Defining Dynamic Wheeled Mobility

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.