This guide summarizes the components and ergonomic benefits of swivel executive, managerial and task chairs.
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People who are at their desk for extended periods of time often experience back or neck pain after sitting for long periods of time. Ergonomic office chairs are are scientifically designed for proper alignment of the human body to prevent backaches and muscle strain, thus increasing comfort and productivity.
A. Headrest
Some chairs have a headrest or offer it as an option. The benefit of a headrest is that it allows you to take strain off of your neck while reading or reclining.
Some headrests are separate and adjustable, while others are built into the back of a high-back chair. The Humanscale Freedom automatically moves up to support the head when reclining, then moves back when the chair is upright.
B. Seat Back
Seat backs may be low, mid or high-back. Executive chairs are often thought or as having high backs, while task chairs are usually mid-back or low-back. However, this is not always true. Some ergonomic chairs have high backs and are referred to as task chairs. Adding to the confusion, some mid-back chairs are called managerial or manager's chairs. In most cases, itis better to decide which back height fits your needs, rather than focusing on definitions such as executive, managerial or task chairs.
There are a wide variety of configurations, ranging from traditional cushioned backs and mesh backs, as well as unusually shaped ergonomic backs.
Seat backs vary in how they are joined to the seat, affecting height and ability to recline. Variations include:
Seat Back Height
Some seat backs are fixed in height, while others allow height to be adjusted up or down to fit the user. This height adjustment allows more comfortable positioning of lumbar and shoulder support.
Recline and Backrest Angle - The back may or may not recline. Adjusting the angle of recline transfers some upper-body weight to the backrest, and lightens the load on the body’s lower spine. Changing the angle between the torso and thighs can also result in less pressure on the discs by curving the lower back inward.
- Some chair backs are fixed to the seat pan without any movement.
- Other chair backs simply flex backwards from the seat pan a limited amount without adjustment controls, using springs or support materials which flex.
- In some chairs that recline, the seat and back recline together relative to the floor. This transfers some of the upper-body weight to the backrest. The pivot point can be at the top of the seat post, putting slight pressure on the back of thighs or knees. If the pivot point is forward of the post, the pressure is reduced further. See HON Pneumatic Task Chair below.
- Asynchronous Control means that the back is allowed to recline, while the seat remains stationary.
- Asynchronous control tilt lock levers allow you to recline or prevent reclining.
- Some asynchronous control backs are engineered to sense the desired recline position, and may or may not have a tilt lock.
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C. Lumbar Support
Lumbar support in chairs range widely in amount of support and adjustability, having:
- no lumbar support,
- support in a fixed position,
- lumbar support that is adjusted up or down by raising or lowering the seat back,
- lumbar support that moves up or down the seat back,
- ability to adjust lumbar pressure against the spine,
- lumbar support may consist of foam in the chair back, a moving pad or brace, or stretched mesh.
The spine can maintain a natural curvature without lower back support from the seatback. However, fo most people who sit for a long period, this pushes the lower back so that the natural inward curve goes in the outward toward the chair. This strains the structures in the lower back and people tend to slouch forward. A good lumbar back support should be comfortably flush against the small of the back, but not pushing excessively forward.
In the case of a chair that is to be used every day by the same person, the user may find a chair with comfortable fixed lumbar support without needing adjustment controls. Alternatively, another person may prefer a high degree of adjustability, or a chair used by multiple people may need adjustable lumbar support for individual comfort.
D. Seat Pan
Chair seat pan depth can be fixed, the seat pan can slide forward or backward, or the backrest can be moved in or out relative to the seat pan. Small people need a shorter seat pan to allow them to use the back rest and prevent pressure on the back of the knees. Tall people feel more stable and comfortable with deeper seat pans.
Seat pan width, depth and front edge are important considerations. Most ergonomic experts believe that the seat pan should be at least one inch wider than your hips and thighs on either side. The back of the knees should not touch the front edge of the chair, and the front edge of the chair should not restrict circulation by pressing on the back of the thighs. Some seats have waterfall front edges to prevent this. (example images)
Seat Pan Angle – Some chairs allow forward tilt of the seat pan front. This widens the angle between the trunk and thighs, curving the lower back inward and reducing pressure on the discs.
Products With Adjustable Seat Depth / Seat Glide
E. Cushion & Upholstery
Seat Cushion
There are a variety of materials used in seat cushions, including:
Foam – Chairs have various grades of foam, including low or high density foam, and memory foam. Chairs intended for constant use, such as “24-hour” chairs have very durable foam and upholstry. The foam in some mass-market chairs feels good at first, but breaks down over time. Unfortunately, it is difficult to identify these chairs.
Gel – The gel moves away from high-pressure areas and fills in gaps in low-pressure areas, thereby distributing body weight and easing pressure under the sitting bones. If you want a gel seat in a chair, either make sure the description specifically says that the model has a gel seat or allows you to order it as an upgrade option.
Mesh – Mesh cushions vary widely. Some mesh cushions have multiple layers, are soft and feel more like a cushion. Other mesh seats are tightly stretched fabric.
F. Upholstery
The most common materials are cloth, mesh, leather and vinyl. All materials have pros and cons:
- Cloth breathes, helping to keep the user cooler, but some stains may be more difficult to clean. It can also trap moisture in the cushion.
- Mesh breaths very well. There are a variety of mesh fabrics, ranging from soft to stiff. Some stiffer mesh fabrics can be abrasive to clothes.
- Leather often feels good and is attractive, but may also be hotter and not breathe as well as cloth or mesh.
- Vinyl is easy to clean, but can be hot and does not breathe.
- There are a variety of synthetic materials now available, as manufacturers focus on keeping the user cool and comfortable.
G. Armrests
While executive and managerial chairs usually have armrests, armrests are sometimes optional for task chairs.
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Ergonomic research strongly emphasizes the benefits of properly adjusted armrests in reducing neck, shoulder and spine injury, as well as improving productivity of people who use computers. Armrests that are too high can elevate the shoulders and put pressure on the elbows and forearms. Armrests that are too low can cause slumping or leaning to one side.
Some armrests are fixed in one position, while others allow adjustment for distance from torso, height or rotation of the pad. The ability to adjust armrest height not only provides proper arm support, it can also allow armrests to move out of the way while typing or when free motion is needed. |
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Courtesy of OSHA
The ability to adjust armrest distance from the torso allows the arms to rest at the user’s side, rather than being splayed outward.
Padded armrests reduce pressure on the elbows and forearms, as compared with rigid armrests. |
H. Control Mechanisms
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The structure that supports and often adjusts the seat and back is called the control mechanism or underseat mechanism. Office chairs range from few to many control levers. All chairs should have the ability to control seat height. Some people prefer extensive adjustment capabilities, while other people do not use them.
A chair may lack control mechanisms because the chair is simple, or because sophisticated engineering has eliminated them. Possible control adjustments include: seat height, seat angle, seat pan position, seat recline tension, back height, back recline, or arm rest adjustments. |
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Example Control Mechanism
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I. Support Post, Base & Casters
Support Post
The support post adjusts seat height using a lever under the seat. Feet should rest comfortably on the floor, without putting pressure on the backs of the thighs, and with the keyboard or desk at the appropriate height. Most chairs that roll have a 360 degree swivel around the seat post and base.
Almost all modern support posts use compressed inert gas in a cylinder, also referred to as pneumatic seat height adjustment. Extended post heights for task and executive chairs generally range from 3.1 to 5.5 inches (80 to 140 mm), while stools are often 8 to 10 inches. Pneumatic posts compress when the user sits, acting as a shock absorber. Posts for big and tall chairs are engineered to higher pressure specifications to accommodate heavier weight.
There are a few chairs with manual lift adjustment, by which height is raised or lowered by rotating a threaded post. Pneumatic posts are easier to adjust and absorb shock when sitting down in the chair.
Base
Older rolling chairs office chairs used a four-legged base, but now almost all bases have five arm stars for stability. Bases may be made of welded steel, die-cast aluminum, plastics or composite materials.
Casters
Rolling chairs move on casters, which consist of a wheel or set of wheels mounted in a swivel frame. Casters can have hard wheels for carpeted floors or soft wheels for hard surfaces. Casters can be replaced on most chairs.
J. Indoor Air Quality
There are several certification programs to assure buyers that manufacturers have met indoor air quality standards. SitOnIt, National, Humanscale and HAG/Izzy have products certified by Greenguard. Greenguard offers, "Product certification program for low emitting interior building materials, furnishings, and finish systems. All GREENGUARD Certified Products have been tested for their chemical emissions performance."
HON, Gunlocke and Allsteel comply with Scientific Certification Systems (SCS) for indoor air quality certification. SCS's Indoor Advantage "subjects products to the most rigorous indoor air quality standards in the United States. Indoor Advantage tests individual components as well as overall assemblies, and provides detailed analysis of a comprehensive range of chemicals rather than a simple pass/fail for only the most common."
The Environmental Protection Agency also studies products. The November 2004 EPA Pollution Prevention Award went to Allsteel and HON:
Allsteel and The HON Company won this regional recognition from the Environmental Protection Agency for case studies at both companies. "The Allsteel #19 Chair is easy on the environment. Not only does it meet strict indoor air quality standards, but it's made from 100% recycled aluminum, 88% of the materials used in its manufacture are recyclable, and Allsteel will voluntarily reclaim any #19 chair that's no longer useful."
K. Recycled or Recyclable Materials
In addition to manufacturing with low indoor emissions, chairs may be manufactured using manufacturing processes having lower toxic emissions, parts may originate from recycled materials, or the chair is designed to be recyclable.
While many furniture companies are working hard toward being environmentally sensitive, three chairs which stand out for using environmentally sensitive manufacturing processes, use of recycled materials and recyclability at the end of the chairs' lives are:
Links to Manufacturer Environmental Policies
Hag
HON
Gunlocke
Humanscale
SitOnIt Seating
National Office Products
Planet Office Furniture and The Environment
If supporting environmentally conscious retailers is important to you, check out Planet Office Furniture's recycling efforts through its sister companies, Office Liquidators, Inc. and Corporate Environments. As of June 30, 2007, we have recycled over 25 million pounds of furniture and packing material.
L. Links to Articles and Research
This page contains links to information that will assist you in your research into chair and workstation ergonomics. Ergonomic Research & Articles Links
For more Ergonomic Chairs, Click Here.