Developing FM
| An ergonomics guide to office seating |
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| Written by Levent Çaglar, Senior Consultant Ergonomist, FIRA International, 2008 | |
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The most ergonomic office chairs exceed the minimum criteria specified by safety regulations to contribute to the wellbeing and efficiency of the workforce. Levent Çaglar of FIRA International offers some advice and guidelines for making the optimum choice in office seating.
People are spending more and more time sitting down. A lot of leisure time is spent on a sofa watching TV, reading or eating; travel involves sitting in cars, coaches, trains or planes; and at work, many workers sit for much of the time, and with the advent of the electronic office, people perform more tasks in the same seat. What is good seating?Ergonomically correct and comfortable seating should provide stable body support in a variety of postures over a period of time. It should also be appropriate to the tasks or activities that may be performed by the person sitting on the chair. The main requirements for good seating are that:
How does the task affect the choice of chair?In a work environment, chairs should not be considered in isolation but in conjunction with the work surface, because the chair should suit both the height of the workstation and the needs of the user. The distance between the seat and work surface should be 210-300mm, whilst maintaining at least 170mm between the underside of the work surface and the seat. Ergonomic and comfortable seating depends mainly on what the person sitting in the chair will be doing. In general, the work people do in offices falls into two main categories: multi-task or dedicated-task work. Multi-task workAs the name suggests, multi-task work involves carrying out a number of different tasks, some of them simultaneously. Multi-task workers generally move around a great deal in their offices. They might be reading, writing, using a computer, answering a telephone, accessing a number of documents on and around the workstation and having meetings with other people. In ergonomics terms, multi-task work is almost ideal, because constant changing of tasks makes the adoption of different postures essential. Changing posture allows muscles to alternate between tension and relaxation, and allows spinal discs to compress and decompress. This encourages blood flow and hence prevents any build-up of pressure on buttocks, legs and backs. Therefore a multi-task chair should allow body movements whilst maintaining good support, especially for the lower back. Dedicated-task workDedicated-task work is usually highly repetitive and requires the worker to sit in a relatively fixed posture for extended periods. Such workers are deskbound and normally carry out a single task. A good example of this would be call centre workers. As a task becomes more dedicated, the person becomes less and less able to move. Dedicated-task work causes certain muscles to work continuously (in order to keep the body upright). It also reduces blood circulation to insufficient levels at which it becomes difficult to eliminate the accumulated lactic acid during continuous muscle contraction. There is some clinical evidence that such physiological effects of dedicated-task work contribute to back problems among office workers. There is nothing worse than having a chair with numerous complicated controls that either users do not bother with or adjust incorrectly. A comprehensive user manual for the chair is needed, and should explain the use of the controls and illustrate how to achieve good, appropriate and comfortable postures. In addition, workers should be given training to ensure they are familiar with the controls for each adjustment appropriate to the tasks they need to perform. RegulationsThe Display Screen Equipment (DSE) regulations affect today's office workers. These were introduced in 1992 by the Health and Safety Executive (HSE) to implement the so-called European VDU directive, and were revised in 2003 to include laptops, but there have been no changes regarding chairs or desks. DSE regulations have a number of minimum requirements with which all equipment, including chairs and desks, must comply. The schedule to the DSE regulations state the following requirements for a chair in use at a DSE workstation:
These are very general, but HSE's accompanying guidance document states: "The primary requirement here is that the work chair should allow users to achieve a comfortable position. The schedule requires the seat to be adjustable in height (i.e. relative to the ground) and the seat back to be adjustable in height (also relative to the ground) and tilt. “Provided the chair design meets these requirements and allows the user to achieve a comfortable posture, it is not necessary for the height or tilt of the seat back to be adjustable independently of the seat. Automatic backrest adjustments are acceptable if they provide adequate back support." HSE guidance also states that the equipment (including chair and desk) that complies with the requirements of BS EN ISO 9241 will meet the requirements of the regulations. It also refers to dimensional and safety standards, which are listed below. Checklist/selection criteria
Chairs meeting these standards will only fulfil minimum requirements of the regulations. Compliance with the above standards is only the starting point in the selection of a good office chair. The following guidelines should help you to identify good ergonomic chairs that go beyond the minimum requirements of the regulations. Such chairs should improve the wellbeing and efficiency of the workforce and should eliminate or minimise the occurrence of musculoskeletal disorders and possible subsequent litigation and costly compensation:
Any selection process should include user trials. Having identified three or four chairs by the above process, these chairs should be tried at least for a week by the staff at their workstations. A carefully designed questionnaire should be administered. Analysis of these questionnaires would pinpoint the chair that matches the needs of your workforce, the tasks they carry out and also the ones they like. Levent Çaglar is Senior Consultant Ergonomist at FIRA International. Please visit www.fira.co.uk |
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