Set Up and Adjustment
The many hours you will spend in your wheelchair dictate that you should customize it to fit your body. A properly adjusted wheelchair will be more comfortable to sit in, easier to maneuver, and less stressful on your muscles and joints during propulsion. Your wheelchair setup drastically affects your comfort, posture, stability, and ability to use your wheelchair efficiently and effectively.
In a properly adjusted wheelchair, you should be sitting with the best posture that is comfortable for you in order to optimize your function, while preventing pain or deformity. You should have enough room for your knees to fit underneath most table tops. Your foot supports should be high enough off the ground to avoid hitting obstacles in your path. Make sure your wheelchair cushion, back support, and other positioning aids are in place when you make the adjustments to your wheelchair. The position of the rear wheel will dramatically change how hard you are working to push and will impact the long term functioning of your shoulders.
Changes to your wheelchair – One change to your wheelchair will affect the fit of all the other components, so be prepared to spend a fair amount of time on this crucial operation. Ideally, you should enlist the help of an ATP/SMS , certified by the Rehabilitation Engineering and Assistive Technology Society of North America (RESNA), when adjusting your wheelchair.
Wheelchair mobility – Whenever you alter the setup of your wheelchair, check your forward, side-to-side, and rear stability with a spotter to make sure your wheelchair performs the way that you want and that it is not too tipsy. (Section 1.4 Learning Your Limits describes how to experience your limits of stability). After each adjustment, test drive your wheelchair on ramps, different surfaces, and side slopes to make sure your mobility needs have been met.
As with automobiles, enterprising inventors have developed many different styles and models of wheelchairs. Each is designed for a different purpose and permits different types of adjustments to be made. There are two basic categories of manual wheelchairs: standard use wheelchairs and rehabilitation wheelchairs.
Standard wheelchairs, also known as depot or institutional wheelchairs, are the no-frills, chromed, steel, or powder coated aluminum workhorses usually found in hospitals, nursing homes, and airports. Standard wheelchairs are designed to be simple to use and durable enough to survive within an institutional setting. The arm supports and foot supports of standard wheelchairs are often welded to the frame and cannot be adjusted or removed. The same standard wheelchair is frequently used by more than one person. Standard wheelchairs are usually sufficient for short-term or infrequent use. They offer the least flexibility in adjustment so they may not be the correct size or configuration for the user. Changes and adjustments must usually be made to standard wheelchairs by replacing components.
Rehab wheelchairs are typically ordered and sized to meet the needs of a specific user. They are generally, but not always, built for a user that depends on the wheelchair full time for mobility. Rehab chairs are generally much more durable than standard wheelchairs so that they will hold up to use in all sorts of indoor and outdoor environments. Rehab chairs are designed and built to be either folding or rigid with a folding back support. The arm supports or skirt guards and leg supports are often adjustable in position and removable to facilitate transfer in and out of the wheelchair. Some rehab wheelchairs have adjustments that can be made to change the back support height or angle, rear wheel fore aft position and height and front caster angle. Most rehab wheelchairs are often lighter in weight to make them easier for the user to get the chair in and out of a vehicle.
Vertical axle adjustments on Rehab and Standard wheelchairs
Some standard and most rehab wheelchairs offer several vertical adjustment positions for the front and rear wheel axles.
Moving the rear wheel axle up or down will change:
- The seat height
- The seat plane angle
- The back support angle
- The angle of the caster wheels
- The orientation of the frame
- Your ability to reach the handrims
Types of options available on Rehab and Standard type wheelchairs
- Type of back support
- Type of foot support positioning
- Arm support type
- Wheel-lock type and position
- Rear wheel type (e.g. spoke wheels vs. mag (plastic) and size (20”, 24”, 25”, 26" or 27”)
- Handrim style, outside diameter, grip diameter, material, shape and method of attachment
- Caster wheel type (e.g. solid versus pneumatic) and size (4”, 5”, 6” or 8”)
- Frame color
- Upholstery color and type
Additional types of adjustments available on Rehab wheelchairs
The most common adjustment that is available on a wheelchair is the fore aft and/or vertical adjustment of the rear axle. This allows the adjustment of the seat height and/or angle which can improve the ability to reach the handrims. Changing the seat angle can also improve the stability and/or function of the user in the chair. Multi-adjustable wheelchairs often have one or more of the following adjustments and/or options available:
- Vertical and horizontal rear wheel position
- Seat support angle and or height
- Front caster position and angle
- Foot support angle, length and or position
- Lower leg support angle
- Back support height and or angle
- Wheel lock position and type
- Seat width and or depth
- Rear wheel camber from vertical to angled out at the bottom
- Arm support height
This training guide describes the proper fitting parameters for each adjustment later in this chapter. Changing or adjusting one part of your wheelchair often changes the position of another part. You will probably have to perform a series of adjustments to achieve the correct fit.
Other types of wheelchairs
Add-on power systems
Some add-on power systems require removal of the main drive wheels. Wheels with motors in them are then attached to the chair to amplify the push of the wheelchair user. In this case the handrim is essentially a switch that tells the motors to propel forward when the user pushes on the handrim. The system adds weight to the wheelchair. Batteries must be carried on the wheelchair as well.
Some add-on power systems attach underneath the wheelchair frame and have a separate wheel that touches the ground to power the wheelchair. The Smart Drive™ is a power drive unit that attaches underneath the wheelchair. It senses when the wheelchair user pushes forward on the handrims of the chair and powers the chair to match the strength of the push that the user applies to the handrims. The battery slips under the seat where it hangs on the seat upholstery.
Arm crank wheelchairs
This can be added to a standard manual wheelchair. When the crank drive is attached to the wheelchair it lifts up the front casters of the manual wheelchair. Some wheelchairs are designed for crank driving only.
These generally have higher seats with very little seat dump, highly cambered main wheels, with a wrap-around frame in the front of the chair to prevent entanglement with other basketball chairs.
A wheelchair designed to negotiate sand and soft surfaces. Usually has wider, balloon tires often with large tread and a long wheelbase to provide added stability.
Lever drive wheelchairs
Some lever drive systems can be retro-fitted onto a standard manual wheelchair, others are designed and manufactured for lever drive use only and have no handrims. A lever drive chair can increase the leverage that can be applied to push the wheelchair forward.
Hemi-height refers to a low floor to seat height. Wheelchairs are sometimes set-up with a “lower” seat to floor height to allow a person with hemiplegia to use one hand and one foot for self-propulsion. This style wheelchair is thus often referred to as a “hemi-wheelchair”.
An off-road wheelchair has large knobby tires similar to those on a mountain bike and is designed to negotiate rough terrain and unpaved surfaces. The wheelbase is generally longer and, wider which makes it more stable. The rear wheels are generally highly cambered making it even more stable. The front wheels are connected with a tie-rod, but not always. Many off-road wheelchairs have hand operated, dynamic braking and active suspension systems.
One arm drive wheelchairs
These chairs are designed for users that only have the use of one arm to both propel and steer the wheelchair. There are two types of one-arm drive wheelchairs One type has two handrims attached to one wheel. The outside handrim controls the opposite wheel and the inside hand-rim controls the wheel on the same side. With a collapsing scissor drive chair the wheelchair can still fold.
The other type has a lever to drive and steer the wheelchair. Using the left or right hand as ordered, the lever is pumped forward and backward to propel the wheelchair. Twisting the handgrip left or right turns the chair. Some one arm drive wheelchairs use a spring loaded bar that has to be removed from the wheelchair in order to fold the chair for transport.
These chairs are transfer chairs used by a wheelchair user to roll down a ramp into a swimming pool. These chairs are designed to roll into the water and are often constructed of stainless steel or plastic. Most of these chairs have hard solid plastic seats and removable arm supports. They are most often self-propelled with push handles.
Quad rugby wheelchairs
These have a lowered seat height with significant seat dump for postural stability and have cambered rear wheels with a shorter wheelbase for the forward players. The chairs for defensive players have extended foot supports to block other players. The chairs have spoke protectors and a protective cage around the front of the wheelchair.
A lightweight, three-wheeled wheelchair designed in an aerodynamic shape to maximize traveling speed. Used for training and racing events that take place on tracks or on roads.
On a recliner chair, the backrest position is easily adjusted relative to the seat; such that when “fully reclined” the backrest and the seat are continuous in a horizontal position – allowing the rider to “lay down” or “stretch out”.
Recliner wheelchairs are most often used by people who use gravity to help balance their trunks, cannot maintain an upright sitting posture, have limited movement at their hips, or need to recline in order to relieve pressure from their buttocks. The rear wheels on recliner wheelchairs are further back, making the wheelchair more stable (harder to tip backwards). It also makes it harder to reach the handrims to propel. The wheelchair may have anti-tip devices installed to prevent the chair from tipping over backwards. Anti-tip devices are small-diameter wheels that attach at the back of the chair to provide additional rear stability.
Shower chair wheelchair
Shower chair wheelchairs are either stainless steel or plastic and are designed for toileting and showering. They usually have a commode style seat and can either be rolled over a toilet or used as a commode with the commode pail in place. They are designed to roll into an accessible shower. Shower chair wheelchairs usually have standard wheel locks, and removable or swing away arm and foot supports. They are made in self-propelled and attendant propelled versions.
These allow the user to achieve a standing position. Most standing wheelchairs are mobile in the sitting position and when they raise to the standing position are not mobile. Some are mobile in the standing position also. They are usually used to access various locations, but there are numerous physical benefits to standing, including: stretching of the muscles, loading the bones, draining the bladder fully, and allowing internal organs to change position from sitting.
This is designed for playing tennis and other racquet sports. Generally with significant rear wheel camber for increased lateral stability. The user general sits in a very compact position to reduce the moment of inertia for quicker turns. Tennis chairs usually have one or two front casters and sometimes a single anti-tip wheel in the rear.
These allow the user to change the orientation of the seat on the frame by allowing the entire seating system (the seat, back and foot support) to tilt back. This allows for a mechanical weight shift to provide increased postural stability and can provide an effective pressure relief. Tilt-in-space wheelchairs require a long wheelbase for stability. This decreases the maneuverability of the wheelchair.
Wheelchair Component Selection
Most manual wheelchairs feature these basic components:
- Rear wheels
- Front caster wheels
- Solid/pneumatic tires
- Arm supports
- Arm support panels or skirt guards
- Foot supports
- Wheel locks
- Sling or rigid back support
- Sling or rigid seat support
The materials, design, and adjustment of these components will affect your wheelchairs performance and fit. This training guide describes the proper adjustment and fitting of your wheelchair.
Many types of rear wheels are available for manual wheelchairs. Most are either mag or spoke. Mag wheels are usually made from hard plastic and typically have only five or six molded ribs between the hub and wheel rim. Mag wheels are virtually maintenance-free and more durable than spoked wheels, but are usually heavier. There are now lighter weight and flexible fibers being used for spokes.
The spokes on a spoked wheel keep the wheel round. The quality of spoked wheels has improved; however, spokes can loosen, break, or fall out. If spokes break or fall out they must be replaced to keep the wheel round. Spokes should also be checked for their tension as uneven tension will also cause the wheel to go “out of round.” The same wrench used to tighten bike wheel spokes can be used on wheelchair wheels. A good bike shop can usually help true your wheels to be round and planar with the spokes evenly tightened. The range of options in spoked wheels is quite large – reflected in the wide price range of spoked wheels. The goal is to find the diameter, size and tread pattern you want with the lightest weight and durability required to fit your lifestyle and propulsion demands.
The diameter of the rear wheels affect how your wheelchair performs. In the past, the standard rear wheel diameter has always been 24 inches. Now it is common to see 25-inch diameter rear wheels. Taller wheelchair users often prefer 26 or even 27-inch diameter wheels. Smaller rider’s, those with shorter arms, may benefit from smaller wheels like 22”. The wheel’s size determines the handrim position in relation to your hands, affecting your ability to propel the chair efficiently, using less effort. You should be using the wheel size that is appropriate for your size, so people with longer arms (taller people) are often more comfortable and efficient pushing on larger wheels. Larger wheels roll over obstacles and rough terrain easier and may improve wheeling efficiency for you.
Rear wheels with quick-release axles allow you to detach your rear wheels in a few seconds without tools for transport or storage.
Rear tires for wheelchairs are either air-filled (pneumatic) or solid (flat-free or airless). Pneumatic tires require a specific air pressure to provide optimal performance. On uneven and outdoor surfaces, pneumatic tires usually give a more cushioned, smoother ride and are easier to propel than solid tires. If you only use your wheelchair on hard, smooth surfaces, solid, flat free, or semi pneumatic tires may make your wheelchair easier to propel. However, the tread on pneumatic tires tends to wear out more quickly than the tread on solid ones. If you have pneumatic tires, you may want to carry a patch kit, pump, and/or spare tire tube at all times to avoid being stranded by a flat. Pneumatic tire rims can be filled with solid inserts instead of tubes providing a tread to reduce slippage when wet while benefitting from the advantages of a maintenance free tire. Note that a flat free filler provides a firmer, stiffer ride than an air-filled tire. Some inserts take away some of the cushioning properties of air-filled inner tube tires.
Solid tires are filled with a foam core or another type of flat-free insert. Solid tires only need to be replaced for tread wear. Because solid tires are stiffer than pneumatic tires they usually have less shock absorbing capabilities and they give a bumpier ride over uneven surfaces. If you only use your wheelchair on smooth, hard surfaces, solid tires can make rolling your wheelchair easier.
Tire tread also affects your wheelchair’s performance. Knobbier tires perform better on rough terrain because they provide more traction. The same knobby tread that grips so well also tracks more mud, snow, and dirt inside than smooth ones. Unless you plan to wear gloves and push on the tire, select knobby tires that do not have the knobs on the side where they will rub against your hands when using the handrims. Knobby tires also require more effort to propel over smooth surfaces than smooth tires. Smooth tires are more maneuverable over hard, flat surfaces, but make rolling over rough terrain more difficult.
The handrim is usually attached to the wheel near the wheel’s rim. A spacer on the bolt attaching the handrim to the wheel gives you room to grip the handrim with your fingers. You can use a shorter spacer to bring the handrim closer to the wheel. This narrows the overall wheelchair width but may make it more difficult to get a good grip on the handrim. If the space is too large, you may catch your thumb in the gap.
Hand rims are available in a variety of materials and styles. Metal handrims are sometimes difficult to use because they are slippery and get very cold, especially in winter. Rubber coated or textured handrims might improve your grip and allow you to push more strongly, but the extra friction will cause your hands to burn when going downhill. Because of this problem, coated handrim users usually wear gloves to push their wheelchairs. The coating can also wear off with repeated scraping against obstacles like wall corners and narrow doorways.
Handrims with projections can make it easier to push with less hand function. Handrim projections are often available angled more vertically or horizontally to accommodate different pushing styles.
A variety of ergonomic handrims are now available. Be sure to try them out. Choose ones that are comfortable for starting, stopping, and turning on flats or hills. Traditional handrims require a strong grip to push up a hill. When shopping for ergonomic handrims choose ones that minimize the amount of grip strength that is required to push your chair on soft surfaces and up hills. This will reduce the repetitive stress and strain on your hands over the long term. The addition of ergonomic handrims is perhaps the greatest improvement you can make to your existing or new wheelchair. Ergonomic handrims that are flexibly attached to the wheels will flex absorbing shock during propulsion and allow you to squeeze through narrow doorways as well.
Wheel locks are sometimes just called brakes or parking brakes. Wheel locks are generally available in low- and high-mount versions and are selected when you order your chair. Low-mount wheel locks interfere less with your hand’s movements but may be harder for some people to engage and disengage. Swing-away wheel locks (also known as scissor wheel locks) may be desirable since you can avoid hitting your thumbs on them when pushing directly on the tires. Some manufacturers have designed wheel locks that mount under the seat so they do not get in the way of pushing. Remember, locking the wheels, although very effective at stabilizing the chair in the right conditions, will not always keep your wheelchair from sliding if the ground is uneven, smooth, wet, or sloped.
You will have to adjust the mounting of your wheel locks after you change the rear wheel position, size, or type of tire so they will work effectively. If you use air-filled tires, the function of the wheel lock will change with the tire pressure. As your tire loses air, the wheel lock may slip. Check your owner’s manual and follow the manufacturer’s instructions to determine how far the wheel locks should penetrate into the tire when they are in the locked position.
Wheel locks are not running brakes that can be applied while you are moving to slow down the speed of your roll. However dynamic wheel locks are available for manual wheelchairs that can be used while traveling downhill. This type of brake serves as both a wheel lock and a dynamic wheel lock.
Front caster wheels
The two small wheels at the front of your wheelchair are called the caster wheels or casters. Caster wheels can swivel or pivot in all directions and improve your wheelchair’s maneuverability. Caster stem housings connect the caster wheels to your wheelchair frame.
Many different types of caster wheels with a range of performance features are available. Small, hard wheels (like rollerblade wheels) can improve maneuverability on hard, flat surfaces but tend to catch in the cracks and crevices of rough surfaces. Larger pneumatic caster wheels are less likely to catch in crevices or on obstacles and handle better over rough terrain but are harder to pivot on almost all surfaces.
Solid rubber or plastic caster wheels usually give a rougher ride than pneumatic caster wheels because they have little shock-absorbing ability. Some users do not like the vibration that occurs using solid rubber caster or plastic caster wheels.
Semi-pneumatic or pneumatic caster wheels give a smoother ride than solid caster wheels and roll over all sorts of obstacles outdoors; however, pneumatic caster wheels have more rolling resistance on hard flat surfaces and can go flat.
The preference for arm supports (often called armrests) varies. Many wheelchair users feel they cannot live without arm supports. Other users do not want arm supports at all. Your personal preference, level of function, and balance will determine whether you want or need arm supports and will impact the type of arm support that will work best for you. Arm supports can provide additional support if you have limited trunk balance and can act as side-to-side stability anchors when you reach sideways. However, many manual wheelchair users do not use arm supports because they may get in the way during propulsion, weight shifts and transfers. They also add to the overall weight of your wheelchair making it somewhat more cumbersome to manage. Transfers in and out of your wheelchair and weight shifts may require more strength and balance without arm supports. If you choose to use arm supports, make sure the style, placement, and height does not interfere with propelling your wheelchair. Your arm supports should be used for resting and should allow you to place your elbows slightly forward of your shoulders when resting your arms.
Verify Correct Seating Dimensions
Your wheelchair seat should be as narrow as possible without touching your hipbones or thigh bones. If the seat is too narrow, it could cause a pressure ulcer. If the seat is too wide, you might have difficulty propelling your chair and getting through doorways. A wide chair might also cause you to lean to the side when you sit or propel, which could lead to the development of a spinal deformity like scoliosis.
There should be about half an inch of space on either side of your hips. The space gives you a little room to move and tuck in your clothing. Seat width affects the overall width of your wheelchair.
The right seat depth is essential for providing the right amount of support under your thighs. If the seat is too shallow, you will experience more pressure on your sitting area, and you could develop pressure ulcers. If the seat is too deep, you will be unable to move all the way against the back of the chair and you will end up slouching backward. A seat that is too deep could interfere with circulation to your legs and cause pressure ulcers behind your knees.
The correct seat depth typically permits about one inch of space between the front edge of the cushion and the back of your knees. The distance needed may be larger if you regularly use your hands to lift your legs, or if you propel your wheelchair with your legs and feet.
If the seat upholstery or seat is too long:
- Talk to a seating specialist about shortening the upholstery or the solid seat beneath your seat cushion.
If the seat cushion is too long:
- Get a shorter cushion or if possible, modify the rear corners of the cushion so it fits farther back on the seat support surface of your wheelchair.
- Move your back support further forward or get a thicker back support, which will move you forward in your seat and shorten the overall seat depth. Remember that this might also change your position in relation to the handrims, so you might have to make other adjustments too.
- Another option is to move the seat cushion back. Sometimes the cushion will even slide under the back support. Make sure your buttocks are still positioned correctly on the cushion.
If the seat is too short:
- Move the back support back if you can. This will allow you to move farther back in your wheelchair, lengthening the seat depth and making room for a longer seat cushion. Remember that this might change your position in relation to your handrims so you may need to make other adjustments when you change the position of the back support.
- Use a longer seat cushion supported over the front edge of the seat upholstery by a firm board or sheet of stiff plastic.
If the seat cushion is too short:
- Get a longer cushion.
When determining the dimensions for a new wheelchair, refer to A guide to Wheelchair Selection (Axelson, Minkel & Chesney, 2006) for guidance. If you already have a wheelchair that has a suitable seat width and depth, adjustments can be made to the chair to make it a better fit. Below is a prioritized list of adjustments that should be considered.
The seat cushion that you need to sit on has to be considered first, before all of the other adjustments on your wheelchair can be considered. Every wheelchair user that is sitting in a wheelchair for extended periods of time is going to want to sit on some type of seat cushion even if the cushion is just a simple 1 or 2 inch foam cushion. For wheelchair users without sensation or with difficulty moving, a pressure relieving cushion is going to be an important consideration. Generally the more pressure relief the taller the cushion is going to be but this does not necessarily mean that your sitting bones are going to be higher off the sling seating. When making measurements for a wheelchair, it is typically best to make all of the measurements while sitting on the seat cushion that will be used in the wheelchair. Some users like to sit on different cushions depending on what they are doing. If a sport chair is being used with one type of seat cushion and an everyday wheelchair is being used with a different seat cushion for everything else, each wheelchair will need to be set up and adjusted while sitting on the specific seat cushion that will be used for the specific wheelchair. Some users have two different types of cushions that they sit on that are different heights for the same wheelchair. This can be accommodated by using an insert beneath the lower height seat cushion so that the height of the seat cushion is the same as the higher seat cushion.
Adjusting the seat angle
Moving the rear axle mounting location up will lower the rear of your wheelchair frame which causes the chair to tip back and lowers the seat height. Then the caster stem housings will need to be adjusted to a vertical position (perpendicular to the ground) so that the chair will roll correctly. This adjustment is possible with most higher end “rehab” wheelchair models. Occasionally there is a vertical adjustment for the caster stem housings to lower the front of your wheelchair frame as well. In other cases it is possible to move the caster wheel upward in the front caster forks. Another possible change is to use a shorter front caster fork or a shorter caster stem bolt. Using a smaller diameter front caster wheel is another way to lower the front end of your wheelchair. Moving the rear axle down will raise your wheelchair frame in the rear, which will raise the seat height in the rear but will cause the seat support surface to tilt forward.
After adjusting the vertical position of the rear wheels, you may also have to change the height and/or angle of the caster wheels to maintain your desired seat plane angle. Make sure the caster stem housings are vertical (perpendicular to the ground) so that the chair will roll correctly.
If you adjust your vertical position in your wheelchair via the seat rather than the wheel axle, you will not have to readjust the caster stem housings when you change the seat and back position. This adjustment is only possible on some wheelchair models.
Adjusting the back support height
The back support height should be comfortable and provide good lower back support. A lower back support lets you move your arms and upper body more. If needed, a higher back support provides more upper-body support.
The back posts or push handles should not interfere with arm movements while you are wheeling. They may be adjustable in height. Check with your supplier or the user manual for further information. Many wheelchair users do not like push handles since they get in the way and they seem to encourage well-meaning people to push the wheelchair without asking. Fold-down, push handles are available on some wheelchairs. They can be put in place when you need them and folded down when they are not needed. Back supports are also available without push handles but if you sometimes need help from someone else to propel or maneuver your chair, push handles make it much easier for the assistant.
Adjusting the back support angle
Your back support angle should provide a comfortable sitting posture while you are upright in the wheelchair. The back support angle should not cause you to slump, curl your shoulders, hold your head forward for balance, or cause you to slide out of your seat.
The angle formed by the seat and the back support is called the seat-to-back angle. The seat-to-back angle greater than 90° is an open angle, while an angle smaller (tighter) than 90° is a closed angle. An open angle lets you use gravity to help balance your trunk. People who cannot flex well at the hips often use an open seat-to-back support angle. However, an open angle may cause people to slide out of their chairs. The open angle may also change your position in relation to the handrims making your wheelchair harder to propel.
A closed angle cradles the body in the curve of the seat, holding you in place and often reducing leg spasticity. Some people combine this with a higher rear axle position which lowers the back of the seat creating even more of a cradle. This is sometimes called seat dumping. People with high spinal cord injuries and very poor trunk balance prefer a more closed seat-to-back angle for enhanced trunk stability. Not all wheelchair users can tolerate a more closed (or tighter) seat-to-back angle which requires more hip flexion. Be sure you have sufficient range of motion at the hips if you are considering closing your seat-to-back angle. This can be helpful to people with limited fore aft trunk movement and stability as it provides the needed support by changing the direction of the force of gravity while increasing maneuverability by keeping the shoulders in a better position to push the wheels.
Adjusting the seat surface height, leg support, and foot clearance
Your seat height and leg support length and angle are interdependent and must be determined together. Your seat height determines the vertical space available for your legs thereby determining the degree of leg angle necessary to accommodate the length of your legs. Inversely, your leg angle can determine how high your seat must be to accommodate your leg length, leg angle, and your feet on the foot supports. It is important that the seat is high enough for your foot supports to clear obstacles and low enough for your knees to fit under tables. According to the Americans with Disabilities Act Accessibility Guidelines, standard tables or counters should have knee clearance spaces at least 27 inches high.
Your leg angle will impact your comfort and the length of your footprint. A larger angle from the bottom of the seat to the back of the calves will allow greater foot support clearance and/or a lower seat height. This means that your feet will be out further in front of you which makes your overall length longer and might make maneuvering in small spaces more difficult. Some people will choose to have their legs angled under the chair. This reduces the length of your footprint and provides a “sportier” look, but will decrease your stability and may impact the blood circulation in your legs and feet.
There are factors that can be altered to help accommodate the necessary seat height, leg angle, and ground clearance. These factors include the vertical rear wheel height, the caster height, the axel position, and your seat cushion thickness. Larger rear wheels and front casters will raise the chair higher off the ground. Smaller rear wheels and front casters will lower the chair. Lowering the rear wheel axle position will raise the rear of your wheelchair higher off the ground while raising the axle position will bring the rear of the wheelchair closer to the ground. You can increase the seat cushion thickness to raise the seat height by adding padding or a solid insert under the cushion. You can decrease cushion thickness to lower the seat height.
Making changes to your axel position and wheel height will change your position in relation to the handrims which may make it harder or easier to propel your wheelchair. Lowering the seat height will make it easier to reach the handrims, which might provide more power when you propel your wheelchair. If you are too low in relation to the handrims but need the lower seat height, you can replace the rear wheels with smaller diameter ones. You can also use smaller rear wheels if you want the seat height to be even lower.
There are other ways to raise your wheelchair seat height. The height of some wheelchair seat support surfaces are adjustable and can be raised to accommodate leg length and leg clearance. Seat supports with extensions can also be installed to raise the seat higher.
If your legs are long, you might have to compromise between sitting comfort and leg clearance. It is more important for you to fit properly and comfortably in your wheelchair than to be able to roll under all tables. If you need more clearance under a table at home or work you could raise the table up higher. You can place a layer of plywood beneath the base or between the tabletop and the base. If the table has individual legs you can make blocks of wood with shallow holes on the tops of them to keep the blocks positioned under the table legs. Make sure the table is secure and will not slide off whatever you use to raise the table up. A higher seat is also useful for people who have difficulty standing up from or sitting down onto low surfaces.
After determining your seat height and leg angle, adjust the positioning of your foot supports. You should have your cushion, back support, and other positioning aids in place when adjusting your foot supports. Don’t forget to put your normal shoes on; sole height affects your leg positioning. Make sure you are seated upright against the back of the chair. When adjusting the foot supports:
- Make sure you have clearance of two inches underneath the foot plates so your foot plates do not get caught on small obstacles in the roadway.
- Also have clearance for your knees under desks and tables.
- Some experienced users ride with less ground clearance so that if the wheelchair tips forward on a level surface, the foot supports themselves will prevent the chair from tipping over forward.
If you do not have enough clearance, you might need to readjust the seat plane angle and height. When your feet are supported at the correct height by your foot supports, your thighs should rest in a balanced manner on your cushion. Foot supports that are too high can lead to little or no weight under your thighs (especially near your knees) and cause excessive weight under your sitting bones, the ischial tuberosities, which could lead to pressure sore development. You might need to compromise on your knee height and how easily you can roll under tables without hitting, in order to get the best leg support.
Some wheelchairs can be ordered with a steeper footrest angle at the front, allowing your legs to be tucked further under the chair versus having your feet out in front of your wheelchair. This shortens the overall length and may make it easier for you to maneuver your wheelchair in tight spaces.
Swing-away foot supports can be moved out of the way or removed. When you take your feet off the foot supports and swing them out of the way or remove them, you should be able to get closer to obstacles but, your feet will be dangling. If they reach the ground, you may still get the support you need to hold your balance while sitting close to a desk or table, but if you need your feet and legs to be well supported in order to have trunk balance, removing your feet from the foot supports may cause you to lose your balance. Removing or swinging away the foot supports may be necessary for you to perform safe transfers to and from your wheelchair.
Adjusting rear wheel camber
Camber is the off-vertical tilt of the rear wheels. It widens the distance between the bottoms of the propulsion wheels and narrows the distance between the tops of the wheels. Wheel camber increases side-to-side and forward stability. Camber also increases your wheelchair’s overall width, which may make it difficult to roll through narrow doorways. Increasing wheel camber may also make your seat width narrower so make sure your hips are not rubbing or squeezed. Follow the owner’s manual instructions to adjust wheel camber.
When adjusting the camber of your rear wheels, be careful not to set them toed in or out. Toed out means the front edge of the rear wheels are pointed outward away from your feet. Toed in means the front edge of your rear wheels are pointed inward, toward each other and your feet. Setting the wheels to toe in or toe out will make your wheelchair more difficult to propel and causes the tires to wear unevenly.
Adjusting the rear wheel axle horizontally
Next, set the horizontal position of the rear wheel to meet your stability requirements. Surprisingly, a completely stable wheelchair is not always desirable. As with many vehicles, including cars, bicycles, and motorcycles, a wheelchair that is less stable in the rearward direction is also easier to maneuver. Your chair will provide the best performance if you position the rear axle as far forward as you can while maintaining your balance comfortably during all types of activities. Rear wheels that are set too far forward may interfere with the movement of the front caster wheels while making the wheelbase extremely short and your wheelchair unstable. You will tip over backwards too easily if you set the rear axle too far forward for your ability and the environments where you use your wheelchair.
Moving the rear axle in the fore/aft direction (forward or backward) changes the location of the center of gravity with respect to the rear wheels. The more forward the axle is positioned, the less weight will be over the front caster wheels. This will make the chair easier to tip back and pop into a wheelie, but will also make it more difficult to push up a hill without tipping backward. It is much easier to maneuver over obstacles and turn around in small spaces in a wheelie (Section 1.9 has more information about wheelies.)
If you know how to hold a “wheelie” – balance the chair on the rear wheels only – you may want to start the rear wheel adjustment about 2” forward of the back posts. Test the stability of the chair. With either someone behind you to “spot”, or by having an anti-tipping device on the chair, give the chair a push forward, are you comfortable with the response? If the chair tips back to far, or too fast; consider moving the wheels back slightly. If you are comfortable with the chair’s response, you may want to move the wheel further forward to find the spot where you are uncomfortable, then move it back slightly. True wheelie performance begins at the edge of your comfort zone.
Test drive each new setup by going up a standard ramp with a spotter to make sure the position of the rear wheel axle will not cause your wheelchair to tip over backward.
Adjusting the caster stem housing
Your caster stem housings should be perpendicular to the ground. If they are not, your front caster wheels may become afflicted with “shopping cart syndrome” and flutter when you propel your chair. This may also make it difficult to turn your wheelchair or change direction. Use a book or carpenter’s angle to make sure the caster stem housing is perpendicular to the ground. Consult your owner’s manual for detailed instructions on how to adjust the caster stem housing angle.
The optimal sitting position for most wheelchair users is with a seat-to-back support angle somewhere between 90-100° and a knee angle in the range of 90-120° of extension. Some wheelchair users like to sit with their feet tucked under their wheelchair creating a tighter knee angle of 70-80°. This may shorten the overall length of your wheelchair and make it easier to maneuver. Shown: 90° seat-to-back support angle and 120° of knee extension.