Midline Matters

While much about complex rehab seating and
positioning remains a mystery to those outside
the industry, popular fitness movements such
as CrossFit have made concepts of midline or
core strength and stability part of mainstream
conversation.

Take this excerpt from an Invictus Fitness post
called “What Is Core to Extremity?” by Bryce Smith:
“The core serves as a muscular corset that works as
a unit to provide stability both with and without
movement. All motions are generated from the core
and translated to the extremities. Core to extremity
means that the bridge that connects your upper
body to your lower body is tight and secure with no
loose ends and no broken beams. The midline is the
bridge that allows efficient and safe force transfer.”

For complex rehab clients, core stability is crucial
for function, such as the ability to sit in a position
that enables them to propel a manual wheelchair.
For power wheelchair users, core stability can make
it possible to reach and effectively use a joystick or
other type of driving control.

And for some power chair users, moving the
driving control front and center — to midline,
around the belly button — can make a huge difference
in function.

The Big Deal About Midline

Generally speaking, we have greater strength close
to our bodies than farther away. Imagine lifting a
gallon jug of water with one hand and extending
your arm so the jug is at arm’s length from your
body. Then imagine lifting that same jug, but
keeping your arm and the jug close to your body,
right around your midsection. Which position is
easier to maintain and is less fatiguing?

The loss of distal strength — that is, strength
farther away from the body — before the loss of
proximal (closer to the core of the body) strength
is common in some types of muscular dystrophy,
for example. But Michael Flowers, CEO/President of Active Controls, noted that this tendency can also present in
wheelchair users with other diagnoses.

“That rule really applies to all of the neurological disabilities,”
Flowers said. “It’s not really restricted to any particular one.”

Active Controls is best known for its centrally located power
wheelchair driving controls — controls positioned not on the
end of an armrest, which is the standard joystick location, but
closer to the power chair user’s core or midline.

“It was serendipitous,” Flowers said of finding that midline
location. “We had developed the JoyBar handlebar control” — a
power chair control that looks like a scooter tiller — “and the
only way to put a handlebar control on a power wheelchair is to
put it at midline, just like a scooter handlebar is always in the
center of the front of the scooter.”

After developing a modular system for that handlebar control,
Flowers recalls saying to a colleague, “This is just a connection.
We can put any type of control up here, including a joystick.”
That colleague responded, “If we can do a joystick, we can do
alternative driving controls.”

Flowers added that there’s a very practical reason that midline-mounted
controls can be easier for some power chair users to
operate. As Active Controls was designing its products, Flowers
noted, “I said, ‘If we do a joystick, we can do supports on each side
of the joystick to support the lower arm and relieve the stress and the
strain on the forearm and the heel of the hand.’ That would make it
so much easier to drive a power wheelchair. That’s how it all evolved.

“When we did that and developed the gel pads for [the
supports], we found that [midline controls are] not just for
people who can’t drive from the armrests. By supporting the
lower arm and the heel of the hand, you are using less muscles.
We confirmed that with the clinical study we did at MossRehab
Hospital [available on the www.ActiveControls.com Web site]. The
doctor who did the study [Alberto Esquenazi, M.D., MossRehab]
used muscle sensors to see which muscles were firing when you
drive from an armrest, and then he compared it to driving at
midline with lower-arm supports. And he confirmed that the
muscles that fire are basically in the shoulder and the neck — so
that’s your trapezoids. And it confirmed that you have less muscle
usage when you drive at midline with a lower-arm support. That
equals less fatigue and longer [power chair] usage during the day.”

Variations on the Midline Location

So if operating a joystick or other power chair driving control from
a midline location can require less effort and cause less fatigue, why
not just move all power chair driving controls front and center?

Because, as is seemingly always the case with complex rehab technology clients, what works for one person or even most
people isn’t the best answer for everyone.

As Education Coordinator for Adaptive Switch Laboratories
(ASL), Byron Guisbert is well versed not just in alternative
driving controls, but in making them work optimally for each
power chair user.

“Everyone is different,” Guisbert said. “Somewhere, sometime,
the ‘standard’ joystick position just happened to be at the end of an
armrest in almost exactly the same position on every manufacturer’s
[power chair]. I agree that there are individuals who could benefit
from having it placed elsewhere, but that could be inches left or right.

“For me, where the joystick is positioned is dependent on
what joystick, how much stability someone needs for their upper
extremities, how their hand needs to be positioned, where their
visual field is capable. What function are they using to move the
joystick — shoulder, arm, hand, fingers, etc.?”

Guisbert pointed out that mounting power chair controls in a
midline location requires those controls to swing away to allow
for transferring in and out of the chair. Some swing-away mounts
“swing away when you don’t want them to swing away,” he said.
And those mounts need to be able to return those power controls
to the exact same spot every time. It’s not just a matter of a power
chair user being finicky: It’s a matter of having learned how to
use those controls exactly where they were. Having controls in a
different location, even one just slightly different, could make it
difficult or impossible for the power chair user to function.

“The one thing they don’t like is change,” Guisbert said of
complex rehab power chair users.

Finding Each User’s Functional Sweet Spot

Guisbert noted that power chair consumers with complex seating
needs develop unique ways to use their power chair controls.

“The standard method became mounting [controls] on
an armrest, but they were standard for spinal cord injuries,”
Guisbert said of how joysticks originally came to be located.
“And if they had shoulder movement, that was awesome, because
they laid their hand on the armrest and they drove.

“But for me, it’s always a question of who am I working with? Am
I working with someone who’s using the shoulder, the entire chest
to use the joystick? Some people are even rotating their trunk. You
might find somebody using a hand-over-hand [method], where
they’re using both hands to utilize a joystick and actually rocking the
joystick itself. Are they rocking it by using the weight of their hands?”

Flowers agreed: Every power chair user is different.

“It extends beyond just the operation of the chair, and that’s
what to me has always been intriguing about driving in a position that is most comfortable for you,” he said. “Every one of us has a
different sweet spot.” Active Controls’ Ergo ReJoy, Flowers noted,
gives seating teams greater ability to find that “sweet spot.”

“We always try to get as close to the core, or the belly button,
as possible to start,” Flowers said. “But what we’ve found is
that you can actually move [the controls] all around and firmly
position it where anybody’s hand naturally falls in front of their
body. Usually, it’s going to be within 2″ or 3″ of the core, and
most people are going to be right in the center. However, there
are some people that have shorter arms, and reaching over to
the center isn’t a natural feel for them. And you really want
the person’s elbow supported by the armrest at the same time,
because that also relieves the muscle usage in the trapezoid.

“If you balance the position where they drive from, you
balance the position of the rest of the body.”

Guisbert’s additional concerns, beyond how functional a
power chair user would be with midline controls, were the environmental
accessibility restrictions that can come from having
controls mounted front and center.

“For anything you do that’s awesome, there’s something that
you’re hindering,” he pointed out, about midline mounting and
perhaps about complex rehab technology choices in general. “For
me, midline joysticks almost eliminated pulling [up] to a table.
That’s almost priceless to me — for everybody to be in the same
place, whether I’m in a chair or out of a chair. If I’m eating at the
table, I want [them to be able to.]. If I’m working at a workspace,
they should be able to acquire that.”

Guisbert acknowledged that if a power chair user was highly
functional with midline-mounted controls, he wouldn’t rule that
positioning out. But he cautioned against generic questions such
as “What mounting controls position should you use for cerebral
palsy clients?”, because having a diagnosis does not make
everyone with that diagnosis exactly the same.

“These are all individuals,” he said. “It all depends on the
family, the person, if they’re using their shoulder. If they put the
joystick midline and are using their right arm, all of a sudden
they might be pushing to the left a little more aggressively than
they would be going forward.”

So as with everything else in complex rehab, midline
mounting can be helpful to some power chair users, but each
client is a case unto themselves.

And Guisbert is fine with that.

“To me, joystick users — they don’t need us,” he said of power
chair consumers who can efficiently use standard controls. “I’m
glad they have us, but for the people that need us the most, we’ve
got to figure out where they do their best function.”