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The Ergonomics of Wheelchairs

by Gary Karp,
Adjusting your chair for the right fit - and using it well - has a lot of effect on your health and comfort.

Ergonomics, technically, is about the relationship of the body to work. It has long been a priority in industrial settings like assembly plants where work injury from physical overuse is a great danger. Now that computers are causing a lot of physical discomfort, the term is more widely heard.

What does it have to do with wheelchair users? Well, ergonomics is really about using our bodies safely and efficiently, in a way which doesn't strain our tissues. A way which is comfortable. When we're working, cooking, driving, creating. Wheeling.

And it's about using the proper tools in optimal fashion. Your physical relationship to the tools you use – namely your wheelchair or mobility scooter – determines a lot about how you are going to use your body.

Think of yourself as having a lifetime quota of muscle capacity that you want to use carefully - to spend like it was precious currency. In the context of disability, when you drive a wheelchair – perhaps with limited upper body balance – the potential to overuse your muscles is considerable.

Ergonomics deals with four key criteria. Force. Repetition. Duration. Posture. Let's consider how they apply to wheeling.

Force. Excessive impact jolts our joints and causes our muscles to tense in response. Some wheelers snap their arms at the end of a push, which puts force on the shoulder joints. If you are able to do a wheelie over a curb, do you land with impact, or do you let yourself over the edge gently? Going over a significant bump at too great a speed in a power wheelchair or scooter can result in unnecessary impact.

Repetition is a pretty obvious one. How many pushes does it take you to travel a given distance? Take better advantage of coasting (which means keeping your tires inflated and your chair well maintained) and consider going a little slower (it takes more pushes to go faster).

Duration refers to continuous muscular effort. It doesn't have to be heavy lifting. Small exertions continuously held are as stressful to your tissues as brief, heavy effort. Leaning on armrests – often because of a poor relationship to your seat and back – putting continuous load on your shoulders is an example of doing "static" exertions. Poor posture is a duration overexertion. If you slump or lean forward, your trunk and neck and shoulder muscles have to do a lot of continuous work. But the real key here is movement. You will not be continually exerting muscles if you are active and changing your posture throughout the day.

Which brings us to posture. People often spend a lot of time leaning on armrests or a table exactly because they are not being supported with good posture in their chairs. This is a matter of seat angle and back angle, adjusting them according to your body shape and your degree of upper body balance. Poor seating makes you slump, trying to get stable. The optimal posture is more upright, allowing your spine to support you. It’s a structural column – that’s what it’s intended to do.

Seat depth is involved here, too. If your seat is too short for your legs, then you are being robbed of the greater stability that comes with full contact between the seat and your legs.

Perhaps you have psychological resistance to good posture because your mother and teachers nagged you about it when you were young! Don't let that stop you from getting the right wheelchair, and ensuring it is adjusted properly so your spine is naturally aligned. It will reduce your risk of spinal curvature, spare your body from unnecessary muscular effort, and preserve your energy throughout the day.

Perhaps the most important relationship between your body and your wheelchair is the position of the wheels relative to your hands and arms. If you are sitting to high above the wheels, with your arms nearly straight, you won’t be able to take advantage of your arms as you push. This will force you to do it mostly from the shoulders – a situation that is all but guaranteed to cause injury. If you are sitting too low relative to the wheels, your arms will be forced up too high as you grab the rim to start the push, which prevents your arms from moving in a natural range of motion and makes pushing more difficult. In general, it should be possible to grasp the wheel at the "ten-o’clock" position and apply force through the push all the way to two-o’clock.

Basically, ergonomics is about comfort. Choose, adjust, and use your wheelchair with that in mind, and you'll reap the benefits of optimal health and activity.

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