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Power Wheelchair Suspension: What you need to know and look for?

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Over the past 2 weeks we have talked about drive wheel configuration and some tips on how to decide which option is right for you. This week we are going to discuss power wheelchair suspension.  The suspension can vary from chair to chair even within each manufacturer, but there are some key points that we should discuss. 

Most power wheelchairs on the market are going to use compression springs for their suspension. There are two types of compression spring that are typically used: Linear and Non-linear.

Non-linear springs as seen in the photo below allow for changes in compressive load at different points of the range.  What this means is that you can have the looser spring coils at the beginning phase to help with climbing over obstacles.  The trade-off will be that you will lose some of the overall stability of the chair when not climbing.  Many manufacturers will use one non-linear spring as their suspension.

Linear springs on the other hand allow for consistent stability throughout the compression range.  For Permobil, these springs are also adjustable. The factory will set the suspension spring resistance based on the weight of the user and then the supplier or manufacturer representative will have the ability to further adjust depending on the needs of the user. With the Permobil M and F series, the suspension will be composed of multiple linear springs to achieve optimal traction and suspension.

 

Why does this matter?  The shape and the coil distance have an impact on how a spring works and effects the user.  The better the suspension, the greater the decreased forces on the end-user. This could lead to increased seating tolerance, pain management, spasticity management, and decreases the risk for loss of balance or position in the wheelchair.  One of the biggest points that I think about is driving over any uneven terrain whether it is just a sidewalk or grass at a park. It is important that as the chair goes over each bump that this bump is not felt by the user or limited as much as possible.  If each bump is transmitted up to the user, then the user will likely not maintain their seated position.  They will also feel all this vibration.  According to one study by Wolf and colleagues in 2007, this vibration can lead to many impairments including fatigue and pain.  

 

 

The final thought that I believe is one of the most crucial points to make is that the suspension on the wheelchair should always be there for you or your client.  We know how important suspension is and the negative impact that not having this suspension could be to our clients.  Therefore, we need to make sure that the wheelchair will maintain its suspension in any position and over all surfaces.  No matter what position the user takes the Permobil power wheelchair to, such as elevate, posterior tilt, active reach, or standing, the suspension remains the same.  If you want to drive your wheelchair in elevate, active reach, standing, or other positions, you want to be sure that your suspension will continue to support you in those positions and not lock out. 

It is important to know that each manufacturer will have different suspension set up on their chairs.  As a client, therapist, or carer make sure you ask about the suspension to determine which option is best for you.

 

Rachel

 

 

Part 2: Power Wheelchairs - Where is my Drive Wheel and Why Does it Matter?

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The drive wheel on a power wheelchair is the larger wheel if you are looking at your wheelchair or client’s wheelchair.  The location of this drive wheel can have a large impact on how the power wheelchair drives and manoeuvres in different environments.

There are three main types of drive wheel configurations on power wheelchairs: front-wheel drive, mid-wheel drive, and rear-wheel drive. In this blog today, we will focus on mid-wheel drive. 

 Mid-Wheel Drive:

The mid-wheel drive power wheelchair is the most recent technology developed for power wheelchair bases. It attempts to combine the positive aspects of front-wheel and rear-wheel drive into a hybrid product. Mid-wheel drive has many benefits.  The most well-known benefits being the small turning radius and intuitive driving.  The mid-wheel drive power wheelchair has the smallest 360  ̊ turning radius which can improve manoeuvrability for many individuals in their home or smaller spaces.  The intuitive driving benefit is due to the placement of the drive wheel. Typically, in the mid-wheel drive, the client will be sitting directly over the drive wheel, which is where the chair will turn/rotate from.  This axis of rotation being directly under the individual is what makes the driving intuitive or often people will say “easier to learn”.  It is important to remember that in some cases the mid-wheel drive may not line up directly below the client and therefore may lose some of that intuitive driving.  The final benefit to discuss for mid-wheel drive is the stability.  Because a mid-wheel drive wheelchair has 6 wheels on the ground, this chair will offer superior stability. This can be the case whether ascending, going up, or descending, going down, ramps or inclines. 

 

While there are many benefits for mid-wheel drive power wheelchairs, there are a couple considerations when deciding if mid-wheel drive is right for you or your client.  In being a superior option for stability, the 6 wheels on the ground also means that more energy from the ground is transferred to the client. Imagine going over a bump, because there are 6 wheels you could feel that bump 3 times versus the 2 of the front-wheel drive.  This could potentially limit the ride comfort for the individual in the chair.  Luckily, depending on each manufacturer, we have suspension to help decrease the impact of having 6 wheels on the ground.  I LOVE talking about suspension and we will have a blog post coming soon to talk all about suspension in power wheelchairs and the importance of the suspension.  The other comment I hear about mid-wheel drive power wheelchairs is the potential for “high centring”.  This term is used to describe when the centre drive wheels lose traction and may not be able to move in certain situations. This is particularly a risk with uneven terrain and was previously the biggest disadvantage of the mid-wheel drive power wheelchair. However, depending on your manufacturer, newer technologies and suspension can compensate and have greatly decreased the risk of this occurring.

The mid-wheel drive power wheelchair is the most popular drive wheel configuration and for good reason.  As technology continues to progress, the mid-wheel drive continues to have greater benefits with less limitations. 

Keep in mind that not everyone will benefit from the same drive wheel configuration and it is important to ask questions and complete an evaluation to determine which drive wheel would be best for you or your client. 

 

Rachel

 

 

Power Wheelchairs - Where is my Drive Wheel and Why Does it Matter?

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The drive wheel on a power wheelchair is the larger wheel if you are looking at your wheelchair or client’s wheelchair.  The location of this drive wheel can have a large impact on how the power wheelchair drives and maneuvers in different environments.

There are three main types of drive wheel configurations on power wheelchairs: front-wheel drive, mid-wheel drive, and rear-wheel drive. In this blog today, we will focus on front-wheel drive. 

 Front-Wheel Drive:

The front-wheel drive power wheelchair is typically going to be good for maneuverability indoors and optimal for outdoor use.  This is because of the larger drive wheel being the first wheel to overcome the uneven terrain versus the smaller casters.  Because the front wheels are connected to the drive motors, these pull the casters over obstacles and through various terrains versus if the casters were the front wheel.  In the case of the casters being in front, the casters are being pushed, the force generated is forward and downward.  This would be similar to a plowing effect and can increase the likelihood of becoming stuck in certain situations. For individuals looking to go over all terrains, the front-wheel drive wheelchair may offer the best solution.

Another benefit of front-wheel drive is the smoothness of the ride.  Look at how many wheels are on the ground.  In the case of front-wheel drive there are four wheels versus the six wheels with a mid-wheel drive chair. This means that as the end-user goes over a bump in a front-wheel drive chair, they would feel the force of that bump two times versus three in a mid-wheel drive. This can also be important for individuals that may easily lose their positioning when going over any uneven terrain.

We could talk about front-wheel for hours, but the final benefit to mention is the front-wheel drive chair’s smallest front turning aspect.  In all the configuration options, the chair will turn on its drive wheel.  The photo below shows an example of a bathroom.  In this bathroom the sink is positioned against the wall.  Because the wheelchair turns on its drive wheel and the end-user can only pull themselves so close to the wall before turning, we can see the only chair to gain full access to the sink is the front-wheel drive.  Does this mean that everyone should have a front-wheel drive wheelchair?  No, but it does mean that it is important for clinicians, suppliers, and clients (end-users) to consider the environment that the client lives in. 

 

  

Often, I hear that people stay clear of front-wheel drive because it doesn’t have as small of a turning radius as mid-wheel drive and it is harder to learn to drive.  Both of those statements are true.  The front-wheel drive will have a slightly larger 360 degree turning radius, but as you saw above it has the smaller front turning aspect which may be utilised more than someone turning in a full circle.  Front-wheel drive may be less intuitive to learn how to drive versus mid-wheel drive, but with a little practice and a few key tips, many users find front-wheel drive to be just as easy to learn as mid-wheel.  The two key points I like to teach someone when learning to drive a front-wheel drive wheelchair is:

  1. Hug the corner.  When going through a doorway the end-user will want to “hug” the corner or keep a tight turn.
  2. Turn towards the problem. For example, when positioned adjacent to a wall/barrier, turn toward the wall/barrier, then slightly reverse to allow the rear casters clearance for turning in the desired direction.  This might sound complicated, but if you remember to turn into the problem you will easily maneuver away from the problem.

Keep in mind that not everyone will benefit from the same drive wheel configuration and it is important to ask the questions and complete an evaluation to determine which drive wheel would be best for you or your client. 

 

Rachel

 

Shoulder Prevention: Are we doing enough?

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We have been discussing shoulder preservation over the past couple months and today I want to finish our discussion with this video. When I watched this video, I became overwhelmed with several emotions. I must have watched this clip 10 times in a row. Over and over, each time thinking about all of my clients, individuals with a mobility impairment, but the thought that I couldn’t stop thinking about was – Are we doing enough?

 

 

Watch this video. Watch it at least twice. The first time you might laugh seeing the challenge for the one end-user at self-propelling up the ramp versus the other end-user who is utilising the SmartDrive power assist. The second time you watch this, what do you see?

For me, I see two things. First, a strong woman pushing to her limits to overcome that ramp. She should be proud, as many of us might not be able to accomplish such a task, but I can’t help but also see someone who has to struggle to achieve the same outcome as the person next to them. Every time I watch this video I think about her shoulders, her goals, her independence. Is she able to get everywhere she wants to go, safely and independently? Or, is she limited because of her environment and her equipment? What happens to her shoulders a year from now? 15 years from now? Will she be able to maintain her independence and navigate in all the environments she encounters? Are we doing enough?

 

 

The founder of Permobil, Dr. Per Udden, so perfectly stated, “Every person has the right to have his or her disability compensated as far as possible by aids with the same technical standard as those we all use in our everyday lives.”. I think about this statement, this video, and I know that as an industry we have to do more.

Now, it’s important to say that many end-users may choose to not have a power assist or prefer even if they have one to propel independently up ramps for example, that is their choice and as a therapist we recommend what we believe to be safe and beneficial to the client. However, how many clients are not able to receive the equipment necessary for them to live their lives to this same technical standard? This is where my question comes in… Are we doing enough?

This question is for everyone: The manufacturers, end-users, therapists, dealers, families, and carers. Are we doing enough?

No matter what your role above may be, we all have to work together to make sure that individuals with mobility impairments are receiving equipment that is necessary for them to complete their goals and to live their lives to the same technical standard.

There is a massive task for manufacturers to continually design and develop products to meet these needs and while gaps exist, we see some amazing products coming out to help support individuals with mobility impairments.

Then there is a gap. We often see many of these products, but end-users are unable to access them. This can be for many reasons, oftentimes this can happen from a lack of knowledge of the products, not understanding the client’s needs or goals, limited resources, and limitations of funding.

No matter where this gap comes from, we have to all work together to help close these gaps. During the actual assessment and evaluation this means working from a team approach. If we have the therapist, client, family, carer, and dealer all working together in the assessment we see the best outcomes, but we can’t just stop there.

Funding. This can be a very hot topic around the world. We see countries with funding systems based on the client’s functional needs, the client’s medical necessity, or given an allocated fund that they can use to their discretion. We see funding systems with strict guidelines in what is/is not funded while other systems are open to understanding why the recommended equipment is necessary.

The purpose of this blog is not to discuss funding and it is not to talk negative about any country’s funding system. While we can shift the question to the funding bodies and ask, “Are they doing enough?”, instead I want us to first shift the question back to our industry and ask again, “Are WE doing enough?”.

 

 

As an industry, have we done enough to show the impact that this equipment can have on an individual’s life? How often do we see videos like the one above? Does the funding system understand the impact that a device or piece of equipment can have on an individual’s life? Has this been explained? For many countries this is discussed by the therapist on the request for funding, but what about after? Once the equipment has been approved and delivered, do we show this impact?

Just as in the assessment we work together as a team, we have to have this same team approach if we want the community outside of our small industry to understand.

If you are a therapist this means educating the community, the clients, and the families. Talk about what it is you do and why you do it. Share your stories of success. Work together with other therapists to share your knowledge and experiences. Attend conferences, seminar, and workshops to not only advance your knowledge, but to support your industry.

If you are an end-user, family, or carer – Show and talk about what your equipment does for you! It doesn’t have to be a power assist, this can be your manual wheelchair, your power wheelchair, etc.… We want everyone within and outside of the industry to see the impact that a device or piece of equipment can have on someone’s life. This is how we as an industry become better. This is how we are able to start having those conversations with funding bodies. This is how we can make change happen.

Our world is no longer big. As we continue to progress with technology, we see that our world becomes smaller. We can interact with people across the world. This means that we can work as a team. Maybe you live in a country where you have access to great equipment. Have you thought about how sharing your experiences could help in other countries where funding/resources/awareness is limited?

No matter which part of the team you are, we all have a part to play and just as any team – the more we can work together the better the outcome of success.

If you are an end-user of one of our many Permobil products we want to hear from you! This includes Permobil, TiLite, ROHO, and SmartDrive. Share with us your story of success. Please email Rachel.Fabiniak@permobil.com or your local Permobil Territory Sales Manager.

 

 

Shoulder Prevention: Let’s Talk About Power Assist

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When we are considering a manual wheelchair are we considering a power assist option?


We have been discussing shoulder preservation and how it relates to the weight of the wheelchair, the configuration of the wheelchair and to the individual and their pre-morbid shoulder health. We have also discussed how mobility is NOT and should NOT be exercise. So, how do I know when I should be considering a power assist option? First, we have to look at each individual end-user/client, their goals, environment, and any current shoulder pathologies.

The Goals:

This is one of the most important pieces of information that we need to understand from the assessment. As the therapist we can often just ask the question about what goals the end-user has, but do we really hear all the goals? Often the client may be able to express all of their goals, but just as most of us, we are not always able to express or understand our goals. I like to think about this as when someone approaches me and asks, “Where do you want to be in 5 years?”. This is a difficult question if I haven’t had time to think and prepare an answer and often it is hard to know this answer without having a deeper discussion. This can be the same when talking about goals for the client. If this is someone going into their first manual wheelchair, they may have no idea about what is possible. They may have goals that they want to achieve, but believe it is not an option. Or, perhaps they are not able to even generate a list of goals. They might list a goal or two when asked just to appease their therapist, or just to try to participate. Then we have to think about the clients with cognitive or communication deficits. Does this mean that they don’t have goals? It is crucial that we as the therapist or as any member of the team spend time to discuss goals with the end-user, their carers, and family. Their goals will help us to better understand the needs of their mobility device and if power assist should be considered.

 

 

Environment:

If you are a therapist going into the community, you can see first-hand the client’s home environment but remember there is a lot more to someone’s environment than just their home. I like to think about this like 24-hour positioning. I need to consider every typical environment that the end-user encounters not only just in a one-day time stamp but does this change across different days of the week. Like myself, on the weekdays I may only encounter my home, car, and work environments, but on my weekends, I prefer to spend my time outdoors. As a therapist, it is important that we are able to ask the right questions to better understand the environments that will be encountered.

Shoulder Pathologies:

Have you ever asked someone if they are in pain and they respond no, but then within minutes you find out they take pain medication daily? There are many reasons that pain is not discussed during an assessment. This can range from the question not being asked, the client not wanting pain to keep them from their goals or activities, the client may forget that they are taking pain medication, etc…. No matter what the reason is, it is crucial to determine if the client has any underlying shoulder pain or pathologies. This doesn’t mean that they are not appropriate for manual mobility, but it does help to determine if a power assist option should be considered. 

 

 

While there are still many other important aspects of the assessment to consider, this is a good starting point. Take this information you gather from the assessment and determine if the client is at a risk of further shoulder pain/problems, not being able to navigate in their environment, or if they are not able to achieve their goals without the use of a power assist device. If the answer is yes to any one of these, then discuss with your client and dealer/supplier power assist options.

I often hear that therapists just don’t think about it during the assessment of trial. I know there can be a LOT to consider, but power assist can truly change a client’s life.

Shoulder Preservation: Functional Mobility versus Exercise

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As we continue our discussion on shoulder preservation one common question that comes up from therapists, end-users, and families frequently is: Should Propelling a Manual Wheelchair be Exercise?

This question comes in many forms. Often the therapist has the dilemma of worrying about the end-user being as independent as possible, the idea of maintaining the end-users’ function, and keeping in mind the costs associated with different product options. I have also heard a few therapists’ express concerns that if their client does not maintain an “active lifestyle” they could gain too much weight and not be able to fit into their system. The end-users and families usually tell me that they are concerned about the idea that “if they don’t use it, they will lose it”. This is a common statement that we as an industry made popular and unfortunately continues to be used every day.

 

 

Let’s now go back to the question: Should Propelling a Manual Wheelchair be Exercise? To answer this, we must start by defining what functional mobility is. Functional mobility is the ability for someone to move around in their environment. We ALL have to move around in our environments, whether it is our home or community, to be able to complete all of our daily activities. For an individual with a mobility impairment, this might mean that you need a walker, orthotics, or for this discussion, a manual wheelchair to move around in your environment.

Using myself as an example – for me to complete my daily activities I will move around by walking. This is not exercise for me. I need to be able to move around all day. Now imagine if I had to skip or run every time I moved. This would be not only exhausting, but also a lot of work for my body. I would likely not be able to complete all the tasks or participate in all the activities that I wanted to each day if I had to skip or run everywhere. Therefore, my options would be to either rely on someone else to help or I would simply not be able to participate.

Keeping this theory in mind, the same thought process should hold true for a person who uses a manual wheelchair as their means of mobility. If it is exercise to propel the chair, then you can become exhausted before the day even begins. You might not be able to participate in certain activities or engage in your community if you are exhausted because you are constantly “exercising”. What happens over a period of time to the shoulders? Are the shoulders meant to be exercising this many hours a day?

Functional Mobility should not be exercise! Functional mobility is a right for all of us, no matter what form of mobility we use. Pushing a wheelchair can be exercise, like a brisk walk or jogging. But remember, not all able-bodied people choose this as their exercise. Also, the upper limbs are more vulnerable to injury than lower limbs so “pushing for exercise” needs to be done in a way that does not present a danger of upper limb injury.

So, am I saying that no one should be in a manual wheelchair? NO! Instead, what we need to do is consider the individual, their environment, and their goals. Many end-users are able to propel their manual wheelchairs throughout the day, but some end-users may be working too hard to complete this mobility. In this case, we need to consider other options to help the end-user preserve their shoulders, reach their goals, and maintain their independence. Next week we will discuss one of these options – Power Assist!

Per Udden, the founder of Permobil, said it best:
“Every person has the right to have his or her disability compensated as far as possible by aids with the same technical standard as those we all use in our everyday lives.”

 

Rachel

Pneumatic Tyres Versus Solid Tyre: An End-Users Perspective

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A critical part of a wheelchair, by definition, is the rear wheels and a critical part of the rear wheels is the type of tyre used. There are pros and cons for different tyre types. Rachel asked me to write about my experience with pneumatic and solid tyres, so here goes.

In my earlier years as a wheelchair user I used pneumatic tyres. One of the things that was a party spoiler was flat tyres. I had a bag that used to hang off the back of my chair, and it always had a spare tube and some tyre levers in it. But it was a hassle, for myself and my friends, and after a while I got sick of flat tyres. Plus, I had started travelling and just wanted the security and convenience of no flats. So, at some stage, I switched to solid tyres.

 

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I rolled on solid tyres for a lot of years. I got used to them, and they worked well. They were hard work when I needed to change them, but I felt secure with them. I was playing wheelchair basketball at the time and was using high pressure pneumatic tyres on my sports chair. The difference in roll resistance was significant, but for everyday use I just preferred the security that solids gave me. Then, about 12 years ago, a range of puncture resistant tyres became available in Australia. They claimed to be able to resist punctures from thumb tacks, and a few of my friends were using them so I decided to give them a go.

When I changed to these pneumatic tyres and pushed my chair again it was like a new chair, it was so much easier to push! I was really shocked at the difference. Research that compares pneumatic and solid tyres confirms the significant difference in performance between the two.

One paper which supports this is “The ergonomics of different tyres and tyre pressure during wheelchair propulsion” by BONITA J. SAWATZKY and Co. in Nov 2004 which found that “Choosing solid tyres instead of pneumatics puts those using the wheelchair at potential risk. Pneumatic tyres showed no statistically significant difference in rolling resistance until pressures had decreased to 50% of the recommended value. The performance of the solid tyre was worse than that of the pneumatic tyres even when they were inflated at 25% of the recommended pressure.”

I have been using them ever since, and they have proved to be sufficiently puncture resistant for my use. Even though they are more expensive than non-puncture resistant tyres they have proven to be longer lasting which makes them a better economical option. I have had only one puncture in all the time I have used them. Being brutally honest with you, I am not the role model wheelchair user when it comes to doing maintenance. For maintenance on pneumatic tyres I have a rechargeable cordless compressor which I use regularly to make sure there is sufficient air in the tyres. Changing tubes and tyres is not on my list of things I want to do on any day, besides which I suck at it. I have pinched more tubes than I would care to mention. So, any new tyres/tubes I need are now supplied and fitted by my local bike shop. If you live close to a good wheelchair dealer, they should also be able to do this. In saying this, for a vast number of wheelchair users, changing a tube and tyre is a quick and easy process.

Depending on a wheelchair user’s environment and daily activities, puncture resistant tyres may not be required. In this case economical tyres might be a better solution.
On the other hand, some people will require more puncture-proof resistance than any pneumatic tyre can provide. For example, people living in rural areas that come into contact with “three cornered jacks” or working in environments where there are nails and the like. In these cases, the compromise in performance can be justified and solid tyres may be the best option. And, for a lot of users, the absolute confidence solid tyres give them is worth the loss in performance.

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Some final thoughts, overall solid tyres are heavier than pneumatic tyres. There are different types of solid and pneumatic tyres and, in my experience, it has been worth spending a little more on good, quality tyres. The increased life of better-quality tyres usually means it is more economical in the long run. I would also not recommend solid inserts in pneumatic tyres. They are heavy and do not perform as well as other options.

Mal

 

The Weight is Not just Coming from the Frame

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We just finished last week’s blog talking about the differences between titanium and aluminium, one of those differences was the weight of each metal. In our continued discussion on shoulder preservation, we know that weight can be an important factor when propelling a manual wheelchair all day. Remember studies show that the average full-time manual wheelchair user completes 2,000 to 3,000 pushes every day! This is an enormous amount of work that we are asking the shoulders to complete. Therefore, weight is important. However, weight does not just come from the frame.

 

 

We can have the lightest wheelchair frame, but if we load it down with armrests, heavy cushions and backrests, solid tyres, etc… we just cancelled the weight we saved in choosing a lighter-weight frame. It is important we think about the components that we are putting on the wheelchair. With each component that we add onto the chair, we should ask ourselves, “What is the purpose/goal of this component?”. Let’s think about a few examples when it comes to an individual who is a full-time upper extremity propeller in a rigid manual wheelchair.

One of my favourite ways to decrease weight is to consider the armrests. What are the armrests doing for my client? Perhaps the end-user needs to have armrests to complete a functional activity, but more than often I see that the armrests are placed on the wheelchair for “comfort” reasons. How much weight does this comfort option add onto a wheelchair? It is not just the armrest itself, but also the large brackets required to mount these armrests to the wheelchair.

What about the wheels and tyres? This is another way that we can substantially increase the weight of a wheelchair. We often forget about how much a wheel and tyre can weigh. The position of the wheel and tyre is also a key. The further from the end-user the more impact the weight will have on propulsion. So, now if we think about the wheels and tyres and their location, we begin to understand the importance.

Does this mean that everyone who is a full-time manual wheelchair user should have pneumatic tyres and Spinergy Carbon Blade wheels? No, but it does mean that a discussion on goals and how this relates to the wheels and tyres is crucial. Therapists are often nervous about recommending pneumatic tyres for manual wheelchairs, but we want to help decrease this fear and will have a discussion in the upcoming blogs on the truths and myths of pneumatic tyres.

It is important to remember that even small changes can make a big difference. This should be considered in two ways. First, remember you can slowly start to work on decreasing the overall weight of the manual wheelchair, you don’t have to change the whole wheelchair in one day. This is also important for reason 2. Even the smallest changes could feel like a big change to the end-user. Everyone, whether you are the therapist, dealer, or end-user, has to remember that any change to the wheelchair will take time to get used to and may need further adjustments in the future.

As the therapist or end-user should you have to know all the different components available and their corresponding weight? No! You need to know your goals and/or the goals of the end-user. Then, it is the role of the dealer to help determine which products meet those goals and provide options. The dealer can help to discuss the options to decrease the overall weight of the wheelchair. The less weight on the chair, the less demand we place on the shoulders, right? This is absolutely true and should be considered for all individuals who are full-time upper extremity propellers, but if we don’t have the proper configuration, then even the lightest-weight wheelchair will be difficult to push.

Remember that if we all work together as a team, we can achieve the best results!

If you are interested in understanding more about this topic and how the weight distribution on the wheelchair matters, email me to set up your Materials Science for Manual Wheelchairs course.

Rachel

 

 

Materials Matters: Titanium verses Aluminium Manual Wheelchair Frames

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Malcolm’s perspective:
Right from the get-go let me say, I love titanium! From my first ride in a titanium chair some 15 years ago I remain convinced it is the best material on earth for wheelchairs. The ride in a titanium chair feels different, it has a dampening effect on bumps. When I got my first titanium chair my wife would often get surprised when she realised, I was beside her – she could hear my aluminium chairs coming as they went over the tiles and floorboards, but not the titanium chair. This was because of the vibration dampening. Apart from the “ride”, I love the fact it does not have to be powder coated, which means it does not chip, or look scratched and old. As well as that, titanium is strong – the strongest weight to strength ratio of any metal – which suits my lifestyle which involves lots of travel. After 15 years of regular plane trips I have confidence that when I arrive my chair will be good to go despite the rough handling it gets. That peace of mind is really important to me.

 

 

My chair is also ultra-light, especially with a non-folding back. With the configuration I have it is slightly under 8kg with the wheels on, about 4.5kgs with them off.
A couple of things to note, not all titanium is the same, so the type of titanium and the thickness of the tubing will impact on how the chair rides and how heavy it is. Also, my chair frame is made from titanium, but I have carbon fibre components such as side guard, wheels and backrest. Some of the parts are aluminium, such as front forks and camber clamps, so it is really a titanium frame with hybrid components.

Rachel’s thoughts:
Mal just gave a great insight into his preference. Now, let’s look at the materials and why Mal has preference for titanium versus aluminium. We have been able to learn a lot about the materials we use in manual wheelchairs through other industries, one of the big ones being the biking industry. We will start with aluminium. All types of aluminium have specific strength, low density, and resistance to corrosion. There are lots of different types of aluminium, but most manual wheelchairs are made of either 6000 or 7000 series aluminium. Many people believe that 7000 series is the best, just like how the iPhone 10 is better than the iPhone 8, but this is not true. The type that is best depends on how each manufacturer wants to use the aluminium. TiLite uses 6000 series as this allows for the aluminium to be weldable and for the greatest amount of customisability while still having a high strength. The 7000 series has a slightly higher tensile strength, but it is heat treated and therefore is harder to machine and less customisable. The difference in strengths of aluminium is minimal as compared to the difference in strength of aluminium to titanium. You can see the difference in the chart below. The chart on the left showers the ultimate strength of 6000 series aluminium, 7000 series aluminium, and then titanium. The chart on the right shows the strength-to-weight ratio.

 

 

Titanium has the highest strength to weight ratio of any metal on Earth. This gives the end-user a light weight and strong frame. Titanium is virtually immune to corrosion and is easily machined. From its ability to be easily machined and its strength to weight ratio, and vibration dampening properties, Titanium can allow us to achieve that ultimate fit. This ultimate fit along with the design of the frame of the chair leads to the optimal ride for our end-user. Although titanium has many benefits, it is a more expensive metal, and therefore the base price for a titanium frame will be more than an aluminium frame.
When deciding what type of material is right for you or your client, it is important to assess each person individually and consider the environments in which the chair will be used. It is also important to keep in mind the amount of time that will be spent in the wheelchair. We know that vibration has negative impacts on our health, and we know titanium through its material properties, design of the frame, and being easy to machine, will help to limit some of these vibrations, therefore providing the highest performance and ride for the end-user that is in the wheelchair throughout the day. We also know that strength is important as we want the frame to be able to withstand the environment that it is taken through. Finally, we want to think about the weight of the overall chair and how we can keep the weight low. This will help reduce the amount of work that we are asking the shoulders to do with every push. This is where are shoulder preservation comes back in! We want to make sure we can keep the chair as light as possible. This doesn’t just include the frame! We also need to think about what we are putting on this frame. All of the seating components, accessories, tyres, wheels, etc… have an impact on the weight of the wheelchair. Besides what goes on the wheelchair, we will also have to consider how the frame design impacts the ride, strength, and way that the wheelchair is built. We will continue this discussion next week.

Shoulder Preservation: An End-User Perspective – Mal’s Story

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In 1980, when I acquired my SCI, there was very little talk about preservation of shoulders. The focus was on strength, lots of weights and pushing. The adage “if you don’t use it you lose it” was strongly endorsed. In those days, I thought that shoulder pain was a good thing, it meant I had been working my shoulders and therefore strengthening them. In my mind it was “a badge of honour” to have sore shoulders. I didn’t know the difference between “good” pain and “bad” pain. In the early 1990s, I started playing competitive wheelchair basketball. Here I began to learn more about how to look after my shoulders – resistance bands, stretching, warming up, warming down, backwards pushing rotator cuff strengthening, etc… I also started handcycling and concentrated on the “pull” of the hand cranks to work the back of my shoulders. But, to tell the truth, my focus was so much on being competitive I often played with injuries, which I am sure has caused problems for me now. Hindsight is a great thing, and I wish I had of thought more about the long-term impact of the stresses I put on my shoulders, elbows, and wrists. Pain, loss of strength, loss of range and carpal tunnel syndrome are things I have experienced and continue to work against. At 39 years post injury, I am still mobile, and the past several years I have put into place strategies to maintain and improve the health of my upper limbs.

 

 

Apart from the obvious negative of pain, why is upper limb health so important to me? There are many reasons, but for the sake of this blog here are three of my main ones

Independence: A friend of mine often says that “if it goes without saying, it is worth saying”. My shoulders are fundamental to my independence. Being able to push my wheelchair, transfer, lift my chair in and out of the car, kayak, complete pressure reliefs – just about every activity of daily living (ADL) I do requires my shoulders.

Wellbeing: Being able to do all the things I can do independently has a huge impact on my        wellbeing. My SCI has cost me a lot of independence as it is, so I treasure every bit I have. Loss of independence is, quite frankly, depressing! As well as that, pain is a stressful thing, so minimising pain is really important.

Pressure Care: My shoulders are directly linked to my pressure care. In the past 39 years I have had only 2 pressure injuries which caused me to spend time in bed. One was post operation, the second was a stage 2 pressure injury caused by a bad transfer. The better my shoulders are the better my transfers are, and the less risk I have of a pressure injury.

So, as I race into my sixties and hopefully beyond, what are my strategies for looking after my shoulders? Here are some of the things I have done, and am now doing

My wheelchair is super light-weight and custom built around me. I have minimal adjustment and folding parts in my chair. After 39 years I pretty much know what I want out of my wheelchair, so a fixed back and fixed front to rear height is my preference. Even these simple things shave a noticeable amount of weight off my chair. I have the rear wheels as far forward as I feel safe with which makes it easier to push.

I restrict my pushing to areas that do not cause a lot of shoulder pain. I have been using a power assist device, the SmartDrive, for many years now and love it. I use it for any steep hills or really long pushes. I still push, but not as much and on less challenging slopes.

I have a set of strengthening and stretching exercises that I do regularly. Most of these involve resistance bands or a medicine ball, and are low weight with higher reps. The important thing is for me to concentrate on technique! They are exercises recommended by        my physiotherapist. As part of my NDIS Capacity Building, I have linked my goals of maintaining independence and function to the cost of the physiotherapist.

For cardio exercise, I rely on kayaking and handcycling. Both these activities allow me to focus on working the back of my shoulders, in the “pull” stroke.

I have been using an ergonomic hand rim for about 15 years now. These significantly improved my carpal tunnel issues. There are a number of these available, including the  Natural Fit™ and the Flex Rim™ (my favourite).

This is a little left field, but it has been an important change for me. Up until about 10 years ago I did not have wheel locks on my chair. With the improvement in design, specifically scissor locks, I finally decided to try them. It amazed me how much easier my transfers became!

 

The conversations I have with a lot of my peers these days centre around what we are doing to maintain shoulder strength and the impact long-term wheelchair propulsion is having on us now. If I could have a chat with my 20 year old self I would stress the importance of looking after his shoulders (not that he would have listened). In my mind the old adage of “use it or lose it” has been changed to “use it, don’t abuse it”. There is a lot of great Assistive Technology and resources to help wheelchair users maintain upper limb health, so why not take advantage of it all!

 

Malcolm Turnbull