ATP Series

Stability at the Core

Why Stabilizing the Midsection Can Improve Mobility & Function

3 objects balancing


Given the highly individualized nature of complex rehab seating and mobility, there are few statements that can be applied across the board. But here’s one:

Core stability is a key factor that critically contributes to a wheelchair user’s functional abilities.

In fact, so much of a user’s general health and functioning is impacted by stability of the midsection — its strength, its balance, its durability. So what can be done to optimize core stability, and what can be done to improve it when it’s lacking?

Stability’s Impact on Daily Activities

How does core stability relate to a wheelchair user’s activities of daily living (ADLs)?

“This is a big question,” said Kathleen Simpson, MS, Bodypoint’s Director of M2M Sales. “An entire article can be devoted to answering it. With a focus on postural supports, I would answer as follows: If the wheelchair user does not have core stability, then the user’s function will be limited perhaps in key ways when performing ADLs. Proximal stability provides distal mobility and function, so during the seating evaluation performed by a trained professional, seating needs, function and limitations should be identified and solutions found to meet those needs. If the right chair, the right seat, and the right back have been provided and the wheelchair user still does not have core stability, then additional postural supports should be considered.”

“The core affects everything,” said Jean Sayre, MSOT, ATP, CEAC, VP of Research & Clinical Development for Quantum Rehab. “I think about everyday sitting and normal sitting behavior: If you don’t have a lot of core strength, sitting in your chair and reaching forward to grab a drink could make you fall over. You don’t have that function.”

Bart Van der Heyden, PT, Bodypoint’s Country Manager, noted that a lack of core stability can result in a long list of problems, including these:

  • Fall risk, and the user working too hard to keep his/her trunk positioned against the back of the wheelchair, or going into posterior pelvic tilt and sliding in the chair.
  • Shoulders moving forward, lack of head alignment, neck pain.
  • Collapsing chest and difficulty in holding the upper body in place.
  • Inability of the legs to stay together.
  • Stiffness in calves or ankles; feet fall off of footplates.
  • Fatiguing from the strain of reaching to the side to grasp the joystick.
  • Fatigue during activities that require greater range of motion, such as playing sports or traveling, even if the user generally does not have a stability problem.

“If a wheelchair user is sliding and slouching in the chair,” said Matthew Kosh, Bodypoint’s President and co-founder, “then simple activities such as reaching or propelling the wheelchair are more difficult and tiring. Posterior pelvic tilt results in a kyphotic posture, which reduces upper-body strength and requires more effort to balance the weight of the head — naturally, it is a more exhausting way to sit. A kyphotic posture further results in shallow breathing, lowering blood oxygenation and stamina. Lastly, if seated with a posterior pelvic tilt too long, there is an increased risk for sacral sores, which ultimately has the most damaging effect on sitting tolerance.”

Stability for Manual & Power Wheelchair Users

A lack of core stability for a manual wheelchair user can make the act of self-propelling much more labor intensive.

“One of things often overlooked by self propellers is how much their position slips while propelling the wheelchair,” Simpson said. “Most self-propellers don’t even realize this is happening.”

Athletes, she noted, are typically more aware of their body positioning: “Wheelchair athletes recognize the need to secure the pelvis, and in many sports strap themselves into the chairs. These athletes want to feel like part of the chair rather than just sitting on top so that they can better control their chair and perform their sport.

“When working with these athletes, Bodypoint asks them to try a belt in their active chairs to test whether their push strength is greater and more efficient. The universal response is that securing their thighs/pelvis absolutely increases push strength and efficiency, which in the long run will protect their shoulders and provide more longevity in pushing their chair. Non-athletes can benefit from the same principle.”

For power chair users, a lack of core stability can be even more dire.

“Obviously, all the solutions mentioned previously can apply to the power chair user,” Simpson said. “One thing that is often overlooked, however, is the position of the joystick control. Imagine you were trying to write a note, but had to do it off to the side rather than putting the paper centered in front of your body. Your penmanship might suffer. Yet the power chair user is expected to perform all the power functions of the chair with a joystick placed at the end of one arm of the chair.

“Many power chair users will sit better, with improved core strength and endurance, when a midline joystick is mounted on their chair. It is often more natural and easier for the power chair user to manage the power functions of the chair with the joystick mounted in front of their body rather than off to one side.”

Power chair users, Sayre said, can have a lot of trouble repositioning themselves once they get out of their optimal position.

As part of the research process that went into designing a new power chair, Sayre interviewed current power chair users. She recalled what a client who had multiple sclerosis told her.

“She said, ‘It’s so hard because I fatigue, and when I’m going outdoors, and I hit a bump, I’m not in midline. I’m pushed over. And it’s harder for me to get up and back into midline. If I had a smoother-riding wheelchair….’ That’s why we work so hard on putting suspensions in our chairs. When users get knocked out [of midline], it changes their whole function. It changes their strength. They can fatigue a lot easier.”

Core Stability Strategies

Creating or supporting core stability isn’t just a matter of building up a seating system. It’s designing a system that’s going to work with the client without getting in the way of the client’s goals and activities.

“We’re designing seating systems, the cushions and the backs, to work with the person, not against the person,” Sayre said. “I feel it’s like an exoskeleton of the body. The seating system needs to do what the body can’t do for that person.”

For a manual wheelchair user, adjusting seat-to-floor height so the rear height is lower than the front height can help with stability.

“We talk about putting dump in the chair because [users] have a poor core to begin with, so they collapse their trunk,” Sayre explained. “Some of those clients wear abdominal binders because it helps to maintain the core and helps them to propel that chair and not collapse. Some people will add dump and create more slope because now you’re closing that hip angle. If when you’re sitting you collapse your ribcage on your pelvis, you’re creating stability there. And you’re able to propel.”

Sayre believes in choosing a seat cushion and a backrest that will work together, as two parts of a unified system, rather than choosing those components separately.

“The seating system — the back and the cushion — need to function together,” she said. “You want to keep that pelvis nice and tight, so you’re going to build into that seating system a little bit more for that person to have functionality.

“People tend to think about the cushion all the time and forget about the back. But the back is just as important as the cushion. They really need to work together. That’s why it’s called a seating system.”

She explained that a seat cushion isn’t capable of performing all of the positioning functions that some clients need: “You can’t get everything out of the cushion. With the pelvis, you’re trying to prevent any kind of posterior sacral sitting and the posterior tilt of the pelvis, so you try to correct that with the design of the cushion. But you’re also looking for skin protection. You might build up the laterals a little bit on the sides and maybe the abductor to keep that person stable with the pelvis.

“But what you need to do also is have that back support. Even at that sacral level, that back system should be having contact. Where’s the scapula contacting, and do they need that scapular contact or not? Because if they have a better core, you may be able to open up that scapula so they have more function of the upper extremities. That even applies to power, because they need their upper extremities for the controller if they’re still using a hand controller.”

Components for Core Stability

Sayre said she tries to create as much stability as possible using a positioning cushion and a contoured back; for example, she likes trying a deep contoured back — one that wraps around the sides — before trying positioning components that add weight to the chair and can also potentially hinder transferring in and out of the chair.

But for some clients, the positioning offered by the seat cushion and the backrest aren’t enough support. That’s when adding a carefully considered set of positioning components can help.

“Core stability starts with accurate and carefully selected wheelchair seats and backs as the base of support,” Kosh said. “But since gravity alone is not enough to keep the person from shifting, a good belt applied in the right position can make a world of difference.

“Belts should be fitted according to the user’s individual needs, but a good starting point in most cases is worn across the thighs, with the belt pulling at about a 70° to 90° angle from the seat. This position is more comfortable for the wheelchair user than when mounted across the lower abdomen or hips at 45°. It is also more effective in helping to keep them engaged with the seating system to maintain core stability and benefit from the available support below the thighs and ITs [ischial tuberosities], as well as against the PSIS [posterior superior iliac spine] and lower back. By helping to maintain a favorable posture, sitting tolerance is increased, reducing the onset of normal daily fatigue.”

As the next step, Kosh said, “If the trunk is not stable after mounting the right belt in the right position, then anterior and lateral trunk supports should be considered. There are many harness styles to choose from with dynamic or static harnesses and chest supports to meet the user’s needs.”

And finally, he added, “Don’t forget the feet! Because of the weight of the legs, foot position has a huge influence on the position of the pelvis and, therefore, the trunk — if the feet are not stably supported at the proper height to evenly distribute pressure under the thighs and pelvis, the user will slip into a less functional position which is difficult to maintain.”

Creating All-Day Support

An eternal challenge when working with complex rehab clients is that they are always changing — as their conditions progress or as they naturally age, for sure, but also just as they tire during the day.

“A person in the morning can be totally different than what you see in the afternoon,” Sayre said. “Their core stability has probably been altered by what they’ve had to do throughout the day.”

Someone who doesn’t appear to need lateral support in the morning, Sayre explained, could need that support later in the day. The job of the engineers who design seating and mobility systems includes being able to offer core stability later in the day, but not saddling clients with unneeded equipment when they don’t need it, such as when they’re stronger in the mornings.

“Part of the challenges in designing and development is what can we do to give that person alternative solutions?” Sayre said. “Do they really need laterals, or can we use a different kind of contour for the backrest? Can we contour it around them a little bit more so we can remove the laterals? They may not need that support in the morning, but in the afternoon, they will.”

Sayre pointed out that while core stability is certainly needed for activities such as self propelling or using a joystick effectively, it’s also important to other bodily functions.

“We talk about dynamic activity, but let’s talk about static inactivity,” she said. “Breathing, digestion, bowel movements, the vascular system. If that person has a little more core stability, they’re able to take a deeper breath. They can open up their diaphragm. Hopefully, there’s less chance of them ending up with pneumonia. Look at feeding and core stability: eating and being able to get a drink. If you have that seating system and you open up that chest cavity and you extend the spine and tighten that pelvis and stabilize it, that will help those bodily functions.”

A crucial reason to provide core stability is that for better or worse, the body will find a way to stabilize itself… and not all of those ways are clinically efficacious.

“The body is extremely intelligent,” Sayre said. “It’s just instinctive. I feel like every person we work with, we can make them or break them. People are very complicated. That’s why we call it complex rehab.”

This article originally appeared in the May 2019 issue of Mobility Management.

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