By Michael Roberts, Occupational Health Physiotherapist

Ergonomic chairs are a fundamental "tool-of-the-trade" for office work. But the selection, adjustment and periodic replacement of ergonomic chairs are often a neglected component in the prevention of Occupational Overuse Syndrome (also known as Repetition Strain Injury or "RSI")

Many offices and factories we visit have poor ergonomic chairs. They are often old, in bad condition and are not set to accommodate anyone's good posture – let alone whoever uses them. We provide audit services to help sort out the good from the bad.

Click CHAIR DESIGN to continue...

The range of available ergonomic chairs is always changing; there are always chairs on the market with low quality components & foam, poor adjustment mechanisms, with seat depths too long for shorter workers and with inadequate back support. There are a myriad of design features we won't go into here. But there are several design features to check.

These days we generally recommend a tall backrest because most users want good upper back and shoulder support. Medium backrests are still useful for many individuals, but they focus on just low back support, and many of the complaints we see include soreness in the upper back, shoulders and neck.

The size and shape of the seat itself is crucial; for average sized men and women a seat depth of around 450mm will suit. The front edge should be a "waterfall" shape; curved over in front slightly to reduce pressure on the blood vessels on the underside of the thigh. For taller users a longer seat pan is recommended – ask your supplier to provide one (and change suppliers if they can't/won't!)

The gas-lift pylon can be short, medium or tall if you request one different to the one that's fitted as standard (usually medium height). There a 5 basic sizes of gas pylons, the size relating to their range of motion; most chairs are fitted with a size 3.

Arm-rests are a preference feature and should be offered if shoulder relaxation can be achieved, or if requested by the employee. It is critical to ensure that the shape of the arm-rests will not impede the users' access to the desk. Adjustable height armrests are preferable if armrests are to be selected at all. For most users we find armrests unnecessary and sometimes a real problem – if in doubt, remove them!

Click LIFESPAN & CHAIR REPLACEMENT to continue...

The average lifespan of an ergonomic chair depends on its mechanism, its structural integrity and the resilience of its foam. Without repair or reupholstering, a decent ergonomic chair, regularly used should last 5 – 7 years. Some chairs last a lot longer than this timespan. In "24/7" - type, constant use environments such as call centres, ergonomic chairs often only last 1– 2 years due to their heavy use. Purchasing a more robust chair is critical for these workplaces. A high resilience rating of all components is required such as AFARDI level 5 or 6. (AFARDI is an independent Australian furniture testing facility).

Most offices have a wide range of ergonomic chairs. We find that chairs are often old and worn out – or at least past their "use-by" dates. When chairs are worn out, they are difficult and awkward to adjust, have insufficient adjustments or have foam that does not provide comfortable support for seated employment. Worn out and inadequate chairs lead to increased strain on the users' back, neck, shoulders, arms or legs. The more frequently an individual works on an unsound chair the more risk of developing some form of cumulative strain injury.

We encourage clients to institute a routine budget for the turnover of chairs on a 5 – 7 yearly basis. Some chairs even come with a 5 year warranty, In workplaces where the chair is a frequently used toolofthetrade we recommend that the chair be selected by the user. Different shaped chairs can be made to look uniform by being covered with the same fabric.

Click THE SELECTION PROCESS to continue...

We suggest that chair selection by the users should involve testing 2, 3 or more different, ergonomically sound chairs of equivalent price range (on a week long trial basis)

Look for chairs with 5 year warranty; confirm which parts are covered by the warranty. Ask the supplier what the AFRDI rating is of the chair. The highest current rating is a 6.

To get an effective test, employees should be instructed in how to adjust their chair and encouraged to adjust position frequently for their comfort (and so they remember how to adjust the thing!) This can be initiated in a staff meeting or just communicated via a sheet that circulates with the trial chairs. The employees try out the chairs and list their preferred model or models.

The typical selection criteria we recommend are:
• 3 lever infinite adjustment
• tall backrest with long and easy up/down adjustment
• a choice of standard and long seat pans (or a seat slider)
• 10 year Dunlop Enduro foam (or equivalent)
• 5 year whole of chair warranty – implies high quality components

We trust this paper has provided you with valuable information in improving your ergonomics at work. Please feel welcome to contact us at Perform Ergonomics 0410 431 397 or Ali Roberts