Technology in the Spotlight

The Ergonomics of Ultralights

How to Make the Most of Every Ride -- for Life

• By Laurie Watanabe
• Aug 01, 2014

The frames of ultralightweight manual chairs are a much talked-about subject in the complex rehab technology world (see Mobility Management’s May 2014 issue) because of the impact they can have on the overall efficiency of mobility.

But if those wheelchair frames are mobility canvases, then other critical aft ermarket components are the paint. After all, how successful can a rigid or folding, aluminum, titanium or carbon fiber frame be if the seating and performance components aren’t a similarly good fit?

We quizzed manufacturers about how the components they make could ideally help to create an efficient, safe and comfortable ride for wheelchair users — and what’s important to keep in mind every step of the way.

Step 1: The Frame

We asked wheelchair manufacturers their top performance goals when designing ultralight chairs. Were they aiming to achieve durability with their products? Ease of propulsion? A comfortable ride all day long?

“It’s really a combination of all three, plus more,” says Christy Clover, associate product manager for adult manual, Sunrise Medical. “We are constantly challenging ourselves to create a product that, when spec’d for an individual’s unique needs, provides an outstanding ride experience throughout the lifetime of the product. There is always a lot of hype about what type of material is used for the frame — we’ve talked extensively about titanium vs. aluminum. To us, materials are important, but the overall design for long-term performance of the chair is key.”

Doug Garven, engineer & designer at TiLite, says, “All of these criteria factor into a new design, along with aesthetics. And once we’ve got a design that drives toward these goals, we add another critical ingredient: a tailored, individualized fit, what we call TiFit. We do not believe in a ‘one-size-fits-all’ approach. To really meet these performance goals, the chair must be fit to the person.”

Jeff Adams, president/CEO of Icon Wheelchairs, says his company is “very focused on making sure that the chair is exactly right the day it’s delivered and over its lifetime of use. Our main goal is to create a ‘situationally correct’ vehicle that can adapt to changing situations, which can mean having slightly different goals. Sometimes, the goal could be optimizing the chair for comfort; other times it could mean configuring it into the most efficient geometry — and the goal could change over time.

“For a brand-new user, the goal might be to build a comfortable, safe chair that is very conservatively configured — for that same person, the goal may change in a matter of days, or over longer periods of time as they go through the rehab process, and they develop and improve their chair skills.”

Linda Zettergren-Sopko, Invacare Corp.’s business manager for active & medium active wheelchairs, says the manufacturer focuses on “Performance frame. In trying to create an efficient product, the performance frame is designed to endure the aggressive rigors of everyday use while still maintaining an unparalleled roll. Critical to the design are the welded caster head tubes, which eliminate an adjustment in a highimpact area and preserve performance for the long haul.

“We combine high-quality design, durability and rollability in our product. We harmonize two conflicting forces: The first, moderately complex seating, which promotes effortless pushing and shoulder, elbow and wrist health. And second, the performance-minded consumer who expects unsurpassed performance every day. In short, our ultralight chairs are designed to always be in alignment, giving it the most efficient roll.”

Step 2: The Seating

A consumer can only capitalize on all the wheelchair frame has to offer if he/she is properly positioned for propulsion and function. How can backrest and cushion selection impact the overall performance and efficiency of an ultralightweight chair?

“The seating system can affect the performance and efficiency of an ultralightweight chair in many ways,” says Susan Cwiertnia, PT, MS, sales & education specialist at VARILITE. “There are multiple factors to consider and match up with the consumer’s individual needs.

“An obvious factor is the weight of the seating system. Why go to all of the trouble to obtain an ultralight wheelchair and put on a heavy cushion or back support with bulky hardware? The cushion should be lightweight, provide the appropriate level of skin protection to match the consumer’s needs, but should also provide a stable base of support for good trunk/sitting balance. Proximal stability equals distal mobility, which means the consumer will be more effective with upper extremities for propelling. The height of the back support is crucial because it needs to be high enough for trunk stability, but if it is too high it may interfere with upper-extremity range of motion during propulsion.”

Chris McFarland, ATP, education & mobility specialist for Comfort Company, says, “In order to optimize efficiency with wheelchair propulsion, the shoulder of the user should be in vertical alignment with (or slightly anterior of) the wheel axle. In order to configure this position in a wheelchair, an adjustable rear axle plate is required to allow the location of the rear wheel to be moved for each user’s needs.

“The key to optimal wheelchair propulsion is proper pelvic positioning (which should be in a neutral or slightly anterior position) and proper trunk support. This will provide proximal stability and allow the user to maximize independence with distal control (i.e., wheelchair propulsion and endurance).

“Seat cushions should be evaluated with each user’s needs to ensure that the cushion is providing proper pelvic positioning and proper pressure relief. Some seat cushions provide a contour in order to ensure proper pelvic positioning, some seat cushions provide pressure relief only, and some seat cushions provide a combination of both positioning and pressure relief qualities. Once the proper seat cushion is chosen, further adjustments may need to be made to the wheelchair: e.g., if a thicker seat cushion is required for proper pressure relief, the adjustable rear axle plate must again be adjusted for optimal handrim positioning.”

Cwiertnia adds, “The individualized fit of the adjustable ultralightweight wheelchair combined with the seating system should provide positioning not only for efficient propulsion, but also as much postural balance as possible. The balanced neutral posture can eliminate areas of high pressure created by an asymmetrical pelvis to assist with skin protection.”

Step 3: Performance Components

Positioning components and wheelchair frames may get the majority of attention in many seating & mobility discussions, but aftermarket components can also have a big impact on an ultralightweight wheelchair’s overall performance.

Handrims, for instance, are the energy interface between the wheelchair user and the wheelchair, but their significance to performance can often be overlooked.

“The performance goals of our ergonomic handrims, such as the Natural-Fit and the Surge, are to provide better pushing efficiency (strong push, less effort), eliminate pushing on the tire, and to provide greater control when braking,” says David Boninger, who handles marketing for Out-Front as well as TiLite. “All of these performance goals are achieved as a result of the larger, ergonomic gripping surface.”

In addition to efficiency, handrim selection can also impact the wheelchair user’s health, since the typical ultralight consumer makes contact with the handrims all day long…and ultimately, for decades over his or her lifetime.

“From a clinical standpoint, the most important goal is to ease the pain in the hands and wrists that is so common among manual chair users,” Boninger says. “The consumer that would be a good fit is any active chair user with good hand function: The good hand function is what allows the user to take of advantage of the ergonomic grip.

“The prevalence of upper limb pain and injury among manual chair users is very high. Some research puts the prevalence at over 70 percent of longtime chair users experiencing hand and/or wrist pain, such as that associated with carpal tunnel syndrome. The development of our handrims was specifically intended to reduce this prevalence of pain and injury by providing a more ergonomic option. When pain is prevalent, oftentimes without us even noticing it, other systems break down, too — and this could include posture as well.”

Wheels can also make an enormous difference in an ultralight’s performance, says Ryan Webb, director of sales/marketing for Spinergy.

“Today’s wheelchairs have advanced to become highly customized performance mobility devices,” he notes. “If the wheels don’t follow suit, then many of the benefits the wheelchair is meant to deliver won’t be realized. The goal of any wheelchair wheel should be to contribute to the efficiency of the propulsion, the rollability of the wheelchair, performance and comfort on all rolling surfaces, ease of transportation, durability and the list goes on.”

Webb says wheels in this particular market must do double duty.

“Wheelchair wheels have a harder job than wheels in any other industry,” he notes. “Think about it: Do we have to remove our car wheels and manually lift them five times a day? [Wheelchair wheels] must be lightweight, durable, stylish, designed to perform in all conditions.”

As with every complex rehab technology product, different consumers may have different priorities when choosing wheels.

“Improved performance should lead to better mobility,” Boninger says. “For some, better performance means a stiffer (less wheel flex), more efficient ride. For others, it’s all about the weight. And for still others, it more about the look. In terms of important factors in selecting wheels, those factors are typically strength, weight, lateral stiffness, cost, durability and ease of maintenance. What the correct ratio of those factors is depends on the user and their intended use. Last but not least, don’t forget styling. There’s not a single more influential component that can dramatically change the look and feel of a chair.”

It’s a testament to how far component engineering has come, Webb adds, that consumers and their seating & mobility teams now have so many performance component choices.

“The concept of ergonomics in a wheel or handrim design isn’t new,” he says. “However, it’s only been recently that significant design advancements have been made, exposing a whole new product category.

“I don’t feel it’s a niche market because every person using a wheelchair can benefit from ergonomic handrims! They’re more comfortable and are designed to prevent repetitive-use complications. It’s a matter of selecting the right design. Ask these questions: How is the person’s grip strength? Do they need a push surface with tack? Where do they need that tack — where the thumb rests or the top or side of the handrim? — and where do they need a smooth braking surface? What handrim shape/size best suits their hands? Answering these questions should lead to the best product, as it’s in these areas most designs differ.”

Webb adds, “Choosing the best wheels includes a different set of questions. As it pertains to ergonomics, wheel weight and rollability are most important. You can pick the best handrim for the client, but if the wheels are heavy or not designed with propulsion efficiency in mind, then unnecessary stress is the result.”

Step 4: Embrace the Possibilities

Of course, the first step to being able to create the best possible overall ultralight mobility system is knowing what seating, positioning and performance components are available to enhance the ultralightweight frame.

“The most important advice,” Garven says, “is to learn about the various options that are available so that the most appropriate selections can be made for each individual. TiLite offers a wide selection of different components that allows the user to choose exactly how they’d like their chair to look and perform. There is no right or wrong answer, as each customer has their own unique needs and applications — that’s why learning and self-educating are so important.”

“We always welcome creativity as it comes to each individual’s personalization of their product,” Clover says. “Our advice for consumers and their support teams would be to talk to peers and others about the obstacles they encounter on a daily basis and see if there is an accessory solution to help meet their needs. Reviewing a typical day with their care team can help bring to light some ideas and solutions.” It’s also important to be familiar with compatibility issues between the ultralight frame and aft ermarket components.

“Our ultralight products have the ability to address any seating or positioning need by adding any of our Matrx seating products onto the product platform,” Zettergren-Sopko says. “By incorporating transferfriendly features like quick-release axles, fold-down/lock back release and movable rigidizer bars, the rider can create a harmonious environment to help in ease of independence throughout the day.”

Another possibility: If you find an aft ermarket component that you want to use, but the ultralight frame won’t accommodate it, try explaining your situation to the ultralight manufacturer.

“We designed the Icon A1 to be compatible with as many aftermarket performance parts as possible,” Adams says, “and have been implementing changes as needed to make sure we’re compatible as possible.”

One example: Adams says Icon redesigned its footrest at the suggestions of clinicians and consumers who wanted better compatibility with the FreeWheel all-terrain attachment.

“Most aft ermarket parts will work with the Icon,” he adds. “If there’s something that anyone wants to use that isn’t compatible, please let us know, and we’ll put our thinking caps on and figure out a way to make it work.”

Webb confirms that there’s now a new world of ultralightweight performance possibilities thanks to technology advances, adding that today’s consumers “demand more for their money and are less willing to accept ‘what comes on the chair.’ It’s about products finally meeting the consumers’ demand for value and quality of life.”

This article originally appeared in the August 2014 issue of Mobility Management.