwing themselves in the seating system not because of tone, but because of their vestibular needs, their sensory needs.” Equipping these kids with dynamic seating, Laurence says, “gives vestibular input. So they’re being held in their seating system, but they’re able to self-stimulate.”

Dynamic seating is perhaps most often mentioned in conjunction with kids who have high tone and are continually pushing against their wheelchair’s components, including the backrest, armrests and footrests. For these children, dynamic seating can mean a systemthat doesn’t “fight” them, but instead allows them to move and then returns them to a functional position.

Regardless of what kind of seating is needed, the pediatric experts interviewed emphasized the need to examine a child’s ongoing ability to function with and within the system.

Dave Hintzman, president of Bodypoint, says, “We’ve been so equipment intensive in the last few decades that we’re really missing an awful lot about what movements are required for a person. When you look at the literature, we’re not really seeing a lot out there on task performance in a wheelchair. What are the positions required for task performance as opposed to preventing orthopedic deformities or pressure sores, which have been kind of the things that we’ve really relied on?

“With that in mind, where I’d like the conversation to go is ‘What are we trying to do? Are we looking for some sort of seated performance? Do we know how well seated people do in their chairs? Do we have any information about this? Do we know anything about human potential?’”

A Look at Dynamic Seating Technology

Dynamic seating — when defined as allowing movement within a seating system — can be accomplished in a number of ways, including via tilt.

Dynamic seating can even be accomplished, Hintzman pointed out, by using traditional components in less than traditional ways. “What we wanted to do with our products is educate people about movement,” he says.

“So if they use a belt on a chair — like any of our hip belts — what we’re trying to educate them about is if they can move it in front of the trochanter as opposed to at 45 degrees, they’ve freed the person’s pelvis up to move in a range of motion that may be accessible to them, but that wouldn’t be accessible to them if it were at 45 degrees and locking the pelvis in place.

“So that’s not dynamic from an equipment standpoint, but it’s dynamic from a human potential standpoint. It allows movement, which is a really exciting way to begin to look at how we seat people.”

Ginny Paleg, PT, MPT, DScPT, mentioned “off-the-shelf” dynamic systems, including Snug Seat’s X:Panda, Rifton’s Activity Chair, Kids Up’s Kids Rock system (see MMBeat) and the ThevoTwist from ExoMotion. She also mentioned Prime Engineering’s KidWalk Gait Mobility System.

Laurence — who says, “I end up now looking at the issues from an equipment perspective” because she is not currently a treating therapist — described dynamic seating equipment in terms of the sorts of movement they encourage and allow.

The Kids Rock system, she notes, was designed to be used “as a wheelchair, and they’ve got their stroller as well. They really are designed for active movement or changes between seat and back angle and the possibility of knee movement as well — so, fullbody extension.”

In comparison, a system such as the X:Panda “has a fixed knee angle, but has the ability to go between seat and back — it changes between the seat and the back angle.”

Those sorts of systems, Laurence says, “and the Kids Rock in particular, are designed to be the primary mobility base with lots of postural support. So this is the kid we’re looking at that has excessive tone, really can move in and out of position, and we have the ability to block out (the movement). But the piece that is important is we’re looking at somebody who needs postural support.”

Some systems, such as the X:Panda, can be used on mobility bases as well as high-low bases, thereby increasing the systems’ flexibility.

“Go one step further,” Laurence says, “and what we end up having is the Rifton activity chair, where this is not designed to be a mobility piece of equipment. This is a piece of equipment that’s designed for use in the classroom, for use around the home, alternate seating. We’re not putting it on a wheelchair base. We’re really now saying we have the ability to get that anterior tilt, to bring somebody forward. We can get their feet on the floor, we can get their feet off the floor, we can put it on a high-low base. We can actually set this system up for someone truly to be active. Yes, we have the ability to do some positioning with it, but we’re not doing highly aggressive positioning, like we might with an X:Panda or a Kids Rock. What we are able to do, though, is (make it) much easier for a caregiver or a teacher to make changes to enable the child to function.”

Laurence also mentioned a DeGage dynamic back: “I see that Invacare is selling it on their Solara 3G, and it’s a piece that goes into an existing wheelchair with a polymer that harnesses the energy or is able to blow off and absorb the energy from somebody that is thrusting back and forth.”

Different manufacturer goals and equipment designs have also led to differences in construction and engineering — something Laurence calls “the piece I haven’t gotten my head around yet.” As an example, she says, “Do you use a gas cylinder or do you use a spring or do you use a polymer? Because each one of them functions differently because it’s an issue of how much force or how much effort does it take to initiate the movement? And then is the force constant, so there’s a counterforce back?

“Is it constant throughout the range, or does the force required to compress it increase as you go down? If you think about a spring, it’s easy to start compressing at the top, it’s harder the more you compress the spring. Whereas a hydraulic cylinder has a difference — they operate differently.”

Indications & Contraindications

With all these different equipment choices, when should clinicians and providers consider assessing a child for dynamic seating?

Speaking of systems designed to provide vestibular feedback, Brinks says, “We have seen many very hypotonic kids that benefit a lot from dynamic seating. They become more powerful in trunk stabilization, and that offers them better possibilities in using their upper extremities. And a very nice side effect is that the children feel very comfortable in the seating system. They have less pain and because of the open, breathable back, they are sweating less than in regular systems.”

For kids who need that vestibular input,
the seating system can help because it “offers sensory input and little movements that the child can feel in the upper body, while sitting as appropriately positioned as possible. The very base of concentration and learning is a good and secure body image. Otherwise, the child is not able to focus on a mental issue because he is busy searching for input for his body.”

Brinks says that even children in a comatose or vegetative state could possibly benefit: “We have seen some of them becoming calmer and breathing more deeply. But these kids, especially, need time to get acclimated in a new seat.”

Both Paleg and Laurence cited dynamic seating research done by the Italian group Fumagalli.

“They did one on dynamic seating and pressure distribution and dystonia: Quantitative comparison between rigid seat systems and dynamic seat systems using dynamic analysis,” Laurence says. “They were looking at the X:Panda specifically, I believe, and what they found was a reduction in the intensity of non-voluntary movement; (increased) tolerance for sitting; pain reduction; reduction of skin breakdown and breakdown of equipment. Those are what their conclusions were, and they were looking specifically at kids with CP.”

Paleg also referenced research by Dr. Michael Hahn on the Kids Rock system. Hahn presented his findings in 2007 at the International Seating Symposium in Orlando, Fla.

“The findings in Dr. Hahn’s study were nothing statistically significant; it was all trends,” Paleg says. Still, she says the study reported “a decrease in spasticity, an increase in range of motion, and actually improvement on the GMFCS (Gross Motor Function Classification System) for crawling and walking.”

When would dynamic seating not be indicated?

Paleg says, “If it’s a kid that’s stimming all the time and you feel (dynamic seating) would be a distraction and take away from function. (Or) if somebody has a spinal or a hip condition where repeated motion could inflame the joint or contribute to a breakdown of the joint. With someone who’s incredibly windswept and asymmetrical, all the devices only move in a symmetrical way, so if someone is actually de-symmetrical, I think that that could actually harm them.”

Another possible contraindication: Kids who have extremely severe tone or active movements (see sidebar).

Dynamic seating is “not likely,” Brinks says, “for the real hard pusher.” For those kids, the back provides too much potential movement, she explains.

But overall, for a range of mobility-related diagnoses and conditions — from cerebral palsy (including athetoid and spastic quadriplegia) to neuromuscular disorders to hypotonia to developmental disorders and disorders on the autism spectrum — an assessment for dynamic seating could be beneficial.

“I think there’s a very broad range of folks that have the human potential for movement,” Hintzman says when asked which seating & mobility clients might be good candidates for dynamic seating. “And probably more diagnoses than fewer.”

“It really gets back to goal-oriented seating,” Laurence says. “What are you trying to achieve? To say that one dynamic seating system didn’t work doesn’t mean the others won’t.”

Matching the Right Dynamic Seating Solution to the Client

As with all complex rehab technology, dynamic seating does require a thorough assessment to ensure the right equipment is being matched to meet a specific client’s needs.

“We usually get spasticity and tone when we take somebody through a quick movement,” Laurence says. “So we want to make sure, for example, that if we’re going to have something that allows somebody to move, we’re actually moving them in a modulated way — that it’s not a really fast reaction so we’re eliciting spasticity and tone. We want calm, gentle movement so that we’re controlling the dynamic movement of it, and we provide kids stability so they can grade their movement. If it’s free flowing, are we giving them guidance? Or are we just letting the
body move however it wants?”

A client’s goals are also important to consider when choosing a dynamic seating system.

“When we work with kids in particular — and I’ll say kids because most of these products have started out aimed at the kids market — when we put them in the classroom, we don’t want them in a resting position,” Laurence says. “We want them in an active, come-forward, do-stuff position. We’re really activating their reticular systems and not having them laying back in sort of this hit-me-with-it-or-I-might-fall-asleep-here position. I want them coming forward with their arms on the desk and engaging in what’s going on. As a therapist, that’s what you want to see. And we want to get them to the height of their peers, to the height of the work surface and everything else.

“So from that perspective, you can actually look at dynamic seating and say, ‘Is it just that I want to be able to change the seattoback angle and blow off extra overflow energy, or do I mean ‘dynamic seating’ that I can do more positioning and have different movements so the person can be dynamic, be active, do stuff — and I can take them back and have them rest?”

Because changing that seat-to-back angle can cause other changes as well, Laurence cautions, “We have to be very careful. If we want to give somebody the movement, we have to rethink about how we provide positioning. Traditionally, if you think that the seatbelt goes at that 45-degree angle to really lock the pelvis in, to be perfectly honest — for kids where we want them to move and have that ability to extend back and come forward, we have to let their pelvis move. We probably have to be looking at 60-degree belts so that the pelvis can rock back and forth because we want them to be dynamic, we want them to be able to move.

“No, we don’t want their butt moving from the chair, but I do want them to be able to move their trunk back and forth, not lock their pelvis in. Because trunk movement really should be coming from your pelvis, not your lumbar/thoracic spine. So one of my fears is, and where clinicians get stuck is, number one — they apply traditional seating principles to it: Lock everything in and then we’ll allow a little bit to move. But we’re not. We’re getting them stuck in a posterior position. And really, dynamic seating is not just posterior, it’s coming anterior as well.”

Laurence also recommends being sure kids using dynamic seating don’t get “stuck” once they go into extension.

“The other piece I start to look at with the systems: “Is there the ability to lock in the range that somebody can move? Because with some kids with CP — and again, these are gradations and differences between kids — at what point can the child move in and out of that extension? If we give them a backrest that moves, are we feeding into an extensor pattern?

“The feedback I’ve gotten from my colleagues is ‘It didn’t work. We put him in it, and he stayed stuck in extension.’ Well, the issue is, where is the sweet spot? You can extend a little bit, but if you go past the point of no return, you’re in a full pattern and can’t get out of it. And that’s where I see the biggest issue right now, when people say it doesn’t work. Because they’ve put a child in it who needs the seating to provide them the control so they don’t get into a full extension pattern. “So it works well for kids where they have some fl uctuations in their tone. It’s not good for the kid who’s going to be extending all the time and can’t get out of it.”

The Promise of Dynamic Seating

Thanks to a larger number of equipment choices and more research into its positive impact, dynamic seating has become a hot topic in complex rehab technology circles.

“It’s turned into kind of a catch-all phrase which relates to parts that move on the chair,” Hintzman says. He adds that he and his Bodypoint colleagues are “looking at how can positioning be stable, but not static?”

Laurence says, “My fear is that right now it’s sort of the flavor of the month, and everybody’s jumping on it and not really taking time to say, ‘What does dynamic seating really mean, and how do I best make it work for my client? Or is it appropriate for my client? There’s real differences in what dynamic seating really means.”

Part of the assessment process will be to determine what issues dynamic seating is being called upon to address.

For example, if therapists or providers are considering a system in which the back moves or the client moves through space, Laurence suggests, “You’re either trying to decrease tone because we’re allowing movement so you’re not getting this overflow pattern of tone that’s happening because somebody’s fighting the seating system, or we’re looking at it because the equipment is breaking. And that’s where I start to look and say, ‘Are you prescribing the dynamic seating because you’re looking at dynamic seating for the user so they can move and get range of motion and not fight their seating system? And when are we prescribing a product because we don’t want something broken? (Because we’re) tired of replacing backcanes that are breaking, tired of upholstery that bottoms out at the top, or the wear pattern is directly behind the shoulders because that’s where it’s taking the beating by the individual?

“Dynamic seating means a lot of different things,” Laurence says. “It’s movement between seat-to-back angle — or is it dynamic seating as in we can set the seating system up in different ways so the child themselves can be dynamic?”

It’s a dynamic question for a technology and a philosophy that are still evolving and being defined.

“In the past,” Hintzman says, “we didn’t assess children in terms of human potential as much as we assessed them for the equipment need. I think that’s why dynamic seating is so exciting to me, because it means so much more than what the equipment can do.”