Strongback Mobility Glossary

A plain-English glossary of the wheelchair terms that actually decide whether a chair fits, travels and lasts. Every entry answers one question, in one place, so you can compare chairs from any brand on the same basis. Where a term applies differently to a Strongback model, that is stated under the definition.

Last reviewed September 2026 by Christian Grothe, CEO, Strongback Mobility. Specifications quoted here are from the Strongback Master Data Guide, SBM-ALL-SPEC-001 v10.9.

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Posture Support

What is posture support in a wheelchair?

Posture support is everything in a wheelchair that holds the body upright: the contour of the backrest, the seat angle, and a seat width that keeps the trunk centered. Lumbar support is the core, but the three work together. Get one wrong and the others stop working.

A flat sling backrest offers nothing for the lumbar curve, so the pelvis rotates back and the spine rounds. Over hours this produces lower back ache and increases shear force on pressure-sensitive areas. Strongback wheelchairs build the lumbar contour into the frame and let the user adjust it to their own back.

Sacral Sitting (Posterior Pelvic Tilt)

What is sacral sitting and why does it happen in a wheelchair?

Sacral sitting is what happens when the pelvis rotates backwards and the user ends up resting on the tailbone rather than sitting on the sitting bones. The lower back rounds outward instead of curving inward.

It is the default posture in a wheelchair with a flat sling backrest, because there is nothing holding the lumbar curve. The user starts upright, gradually slides forward, and after an hour is sitting on their sacrum with their spine in a C-shape.

Common consequences of sustained sacral sitting:

  • Lower back pain and fatigue from holding a rounded spine
  • Load concentrated on the tailbone rather than the sitting bones, with shear force building in the tissue
  • Compressed breathing and digestion from spinal flexion
  • Forward head position that strains the neck and shoulder girdle

It is also self-reinforcing: a rounded spine makes it harder to push back up into upright posture.

Preventing sacral sitting requires two things: the backrest to hold the lumbar curve, and the seat to keep the pelvis in place. That is what seat angle and frame-integrated lumbar support are both for.

Transport Chair

What is a transport chair and how is it different from a wheelchair?

A transport chair is a manual wheelchair with small rear wheels and no hand rims, designed to be pushed by another person. The user cannot propel it themselves, because there is nothing to grip and turn.

Rear wheels on a transport chair are typically 8 to 12 inches, against the 22 to 24 inches of a self-propelled wheelchair. Removing the large drive wheels makes the chair lighter, narrower and more compact when folded. The trade-off is that the user depends on a caregiver to move.

The terms are often blurred in retail listings, where "transport wheelchair" is used for both types. The test is simple: if there is a metal ring on the outside of the rear wheel, the chair is self-propelled. If there is not, it is a transport chair.

Strongback Mobility makes both. The Strongback Excursion line is attendant-propelled: Excursion M and Excursion L, with 12-inch rear wheels, no hand rims and attendant brakes as standard. The self-propelled models are the Strongback Comfort line (Comfort S, Comfort M and Comfort L), the Strongback Comfort Flip, the Strongback Heavy Duty and the Strongback ErgoSteel, all with hand rims and 22 to 24-inch rear wheels.

Self-Propelled Wheelchair

What is a self-propelled wheelchair?

A self-propelled wheelchair has large rear wheels with hand rims the user grips and turns to move themselves. Rear wheels are typically 22 to 24 inches.

This is the distinction that separates independence from assistance. A self-propelled chair can be pushed by a caregiver as well, so it covers both modes; a transport chair only covers one. The cost is weight and folded bulk, since the large drive wheels have to go somewhere.

Quick-release wheels reduce that cost: the wheels come off in seconds, and what goes into the car is the frame alone.

Attendant Brakes

What are attendant brakes on a wheelchair?

Attendant brakes are a lever built into each push handle that lets the person pushing the chair apply the parking brake from behind, through an internal cable, without bending down to the wheel.

They are not a separate braking system. The chair's parking brakes are what they operate; the levers simply put that control in the caregiver's hands. On a chair that is being loaded, parked on a slope or held steady during a transfer, that saves the caregiver bending to each wheel in turn.

If what you need is progressive control of a chair already in motion, that is a drum brake rather than an attendant brake. The two are often described interchangeably in product listings and they are different hardware.

Attendant brakes are frequently sold as a paid option or as a separate model variant rather than fitted as standard. Check whether they are included rather than assuming, and check it per model, because the answer often differs between sizes of the same chair.

Strongback option: attendant brakes are standard across the Strongback Excursion line and on the Strongback Comfort M and Comfort L, not a paid add-on.

Hand Rims

What are hand rims and why does their shape matter?

Hand rims are the narrower metal rings mounted outside the rear wheels of a self-propelled wheelchair. The user grips the rim, not the tire, to push and steer.

Standard hand rims are round tubing, which concentrates pressure into a small area of the palm and thumb. Ergonomic hand rims are shaped, flattened or contoured, to spread that load. Over a few hundred pushes a day, the difference shows up in the wrists and thumbs.

The presence of hand rims is the quickest way to tell a wheelchair from a transport chair.

Seat Width

How do I measure seat width and what size should I choose?

Seat width is the horizontal distance between the inside faces of the armrests at seat level, and it is the single most important fit dimension on a wheelchair.

Measure across the widest point of the hips and thighs while seated, then add roughly one inch of clearance on each side. Standard adult wheelchairs come in 16, 18 and 20 inches; bariatric models go to 22 inches and above.

Too narrow presses on the hips and restricts circulation. Too wide is the more common mistake and does more damage than people expect: the arms lose their natural resting position, the shoulders round forward, and the trunk drifts to whichever side has room, which undoes whatever back support the chair provides.

Seat width is a nominal size class rather than a measured value, so compare classes across brands and check the overall width separately before you judge whether a chair fits your home.

For more information, please visit our Sizing Guide.

Quick-Release Wheels

What are quick-release wheels and why do they matter?

Quick-release wheels come off the axle by pressing a button in the hub, without tools. They are refitted the same way.

The point is what a caregiver has to lift. A wheelchair that weighs 27 lb complete might weigh 16 lb once the wheels are off, and the frame folds flatter without them. For anyone loading a chair into a car several times a week, this is usually the difference between manageable and not.

They also matter for air travel, where a chair that is too large fully assembled may still qualify for in-cabin stowage once the wheels come off.

Strongback option: 22-inch and 24-inch rear wheels are quick-release. On the Strongback Excursion the 12-inch rear wheels are fixed rather than quick-release, so its published weight already includes them.

Carry Weight vs. Total Weight

What is the difference between Carry Weight and Total Weight on a wheelchair?

Carry Weight is the folded frame without wheels, footrests and anti-tippers. Total Weight is the frame plus wheels and footrests; anti-tippers are not included. Manufacturers quote both, and the gap between them is often 10 pounds or more.

Neither figure is wrong, but they answer different questions. Total Weight tells you what the chair weighs as it rolls. Carry Weight tells you what you lift into the trunk, because the wheels come off first and go in separately.

Retail listings frequently quote whichever number is lower without saying which one it is. Always check the basis. A bare number means nothing on its own. For example, the Strongback Comfort S has a Carry Weight of 15 lb and a Total Weight of 23.6 lb: the same chair, two different questions.

Anti-Tippers

What are anti-tippers and when should they be removed?

Anti-tippers are short bars extending backwards from the rear axle with small wheels on the ends. If the chair tips back beyond a set angle, they contact the ground and stop it going over.

They are standard on most wheelchairs and removable by hand. Experienced users sometimes take them off, because tipping the chair back deliberately, to clear a curb, is a technique anti-tippers prevent.

Practical guidance, not a clinical standard: keep them on until you can consistently execute a controlled back-tilt, and treat that as a skill to be taught rather than discovered. New users should leave them on.

Anti-tippers are excluded from every published weight figure, including Total Weight, because they are an optional fitment.

Center of Gravity

How does center of gravity affect how a wheelchair handles?

Center of gravity is where the combined weight of chair and user sits relative to the rear axle, and it determines how the chair behaves.

Set further forward, the chair is stable and hard to tip backwards, but heavier to push and slower to turn. Set further back, less weight rests on the front castors, so the chair turns quickly and takes less effort per push, and tips more easily.

Some wheelchairs have a multi-position rear axle so this can be adjusted as the user gains experience. Chairs built for higher weight capacities need the geometry designed for that load rather than adapted from a standard frame.

Wheel Locks

What are wheel locks and how do they differ from brakes?

Wheel locks, also called parking brakes, are levers that press a bar against the tire to hold a stationary chair in place. They are standard on essentially every wheelchair and are what you engage before a transfer.

They are not speed control. A wheel lock is not designed to slow a moving chair and should not be used to do so. Progressive control of a chair in motion is what a drum brake does. Confusing the two is common in product listings.

Strongback option: every Strongback model carries a push-to-lock parking brake on each rear wheel as standard, whatever else the chair is fitted with.

Swing-Away Footrests

What are swing-away footrests and when do I need them?

Swing-away footrests pivot outward to the side and lift off the frame entirely. This clears the space in front of the seat for standing up or transferring across.

Fixed footrests force the user to step over or around them. For anyone who still stands, or who transfers sideways to a bed or car seat, swing-away footrests are the difference between a straightforward move and an awkward one. They also remove several pounds before the chair goes into a car.

Castors

What are castors and what size matters?

Castors are the small front wheels that swivel and steer the chair. Typical sizes run from 5 to 8 inches.

Larger castors roll over thresholds, gravel and pavement joints more easily but need more space to turn. Smaller castors turn tighter, which matters in narrow hallways and bathrooms, but catch on obstacles a larger wheel would clear. Chairs built for higher weight capacities generally use larger castors.

Strongback option: 6-inch castors on the Strongback Comfort line, the Comfort Flip and the Excursion; 7-inch on the Strongback Heavy Duty; 8-inch on the Strongback ErgoSteel.

Desktop-Length Armrests

What are desktop-length armrests and why would I want them?

Desktop-length armrests are shortened at the front so the chair can pull up close to a table or desk, with the armrest passing underneath.

Full-length armrests run the whole depth of the seat and support the forearm better, but they stop against the table edge and leave the user sitting a foot back from it. Desktop-length is the usual choice for anyone who eats at a table, works at a desk or uses a kitchen counter.

Flip-Back Armrests

What are flip-back armrests and who needs them?

Flip-back armrests hinge upward and backward, clearing the side of the seat completely.

This matters for side transfers, sliding across to a bed, a car seat, a commode or a shower bench rather than standing up. With a fixed armrest in the way, the user has to lift their body over it. With the armrest flipped back, there is a clear path across, which is also what a slide board transfer requires.

In the Strongback range this is the Strongback Comfort Flip.

Seat Depth

What is seat depth and how do I measure it?

Seat depth is the horizontal distance from the front edge of the seat to the front face of the backrest, and it decides how the thighs are supported.

Measure from the back of the hips to the back of the knee while seated, then subtract about two inches. Too deep and the front edge presses into the back of the knees, restricting circulation and pushing the user to slide forward. Too shallow and the thighs hang unsupported, putting the whole load onto the buttocks.

Sliding forward to escape a seat that is too deep is one of the most common causes of slumped posture in a wheelchair: the pelvis rotates back and the spine rounds, regardless of how good the backrest is. See sacral sitting.

For more information, please visit our Sizing Guide.

Seat Height

Why does seat height matter and what is the right height?

Seat height is the distance from the floor to the top of the seat at the front edge, and it determines whether the feet reach the ground and how transfers work.

For users who can still stand or walk short distances, the feet need to reach the floor with the knees at roughly a right angle. A seat that is too high leaves the feet dangling and the user unable to push up out of the chair. Too low and standing up requires more strength from the legs than many users have.

Seat height also has to be matched to whatever the user transfers to: a bed, a car seat, a toilet. A level transfer is far easier than an uphill one. Standard adult seat height is around 19 to 20 inches; chairs built for smaller adults sit lower.

To find the right height, measure from the back of the heel to the back of the knee while seated. If the user propels with their feet, use that measurement as the seat height, so the feet reach the ground. If the user propels with their arms, add 2 inches to allow footrest clearance.

For more information, please visit our Sizing Guide.

Backrest Height

What does backrest height do and how does it affect propulsion?

Backrest height is measured from the seat to the top of the backrest, and it trades trunk support against shoulder freedom.

A higher backrest supports more of the spine and suits users with limited trunk control. A lower backrest frees the shoulder blades, which matters for anyone self-propelling: pushing requires the shoulders to move backwards, and a backrest that reaches the shoulder blades gets in the way.

Most self-propelled wheelchairs use a backrest that stops just below the shoulder blades. Where the lumbar support sits within that height matters more than the height itself.

Seat Angle (Seat Dump)

What is seat angle and how much does it matter?

Seat angle, sometimes called seat dump, is the tilt of the seat from front to back, with the rear sitting lower than the front. It is measured in degrees.

A few degrees of angle settles the pelvis into the back of the seat and stops the user sliding forward. It also makes the chair harder to fall out of. Too much angle makes standing up and transferring difficult, and puts more pressure on the tailbone.

How much angle is right depends on the user. Someone who transfers by standing wants less; someone who slides forward over a long day wants more. The figure varies between chairs and is not always published, so ask for it rather than assuming.

Strongback option: seat angle is 12 degrees on every model in the Strongback range.

Drum Brakes

What are drum brakes on a wheelchair and why are they better than wheel locks?

Drum brakes work inside the wheel hub, pressing shoes outward against a drum, in the same way as a car's rear brakes. On a wheelchair they are operated by the attendant from the push handles.

They differ from lever-type wheel locks in what they can do. A drum brake slows a moving chair progressively, holds it on a slope, and does not lose effectiveness when the tire is wet or worn. A wheel lock only holds a stationary chair.

Two-way locking and running drum brakes do both jobs: they park the chair and control speed in motion. On heavier chairs, where the combined weight of chair and user is greater, this is a meaningful safety difference on any incline, and it is frequently a paid option rather than standard equipment.

Strongback option: in the US range, drum brakes are standard on the Strongback Heavy Duty. No other Strongback model sold in the US is fitted with them.

Overall Width

Why does overall width matter and how do I measure the right fit?

Overall width is the widest point of the chair, usually across the rear wheel hubs or the push handles. It is not the same as seat width.

This is the number that decides whether the chair passes through doorways, and it is routinely confused with seat width in product listings. A chair with an 18-inch seat is typically 24 to 26 inches wide overall.

Interior doorways in US homes are commonly 32 inches wide, and the clear opening is smaller than the nominal size once the door and frame are accounted for. Bathroom doors are usually the narrowest in the house.

Measurement method: measure the narrowest doorway with the door open at 90 degrees, then subtract 1 inch for hand clearance. Compare against the chair's spec sheet Overall Width, not the seat width.

Tire Types: Solid vs. Pneumatic

Should I choose solid or pneumatic (air-filled) tires?

Wheelchair tires are either solid, made of polyurethane or solid rubber, or pneumatic, meaning air-filled.

Solid tires never puncture and never need inflating, which is why most transport chairs and many folding wheelchairs use them. The cost is ride quality: they transmit more of every bump straight through the frame to the user.

Pneumatic tires absorb vibration and grip better on loose ground, which matters for outdoor use and for users with pain or pressure sensitivity. They need checking and inflating, and they puncture.

Foam-filled tires sit between the two: they cannot puncture, but they ride harder than air and add weight.

Strongback option: every Strongback model runs solid tires. There is no pneumatic option in the range.

Airline Travel and Gate Check

What is gate check and how do I travel with a wheelchair on an airplane?

Gate check is the process of handing a wheelchair over at the aircraft door rather than at the ticket desk, so the user keeps it through the terminal and gets it back at the door on arrival.

US rules for air travel sit in the Air Carrier Access Act and its regulation, 14 CFR Part 382. Two parts of it matter most to a manual wheelchair user:

  • The chair comes into the cabin, and it is not carry-on baggage. Carriers must permit passengers with a disability to bring manual wheelchairs, including folding and collapsible ones, into the cabin, subject to the usual safety and security rules, and they must not count an assistive device toward a carry-on baggage limit (14 CFR 382.121).
  • Larger aircraft must hold priority space for one chair. On any aircraft with 100 or more passenger seats, the carrier must provide priority stowage space, separate from the overhead bins and under-seat space, large enough for at least one typical adult-sized folding manual wheelchair measuring 13 by 36 by 42 inches or less, without the wheels being removed. The carrier must also offer pre-boarding to a passenger stowing a wheelchair in the cabin (14 CFR 382.67).

Practical points: remove and carry footrests, cushions and anything detachable, because loose parts go missing. Label the chair. Request gate check when booking, not at the airport. Damage in transit is common, so photograph the chair before handing it over. If in-cabin stowage is the goal, check your chair's folded dimensions against the 13 by 36 by 42 inch figure before you fly.

Heavy Duty / Bariatric

What is the difference between "heavy duty" and "bariatric" wheelchairs?

Heavy duty and bariatric both describe wheelchairs built for higher weight capacities, and the terms are used interchangeably in retail listings. Heavy duty is the more precise of the two. Bariatric has no fixed threshold: it usually signals both raised capacity and a wider seat, but what stands behind it varies by manufacturer.

When comparing chairs in this category, read the rated capacity and the seat width rather than the label. Also check overall width: many chairs rated above 300 pounds are too wide to pass through a standard interior doorway, which decides whether the chair works throughout a home or only outside it.

Strongback option: the Strongback Heavy Duty is rated to 375 lb and is home-compatible at a 31-inch overall width, so it passes through a standard 32-inch home doorway. It is self-propelled, with 24-inch rear wheels and drum brakes as standard.

Folding Wheelchair

Folding frame or rigid frame: which should I choose?

Manual wheelchairs come in two frame types: folding and rigid.

A folding wheelchair uses a cross-brace, usually described as an X-frame, which scissors together so the two side frames meet and the chair folds in half across its width. This is by far the most common manual wheelchair design, and it is what almost every transport chair and standard wheelchair uses. The wheels can usually be removed as well.

A rigid wheelchair does not fold across its width. Instead the backrest folds down and the wheels come off, leaving a flat package. Rigid frames have fewer moving parts and lose less of the push through the frame, which is why they are the usual choice for active full-time users.

Neither is automatically better. Folding frames pack into tight car footwells and are what most funding routes supply. Rigid frames are typically lighter and more efficient to push, but their capacity is usually capped around 350 lb, so users above that will be looking at a heavy duty folding chair. Quick-release wheels reduce the lift weight either way.

Ergonomic Wheelchair

What does "ergonomic" actually mean for a wheelchair and what features matter?

Ergonomic in a wheelchair context means the chair is designed to support the natural curves and load distribution of the spine and pelvis, reducing fatigue and pain during extended use.

Specific ergonomic features include: frame-integrated lumbar support rather than a removable add-on, adjustable posture support, a seat angle that holds the pelvis stable, contoured hand rims rather than round tubing, and armrest positioning that does not force the shoulder girdle forward.

The word is often used as a marketing term without any of these features behind it. The useful test is whether the support is built into the frame or added on top of it, whether it adjusts to the individual, and whether the manufacturer will give you the geometry when you ask.

By that test, the patented Strongback backrest builds the lumbar contour into the frame rather than adding it on top, and its tension is set by the user rather than fixed to an average. That holds across the range, on every Strongback model, the ErgoSteel included.

Lumbar Support

What is lumbar support and what does it do for the lower back?

Lumbar support is the part of a backrest that fills the natural inward curve of the lower spine and holds the pelvis neutral. It is the single component that does most of the work in posture support.

Without it, the pelvis rotates backwards and the spine collapses into a C-shape. With it, the pelvis stays vertically stacked, which is the position the body is built to hold weight in.

For users with existing back pain, adjustability matters more than fixed geometry, because the depth of the lumbar curve varies considerably between people. A backrest set for someone else's spine supports the wrong part of yours. On every Strongback model the backrest panel is held by hook-and-loop straps, so the tension can be set at any height and to any firmness.

Equally important: a chair that is too narrow or too wide creates compensatory trunk lean, which negates the benefit of any lumbar support. Proper seat width is not optional.

Buying in Person vs. Buying Online

Where should I buy a wheelchair and what is the difference?

The real difference is how much hands-on support comes with the chair. A wheelchair is a fitted product, so the question worth asking is how much help you want with sizing, setup and service over the years you will own it.

  • An in-person store, whether it calls itself a DME supplier, a medical-equipment dealer or a mobility retailer: the one route where you can sit in the chair before you decide and have it set up for you on the spot, with the seat, the footrests and the rear axle adjusted to you rather than to an average. Many stores also service and repair what they sell, which matters over the life of a chair. Ask before you buy, because that varies from store to store.
  • Direct from the manufacturer (for example, Strongback Mobility): full spec transparency, direct access to product documentation, and someone who knows the whole product line when you have a question about fit or configuration.
  • Online: the right route if you already know your measurements, need little setup help, or have no store within reach.

Recommended approach: if there is a store near you, sit in the chair and have it fitted before you decide. A ten-minute fit check catches what a spec table cannot, from a seat width that is an inch too wide to footrests set for someone else's legs. If you are buying online, work through the Sizing Guide first, and call us on 757-349-7790 if any measurement is borderline.

To find somewhere to sit in a Strongback chair, use our retailer finder.

Still not sure which chair fits?

Work through the measurements in the Sizing Guide, read the frequently asked questions, or compare the range in Strongback wheelchairs. If you would rather talk it through, call us on 757-349-7790.