Ergonomic Office Chairs

The chair is the single most important piece of office furniture – with the biggest impact on an individual’s health, wellbeing and productivity.

Conservatively, the cost of an office employee is £150,000 over 5 years. If a chair can improve that person’s productivity by just 2% its worth £3000 to an employer!

Just 10% of this cost will secure a very good chair, and 20% a superb chair. If you’d like to know what to look for in a great office chair read on...

Diagram: Extract from HSE ‘Seating at Work’ guide reference HSG57

Diagram: Extract from HSE ‘Seating at Work’ guide reference HSG57

Good ergonomic chairs have one characteristic in common; they have a ‘dynamic’ action that encourages movement and supports the user when adopting different postures.

It is currently possible to meet the requirements of the Health & Safety Executive’s DSE (Display Screen Equipment) guidance with ‘static’ chairs, but this is not to be encouraged.

There are various approaches to providing a dynamic action, but it’s important to understand that if you are assessing a different action to the type you are used to, you will need at least 3 days to ‘acclimatise’ to an alternative chair.

All types below are assumed to provide height adjustment and to be mounted on a stable 5-spoke base fitted with wheels – commonly referred to as ‘castors’. Castor options should include ‘hard’ for use on carpets and ‘soft’ for use on hard floors.

Back tilt

Any office chair should allow the back angle or ‘tilt’ to be adjusted independently of the seat. Almost all chairs of this type require the back to be ‘locked’ once adjusted, creating a ‘fixed’ seating position that discourages movement. Many have backs that fail to provide any support in the lower lumbar region.


Synchronous

Synchronous

This is the most commonly specified type of ergonomic mechanism, in which the seat and back move in a fixed ratio to each other. Typically, such chairs include a tension control so that the user can adjust the resistance of the mechanism to their own body-weight, allowing them to ‘free-float’ in a range of positions while being properly supported.

Importantly, good synchronous mechanisms are designed in such a way that the front part of the seat (behind the knees) does not lift as the chair reclines – this is called ‘knee-tilt’. This function allows the user to recline while keeping their feet flat on the floor, and without creating pressure (constricting blood flow) under the thighs.

Some cheaper mechanisms do not achieve this successfully; if the action of reclining causes the user to lift their feet, they will have a sensation of ‘falling backwards’, which is not conducive to comfort in the workplace!


Synchronous with automatic weight-sensing

Some manufacturers now supply synchronous mechanisms that automatically adjust to a user’s body-weight; these can be useful if a chair is located at a ‘hot-desk’ that may be used by many occupants.

However, in our experience, such chairs are very sensitive to being set at the correct height (thighs parallel to the floor or very slightly elevated) – they ‘stiffen up’ if set too high. In practice, most of us tend to sit a little too high because we use large display screens on monitor arms.

The trick to getting the best from a weight-sensing chair is to set up your seating position away from the desk – then adjust your monitor height to suit your seat height.


Tilt/Balance Mechanisms

These take a bit of getting used to, but such mechanisms really encourage user movement. Essentially, such chairs ‘rock’ on a pivot point. The user finds their point of balance, then adjusts the back forwards for a snug fit.

Subjectively, many users enjoy this rocking motion, exercising feet and ankles much more than they would on a typical synchronous chair.

Tilt Balance Chairs
Tilt Balance Chairs
Tilt Balance Chairs

‘Open-Pelvis’

‘Open-Pelvis’

These chairs reverse the usual principle of synchronous action; as the back is reclined, the rear part of the seat lifts upwards, encouraging a ‘flatter’ posture. Such chairs work very well in ‘multi-user’ situations because they adapt to user weight differences in a very positive way, at any height setting.


‘Multi-Flex’

‘Multi-Flex’

We are seeing a new generation of chairs coming to market. Materials technology has developed to the point where complex mechanisms can be replaced with materials that naturally ‘flex’ to create a pseudo-synchronous action.

In addition, the back sections allow ‘twisting’ movements that more readily adapt to any human posture while providing continual support for the spine. Such chairs require considerable investment in tooling and moulding equipment, so are available from a limited number of major manufacturers.


Breaking the Mould

Breaking the Mould

The rising popularity of sit-stand desks is demanding new approaches to seating. Sometimes, people want to alternate between standing and ‘perching’, rather than returning their desks to the traditional height (740mm from floor) HAG’s Capisco is an interesting option; a saddle stool that provides a range of interesting ‘active’ sitting options.


Height Adjusting Stool

Height Adjusting Stool

Another solution – available from a few manufacturers - is a height-adjusting stool, designed to safely tilt. As well as being relatively inexpensive, it can be tucked away under the desk when not in use, avoiding clutter in the workplace.


Finally, its worth mentioning the Kinema Active Chair – we saw this in 2016 at the Orgatec show in Cologne. This is a chair that converts from ‘traditional’ to ‘perch’ to ‘stool’ with a rotating assembly that provides a greater range of height settings than would be possible with just a gas-spring.

Kinema Active Chair
Kinema Active Chair
Kinema Active Chair
Kinema Active Chair

What are the options – and which are worth paying for?

Almost every chair is available with a range of additional options, so its important to make any cost comparison on a ‘like-for-like’ basis.

Seat slide

A sliding seat is worth having; it will allow the chair to adapt to users of different sizes. The front edge of the seat should allow a gap of about ‘three fingers’ width behind the user’s knees. Incidentally, any chair seat should have a ‘waterfall’ (softly curved) front part, to avoid constricting users’ blood-flow.


Seat forward-tilt

This is an important option for people who work in a concentrated way with display screens; such as data-entry personnel or IT specialists. It allows them a greater range of postures including sitting forward, without causing pressure under the thighs and constricting blood-flow.


Lumbar Support

Perhaps surprisingly, this is one of the least useful options. Most chair backs are designed with appropriate curvature to support the spine, and mesh backs (see ‘materials’) adapt readily to any user’s back shape, distributing pressure and support equally.

The problem is that many users think they need a lumbar support – when in practice most will adjust them in the wrong way!

Specifying a lumbar support will not harm anyone, but some types are more effective than others.

One effective innovation provided by a few suppliers is a ‘mesh tensioner’ which increases the amount of back support at a user-selectable height.


Back height adjustment

On upholstered cushion-backed chairs this is an alternative to lumbar support and effectively changes the ‘support profile’. It is not a harmful function, but should not be necessary if the back is correctly profiled.


Arms

Users like them, but HSE guidance for DSE regulations suggests that they are not necessary! If you specify arms, consider to what extent they can prevent users finding a comfortable position close to the desk. ‘Soft’ arms are ergonomically preferable, but ‘hard’ arms are less prone to damage.

Terminology for arm functions can be confusing, so here’s a guide:

2D

These go up and down – a basic requirement

3D

These also ‘slide’ forwards and backwards (or in some cases ‘rotate’), allowing the user to find a comfortable position close to the desk.

4D

These can also be adjusted for width


‘Multi-locking’ or ‘Movement-limiter’

Most chairs have the ability to ‘lock’ in a number of positions. Some offer a movement limiter, which limits the range of movement.

Arguably, there is some value in being able to lock a chair in an upright or forward-tilt position for short periods. However, given the benefits of a dynamic action, it is preferable to use a chair in a ‘free-floating’ way, adjusting the tension if necessary for a firmer feel.

Materials

Mesh

Most modern office chairs are available with mesh backs, as opposed to the more traditional upholstered fabric/foam backs. Mesh backs are popular; they adapt to the user’s natural back shape, spreading support equally and in most cases obviating the need for a separate lumbar support. In terms of design detailing, mesh-backed chairs are light and attractive.

However, mesh types do vary. Some cheaper models feature mesh that is not sufficiently tensioned to provide adequate lumbar support – and some can feel ‘plasticy’.

Some models offer the option of a mesh seat too. We find that these are less popular because they can feel over-hard. If too soft, a mesh seat can ‘bottom-out’ so the user can feel the supporting frame. If considering a mesh seat, look for a softly-rounded waterfall edge at the front, so the frame can’t ‘cut-in’ behind the knees.


Fabric and Foam

Any commercial upholstery fabric will be comfortable, flame resistant and abrasion resistant. These are typically bonded to, or stitched around, a foam inner.

However, not all foams are the same. Commercial seating must use CMHR (Combustion Modified Heat-Resistant) foams to meet appropriate standards. The better chairs use multi-density foams to enhance comfort (Softer outer layer, harder inner layer)


Leather

Often associated with ‘luxury’, leather is not the best choice for a work chair. Leather, although durable, is not very ‘breathable’ – so after prolonged sitting the user can experience ‘hot spots’. In one sense, leather is the opposite to mesh, which allows air to circulate freely around the body.


Colour

A recent trend has been to specify chairs with white frames. These can look great on day one, but are more difficult to keep clean over time, leading to a grubby appearance. Any scuffs or damage will be more difficult to conceal – so if you can, specify a black or dark-grey frame.

The area most susceptible to scuffing and damage is the chair base. Only a few manufacturers supply bases with properly designed foot-rests, so in general it is preferable to specify a ‘polished’ (metal) base. If a plastic base is specified, avoid white!

Choice of fabrics is more based on common-sense. Darker colours or multi-colour woven fabrics will conceal stains and spillages better than light colours. Most meshes are highly stain-resistant and can be brushed to remove any dust.

We hope that you have found this guide to be useful; you will probably have realised that there are many things to think about when considering this most-important item of furniture!

At Interion, we strive to offer sensible, knowledgeable and impartial advice. Please contact us if you would like any help or support finding the right chairs for your organisation.

We typically recommend undertaking a showroom tour to see what different manufacturers have to offer. Usually, we can then arrange for a few models to be delivered to your premises for longer-term evaluation by you and your colleagues.

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