Benefits of the Adjustability of the APEX Wheelchair

When you are looking for an ultralight rigid wheelchair, either for yourself or a client, the need for adjustability can be essential. As a rider uses their wheelchair, they may find that they need a different or even a second set of wheels. Being able to adjust rear-wheel spacing gives the rider the luxury of making these changes throughout the lifetime of their chair. Perhaps the rider wants to increase their seat slope to improve stability.  To change seat slope, you need vertical adjustability of the axle and, ideally, a quick and easy way to square the casters.  Having the ability to perform adjustments on the wheelchair can be crucial, whether the change is needed for improved mobility or due to the worsening of a condition - look no further than the APEX. The APEX's rigid frame is designed for intuitive and identical adjustments on both carbon and aluminum models.

What Makes Our Adjustments So Intuitive?

• Laser-etched markings in the carbon fiber and aluminum to ensure symmetry
• Built-in bubble level for quick and easy squaring of the casters
• Simple Allen key adjustments with torque settings inscribed on the wheelchair
• Easy access to low-profile clamps and hardware for COG adjustment
• Motion Composites tool kit – available on the order form, with every tool needed for adjusting the APEX
• Step-by-step instruction sheets

Let’s talk about how these adjustments are not only intuitive in design but also very much engineered with clinical needs in mind.  We will look at 5 key adjustments:

1. Center of gravity
2. Rear seat to floor height
3. Seat-to-back angle
4. Casters
5. Rear wheel spacing

Whether you are an end-user yourself, or a clinician/provider looking into the justification for the APEX, we hope to explain how this rigid chair stands out among others in its class.

Center of gravity (COG)

COG adjustment is referred to as the horizontal adjustment of the axle plate and camber tube (they’re connected in a rigid wheelchair design).

How much horizontal movement do you get with the APEX? Infinite adjustability, up to 6” of forward horizontal positioning of the rear wheels. This allows for a very aggressive or very stable placement of the rear wheels as needed. Riders who need a more forward rear wheel could include those wanting optimal maneuverability or those with more forward posture asymmetries such as kyphosis. A kyphotic posture moves more of the rider’s weight forward, requiring a more forward rear wheel to capture the center of mass over the drive wheel. Ideally, we want the center of the rear wheel axle to be at or in front of the rider’s shoulder, as shown below.

^{Ideal COG adjustment starting position, shown here by the vertical line at the front of the rider’s shoulder.}

This improves the overall efficiency of the system but also helps create a more biomechanically advantageous position of the shoulder for each push stroke, something that can occur 3,000-5,000 times a day!  Another very popular reason to choose such an adjustable rear axle with a rigid wheelchair is so that you can adjust it over time. Skill level, injuries, pregnancy, and diagnosis may all be reasons you need to adjust the horizontal center of gravity over the lifespan of a wheelchair. (Check out our lifetime warranty on our APEX Carbon) The one thing that the above reasons have in common, is the need to alter the stability of the wheelchair. As a rider improves their wheelchair skills, they may be able to tolerate a more aggressive center of gravity to improve their maneuverability.  On the flip side, a potential need to stabilize the system would be a temporary injury or even a decline in condition. Pregnancy is one of those unique scenarios that drastically alters the rider’s center of mass over a short period of time (short is relative, as pregnancy can be extremely taxing on those moms-to-be!) Being able to adjust the center of gravity backward and forward throughout pregnancy and post-partum can be extremely beneficial to overall energy conservation!

Clinical Consideration: Do you have a bariatric client who could also benefit from the performance of a rigid wheelchair? Check out our HELIO HD or our VELOCE HD wheelchairs! Heavy Duty without the Heavy.

Rear Seat to floor height

Once you start adjusting the rear wheels or center of gravity, you may need to adjust other features of the rigid wheelchair. Thankfully, the APEX gives you adjustability at every turn, so you can dial in the rider’s needs, no matter the reason. Let’s stay on the topic of the rear axle and discuss adjusting the rear seat to floor height. On the APEX, this is infinitely adjustable, and it is easy to specify an exact position for the rider. The seat slope adjustment can be utilized for all sorts of functional needs, such as trunk stability, pelvic positioning, comfort, or even environmental access. A rider may want to adjust this to get a feel for different slopes in their seat to find the sweet spot for their most functional and efficient day-to-day activities. An inch too high may be the difference in grabbing something off the ground or could cause too much instability of the trunk, making that reach for the coffee mug in the morning too difficult or even impossible. It is important to adjust adjustable wheelchairs to allow riders an opportunity for an even more successful, efficient lifestyle.

Seat-to-Back Angle

Specifically, when adjusting the rear seat to floor height, you are going to need to at least consider the seat-to-back angle. Adjusting the vertical position of the rear axle changes the seat-to-back angle. Even minor adjustments can create an uncomfortable or ill-fitting angle for the pelvis. Refer to the range of motion of the hips and pelvis, and consider trunk stability. Sometimes, a more “squeezed” (acute) angle of the seat-to-back cane creates stability for the rider, but not everyone can achieve that amount of hip flexion. Open seat-to-back angles are required for some who have temporary orthotics or even riders who are newer to their wheelchair. A more open angle may give them the stability and comfort they are searching for. The geriatric population can benefit from a more open-back angle as well. Whether you achieve a change in seat-to-back angle with the back canes themselves, with solid backrest hardware, or both, this is a crucial adjustment for all wheelchair riders.

_{Adjustable seat-to-back angle hardware: 80-101 degrees in 3-degree increments}

Casters

You know the book, “When You Give A Mouse A Cookie”? Well, that book represents the cause-and-effect action that custom ultralight rigid wheelchairs require when adjusting them. After you’ve made any adjustments to COG, rear seat to floor height, or any movement of the system’s center of mass, you need to re-square the casters. Squaring the casters is how you avoid caster flutter and maintain efficiency. The caster housings must be perpendicular (90 degrees) to the ground to work properly. Uniquely on the APEX and the VELOCE wheelchairs, we offer a built-in bubble level that allows this adjustment to be done quickly and precisely without the need for any squaring tools.

Rear Wheel Spacing

A smaller, but at times a pertinent adjustment, is rear wheel spacing. It is defined as it sounds: the space between the rear wheel and the wheelchair. A common reason for increasing rear wheel spacing is a change out of tires to a wider option, typically off-road or knobby tires. Wheelchair prescribers do not want to add additional width to the seat just to accommodate clothing or larger coats in the winter. Increasing wheel spacing can also be a solution for this in the colder months and can be adjusted back to a narrower position for the remainder of the year. 

Other adjustable features of the APEX:

• Depth adjustable back options
  • All our components are clamped on with our patented low-profile precision clamps. That means you can effectively change frame length or seat depth as needed if the initial measurements are not adequate for the client. It also allows seat depth growth for pediatric clients and has compatibility with WC-19.
• Tension adjustable back upholstery
• Double-pull seat straps
  • Adjust tension or adjust the width of straps (we offer 1” and 2” straps to allow sliding of the component clamps along the seat frame)
• Footrest height
  • The amount of taper should be considered when factoring in the amount of adjustability needed. This feature allows you to dial in proper lower extremity positioning. 
• Height of back canes (must be selected on the order form)
• Armrest height

Of course, other adjustments that can be made to create the ultimate dialed-in configuration for any rider, but those adjustments may require ordering different parts.  These adjustments were not discussed in this blog but certainly can be altered when needed by any client.

What we promise with the APEX is a fully adjustable, fully modular, rigid wheelchair that can be adjusted for comfort and precision. The intuitive design and engineering quality make this the future for any rider’s mobility needs.  

References

1. Rehabilitation Engineering & Assistive Technology Society of North America (RESNA). 2022. Position on the Application of Ultralight Manual Wheelchairs [position paper].
2. Paralyzed Veterans of America Consortium for Spinal Cord Medicine (2005). “Preservation of upper limb function following spinal cord injury: A clinical guideline for health-care professionals.” Journal of Spinal Cord Medicine, 28(5):434–470
3. Freixes, Orestes, et al. Wheelchair axle position effect on the propulsion performance of persons with C7 tetraplegia: A repeated-measures study." Topics in Spinal Cord Injury Rehabilitation 28(4) 113-120. (2022).
4. Kwarciak, Andrew M et al. “Evaluation of wheelchair tire rolling resistance using dynamometer-based coast-down tests.” Journal of rehabilitation research and development 46,7 (2009): 931-8. doi:10.1682/jrrd.2008.10.0137
5. Sonenblum et al. Manual Wheelchair Use: Bouts of Mobility in Everyday Life.  (2012).