ATP Series

Defining Dynamic Wheeled Mobility

PDG Mobility Elevation wheelchair

PDG Mobility’s Elevation wheelchair

Steve Mitchell is a clinician at the Cleveland VA Medical Center. Among his focuses are veterans with spinal cord injuries, and Mitchell himself is an ultralightweight wheelchair user.

Jaimie Borisoff, Ph.D., product manager of high-performance wheelchairs at PDG Mobility, also uses an ultralight wheelchair. In addition to designing for PDG, Borisoff is the Canada Research Chair in Rehabilitation Engineering Design at the British Columbia Institute of Technology.

Borisoff designed, and Mitchell has used, the new PDG Elevation, an ultralightweight manual wheelchair capable of changing configurations as its user’s environment or tasks demand.

Borisoff notes the different forms of dynamic seating systems, from “when you basically have a backrest or a footrest with a spring on it, and it’s for clients with tone and spasticity as a means of absorbing energy and/or increasing range of motion,” to manual wheelchair seating with tilt and recline: “And in most cases, it’s for the less-independent client. Often, they’re not independent drivers and, for example, have significant pressure management goals. In manual, it’s been primarily more about health and medical goals.”

And then there is the PDG Elevation, which empowers clients to quickly and routinely change their seated configurations.
“I’m using the term on the fly — independent adjustment for my chair and my seating,” Borisoff says. “The motivation behind it is function — things you can’t do or have difficulty doing. An additional benefit is also probably better health outcomes.”

Mitchell calls this concept dynamic wheeled mobility, and says it “represents an entirely different way of thinking about what the ultralight’s configuration should do for its user. It combines the concept of dynamic reconfiguration with the use of recently introduced add-on components to give users the ability to quickly change the base configuration of their chair for better usability in multiple environments and activities.”

The difference between dynamic wheeled mobility and dynamic seating, Mitchell adds, is “While both address problems caused by a static configuration, the similarities end there. Dynamic seating involves using designs and components which manage forces between the user and the seating system. It is a way to mitigate the effects of increased tone and excessive movement. Jaimie and I had independently come to the realization that the ability to dynamically reconfigure key aspects of an ultralight’s seating had a huge effect on the overall usability of the ultralight for the full-time active user. This is distinctly different from what I understand about dynamic seating.”

On-the-Fly Adjustments: Born of Necessity

The impetus for Elevation, Borisoff says, was a combination of factors: “A long-term buildup of things I was having difficulty doing, plus realization of a couple of things.”

Those revelations came from Borisoff’s observations about the many ways he’d used his wheelchairs in the past and in different environments, from the basketball court to the laboratory.

“I have very poor trunk control as a T3 para,” he says. “So how did I play basketball? I played in massive squeeze positions, 6" to 8". Your center of gravity is lower; you’re much more maneuverable. But you’re not going to see that in a day chair very often.

“I had a standing wheelchair that I used when I worked in research, basically to work at countertops, to be able to reach countertops, which is a more functional position in labs. But I found that I wasn’t standing in it at all. I was in a semi-standing position, but I was very stable and comfortable, I could still grab my wheels. I was in a functional position for working at a countertop.”

Mitchell, in contrast, remained capable of functional ambulation after his injury, but — as a clinician in a wheelchair seating clinic — he also had access to ultralight chairs. At his supervisor’s invitation, Mitchell began using them more frequently as time went on. “I began noticing as I was getting older that it was getting more and more difficult to stand for prolonged periods of time and cover distances, just the wear and tear that my body had taken,” he says. As he personally dialed in a borrowed wheelchair to be efficient around the hospital, Mitchell says he became fascinated by “the effect configuration had on efficiency.”

Unable to take the VA hospital’s wheelchair off the grounds, Mitchell eventually obtained his own wheelchair, “which has a very short wheelbase. It’s dialed in for very efficient propulsion on level surfaces, but I hit one of the expansion strips in the garage [at work], and I didn’t realize that these little casters that make it so easy to go on level surfaces are quite a liability when you’re outside.”

The result: “I did an endo my first time taking my chair to work, so I began realizing that even though I thought I knew how to configure a chair for work experience, when I began using it in the real world, that was a totally different animal altogether.”

Changing the Configuration to Fit the Task

Borisoff noticed that he rarely used his standing wheelchair to stand all the way up. “What if you could dial [a standing chair’s position] back to a semi-standing position?” he says. “You could use it all the time because it is lighter, less bulky and less heavy. A standing chair has too much structure for optimal wheeling. But could we keep the chair in the footprint of an ultralight?”

Mitchell noted that he sometimes felt uncomfortable on minivan wheelchair ramps “and I wondered why that was. Some of them are about 10°, and I just felt my chair was too tippy and I was having to lean forward too much.”

They had both identified multiple situations in which a static ultralight chair configuration was less than optimally efficient.

“Jaimie and I live on opposite sides of the continent and didn’t actually meet until we presented [a seminar at a conference] for the first time,” Mitchell says. “What we have in common is that we are both ultralight users with spinal cord injuries working in fields related to rehabilitation technology. We’ve learned through our own experience that one static configuration will never be optimal for every context in which we need to use our chairs. Unlike most end users, we have hands-on experience with ultralights that provide dynamic reconfiguration. Most of Jaimie’s experience is with the Elevation. Most of mine came as a result of using a sliding seat on a modified early-production Icon A1.”

As Mitchell refined his understanding of dynamic wheeled mobility, he streamlined his thinking into two “rules.”

“One is the law of mutually exclusive configurations,” he says. “There is an inverse relationship between the optimal configuration for level propulsion and the optimal configuration to do just about everything else. In an ultralight configured according to the wheelchair clinical practice guidelines, the user will tend to sit lower and further back in the chair relative to the wheels. The problem is that the user’s function tends to be best when they are situated higher and toward the front of the chair.

“I call the second rule the conservation of contextual angles. It holds that changing key angles of the ultralight, its user or the environment will require changes to angles elsewhere to offset that change. It sounds complicated, but it’s really about equilibrium. Someone sitting in a chair with a low rear seat height for efficient propulsion will probably be lower than a person who is sitting in an average dining room chair. Their hands will probably be near shoulder level whenever they wash dishes or cook at the stove. If they have to lean forward, additional shoulder flexion will be needed just to keep the hands at the same level. Keeping the hand below the shoulder is almost impossible. The ability to increase the rear seat height and adjust the back angle forward can make a significant difference.”

The conservation of contextual angles rule, Mitchell says, “explained for me why I was uncomfortable going up some ramps in my clients’ minivans. I have a seat angle of 14°, a back angle of 95°, and very little of my weight over the front casters. One day it dawned on me that if I am on a 10° ramp, my effective seat angle becomes 24°. My back angle is now 105° and provides no support. My chair also becomes much tippier. Because I have a static configuration, I am unable to restore my seat and back angles or change my position relative to the pushrims. My only option is to lean forward as much as I can to keep from flipping back as I push. Leaning forward results in very extreme wrist, elbow and shoulder angles.”

Changing Configurations in the Real World

Both Mitchell and Borisoff had come to the same conclusion: At different points in a user’s day, different seating and wheelchair configurations become ideal. Therefore, no single wheelchair configuration can always be optimal, assuming an active user engaging in many tasks each day in different locations.

“I live in Vancouver where it rains a lot, and it’s hilly,” Borisoff says as an example. “I’m wheeling when it’s wet, and when you’re going down a slope, you slide and grip, slide and grip because it’s slippery, and I’m hoping I don’t lose my grip and pitch into traffic.

“I thought, Hang on: Bring it down into maximum dump, open up the backrest, and you’re super stable. Now I’m very tippy on level ground so I need to be aware, but it’s great for going down slopes. Going uphill, it’s the opposite: Crank it way forward, and you’re super uncomfortable on level ground, but you’re going uphill. So it’s comfortable for that, you are less tippy, and you have a backrest to push against.”

One of the Elevation wheelchair’s most critical functions, Borisoff says, gets less attention “but is actually used more, and that’s de-elevation: getting into a more aggressive dump or squeeze.” Being able to adjust rear seat-to-floor angles relative to front seat-to-floor measurements can help with seated stability in many situations, including navigating slopes. “You throw it into fairly serious recline with maximum squeeze,” he says, “and you can go down slopes without having to be in a wheelie.”

A second major Elevation function is, as its name suggests, the ability to elevate the wheelchair’s seat. The result, though, is unlike what you’re used to seeing in power chairs, in which the seat rises along with the footplate, thus preserving the angle of the user’s legs. Nor is it the entirely upright, perpendicular positioning you typically see in a standing wheelchair or standing frame.

Instead, the Elevation’s seat elevation function is between the two, an intermediate position reminiscent of what you see in anterior tilt. Borisoff says the chair offers about 10" of seat elevation while retaining seated stability for its user, who sits in a sort of designed “pocket” while elevated.

“You can reach a shelf in your kitchen, a higher shelf at the grocery store, you can wheel up to a bar,” he says, adding that while elevated, the user can still reach the wheels to maneuver and propel. Elevation also offers an adjustable backrest: Open up the angle to adjust weight distribution and dial in the “tippiness” that’s great for going down hills. Close up the angle to get more backrest support while wheeling up-slope. In between, users can adjust back angle for comfort or to tackle a task at hand.

“It was easy to add in backrest adjustability,” Borisoff says. “What’s interesting about the backrest is the functional possibilities were not as obvious to me. It’s by far the most underutilized and underappreciated function.”

Borisoff further talks about seating situations other than wheeling. “Remember, we only spend about 10 percent of our time in a wheelchair actually wheeling — hat tip to [Stephen] Sprigle and [Sharon] Sonenblum. The rest of the time, we are simply sitting at a desk, doing the dishes, or any other daily activity. So adjustable positioning for different tasks can have a major impact on wheelchair seating, not only in propulsion. And just the ability to fidget or make small seating changes can improve comfort throughout the entire day, and probably pain and fatigue.”

Usable Dynamic Configurability

Seat elevation, an adjustable backrest and on-the-fly configurability weren’t the only features on Borisoff’s list of goals. He also had to incorporate all that added functionality without sacrificing the signature features of ultralight chairs: low overall chair weight and easy portability.

“That’s the secret sauce in this: I’m surprised I don’t get noticed more often,” he says, referring to the Elevation’s extra functional features. “That’s a design goal, too: [Elevation] is not any bigger; it doesn’t look any different unless you look underneath it. It has the same width and height of an ultralight chair.”

That’s especially critical to the ultralight user demographic. As an engineer, Borisoff is designing for an aesthetically savvy audience attuned to consumer trends. Their expectations for their personal wheelchairs is usually very different than the expectations of staffers buying manual tilt-in-space chairs to be used by their patients in long-term care and similar institutions.

“I refer to it as the ultralight form factor,” Borisoff says. “The [ultralight] user is more sophisticated, I think.”

The usability of a dynamic wheeled mobility system also comes down to time and convenience.

“In the first prototype [of the adjustable back control], it wasn’t a lever, it was a twist knob,” Borisoff recalls. “Have you ever adjusted the seat in an old Volkswagen? It’s the same thing, a twist knob, and it was a pain to adjust. You can imagine I never used it. It would take 15 seconds instead of one or two seconds with a [current Elevation] lever. It sounds ridiculous that the [time difference] would stop someone from using it, but it would. An adjustment that takes a long time to do is more akin to a better ATP nuts-and-bolts setup adjustment than to an on-the-fly adjustment that would be used instantly anytime during the day.

“That really speaks to the usability. There’s no point in making an ultralight wheelchair with on-the-fly adjustments that isn’t quick and easy to use. It’s just going to be abandoned.”

Mitchell includes add-on components in his interpretation of dynamic wheeled mobility, defining those components as “something that can be added to an optimally configured chair. The casters are usually the limiting factor in being able to use the chair outdoors, so the Free Wheel [wheelchair attachment] came out. You only use it when you need it, and when you take it off, your chair is no different than before you installed it.”

Other add-ons, by that definition, would include certain power-assist systems, such as Max Mobility’s SmartDrive, which Mitchell notes can be easily added to an ultralight chair and activated, but does not require a chair configuration change to use.

As for the future viability and need for dynamic wheeled mobility, Mitchell points out, “Legs and walking is a way to get your brain and your hands someplace to do something functional. Most functional activities are hard to do at a seated level, especially if you’re in a dialed-in chair where your rear seat-to-floor height is in the 16" to 17" range. Shoulders do wear out over time, and there’s ways that the wheelchair can be serving a different role, but we have to be able to have these adjustable angles to do that.”

“I envision my giving a talk at RESNA or ISS [International Seating Symposium] in the near future titled something like On-the-Fly Dynamic Seating for Ages 2 to 102,” Borisoff says. “There should be on-the-fly seating adjustability for almost all wheelchair users. That doesn’t always mean the adjustments are going to be made independently [by the user]. Say a parent has a 2-year-old and elevates him to the dinner table or to join in a family conversation. Imagine what that means for the quality of life for the parent and the kid both.”

“Unless one uses a chair that provides dynamic reconfiguration, they are unlikely to know what it can do,” Mitchell says. “It is my hope that clinicians and researchers come to a realization that relatively small dynamic adjustments can help preserve upper-limb function with only a negligible effect on weight. Until there is sufficient demand, we will find that the ultralight will continue to fall short in our ability to meaningfully implement the clinical practice guidelines in the very activities where they need to be implemented the most.

This article originally appeared in the November 2016 issue of Mobility Management.

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