The hidden cost of office chairs

It might seem fanciful to assert that office chairs are responsible for an increasing proportion of workers' compensation claims, but recent figures show musculo-skeletal injuries are increasing in office working environments. How is this happening?

If you walk into any computer-based office environment, have a look around and count how many people you can see sitting 'properly' in the way we all know is good for us. Compare that with the number perched at the front of their chairs, legs crossed, one foot on the floor, body tilted diagonally to the computer monitor, arm stretched wide to the mouse. Count the others collapsed back away from the desk, hunching shoulders forward to peer into the screen.

It is no wonder that even in relatively safe working environments such as the modern office, even with access to good ergonomic advice and furniture, back and RSI injuries are on the increase.

In the Federal Government's Comcare 2003 Annual Report, one of "the major issues in claims management (was)...increasing claim numbers, particularly the more complex claims for conditions such as...occupational overuse syndrome". Further, "there is an increasing incidence of high cost claims, particularly those for...occupational overuse injuries". These accounted for 20.8 per cent of the total cost of claims for the year. Sprains and strains and back injury added a further 43.8 per cent, making musculo-skeletal injuries a hefty 64.6 per cent of federal government employee workers' compensation claims.

People rarely wish to injure themselves. So why are employees unwilling or unable to adopt sensible ergonomic advice while working at their computers all day?

More work is now being performed when sitting than at any other time in history.

Our contemporary workforce comprises an ever-increasing proportion of computerised 'knowledge workers', typically undertaking a large number of repetitive, screen-based, data entry tasks. As such, more and more employees are becoming more and more sedentary.

The irony is that while vast quantities of global information are literally at our fingertips, our capacity to interpret and act on personal tactile information has diminished. Flat desks, flat keyboards (requiring workers to rotate in a more forward direction) are paired with soft padded seats, which often tilt the worker away from the work surface.

Technological progress and postural regress

Humans have evolved for constant movement, not to sit at workstations. We literally don't easily fit into our specialised technological environment, where certain tasks are performed over and over again. And while we are all obviously capable of sitting, human beings are not 'designed' to sit for most of the day. In many cultures, people do not - or did not - sit on chairs at all. Australian Aborigines or American Indians depicted in 18th century illustrations, for example, do not slouch or stoop; they were evidently none the worse posture-wise for a lack of chairs.

Although we all now take chairs for granted, the invention of the chair is a relatively recent event in the human time-line. Early chairs were often a symbol of status, such as a throne.

Other early chairs such as stools evolved as writing developed. Pages were leaned on raised surfaces. Paintings of medieval monks preparing illuminated manuscripts show them standing to work at large sloping desks. Other illustrations of renaissance scholars depict sloping desks above flat-topped stools or benches.

Enter the typewriter: a technical innovation requiring a flat, as opposed to a sloping, surface for use. Early typists sat on simple wooden chairs. The later swivel chairs of the early 20th century still featured flat seats with no or little padding.

Meanwhile, back at the factory, new cheaper methods of chair construction have been developed. The emergence of mass production techniques and new materials, such as injection moulding, has driven down costs.

We have evolved into a table and chair working culture where many, if not most, activities take place at a right-angled 90° sitting position. And that's not necessarily good for us.

Questionable ergonomics

It hasn't taken long for people to experience the problems created by our new way of working. Confusion has developed between what feels good, what is good, and how much a chair should cost. This has triggered the development of various ergonomic solutions for chair design, based on many questionable ideas.

Familiar examples include:

• More padding = more comfort;
• More reclining = more comfort;
• Bigger chair = more comfort;
• Lumbar support = better posture;
• More movement or 'bounce' while sitting = better posture.

There have been multiple studies into seating ergonomics and the posture that we should assume when working at school or at the office, at our desks. Many of the studies proceed from certain cultural assumptions: we somehow should "sit up straight!" as our primary school teachers instructed us. A growing body of research, beginning with FM Alexander's insights over 100 years ago through to Mandal (1987) and Cranz (1998) show that many ergonomic assumptions have been just plain wrong. Ergonomics continues to be a confused science, with many competing theories about what is best for the human body.

Confused about comfort

As shoes shape feet, so chairs shape bodies. Sitting in chairs is not a natural activity - many cultures rarely use them. Humans are immensely adaptable. Throw us off balance by putting us into a curved seat for long enough, and our bodies will reshape to suit.

This starts to affect how we organise our body parts relative to each other, even when not working at a desk. The body's accommodation to suit the chair undermines the basis of easy postural support. Eventually we feel we need a curved chair in which to cradle our deformed bodies.

Then add the idea that we should use these same chairs in which to "sit up straight" and the lumbar support merely pokes forward the sagging curve of our collapsing bodies. The way we use our body affects its ability to function well. Use affects function. Chairs have a direct impact on the way we use our bodies.

A good chair encourages healthy balance by providing firm support and easy orientation to the working task. Bad chairs progressively reorganise our bodies for the worse, leading to back and strain injuries. After this has happened, a better chair can often feel wrong at first, as our perception has been remodelled by years of sitting in poor chairs. Despite this, a better chair can provide the conditions for subsequent postural improvement and strain reduction.

The design conundrum: towards better office chair design

While chairs are obviously an important medium for good body use, particularly in an office environment, most chairs have a very weak physiological basis for their design.

In fact, many chair designers pay little regard to physiological or ergonomic issues, specifically where the principal reason for designing a chair is to make a design statement, to provide a work of art or sculpture. As Rybcynski (1987) notes in relation to interior design generally, designers are often faced with the conflict between what looks good and what feels good. Even though certain schools of design such as the Bauhaus dictum of 'form follows function' advocate the primacy of functionality, most often the style of a design wins out, leaving users with the least comfortable option.

Many of the most famous chair designs of the 20th century are at best ergonomically suspect. They look great but their utility is often quite poor. This problem is further compounded in the area of office chair design because even when a chair appears to be wholly functional, manufactured with little regard to fashion, it still may not be a good design ergonomically. The most comfortable office chair is not necessarily the best ergonomic chair. Just as a bean bag or a very soft mattress both might initially feel comfortable, over time they are likely to cause chronic back pain.

An effective design methodology

The Alexander Technique (AT) is a unique discipline dedicated to improved body use through restoring the accuracy of the proprioceptive sense. Based on the work of the Australian FM Alexander, the technique has been established for over 100 years and largely pre-dates modern ergonomic analysis. It offers an invaluable framework for human-sensitive furniture design.

Central to the technique is the concept that the relationship of the head, neck and back has a direct effect on the coordination and wellbeing of the whole person. Ideally the head needs to be balanced in such a way that the length of the spine is not compromised or compressed. Lightness and ease are possible when an equal amount of work is performed by complementary muscle groups.

By applying these ideas to chair design, Canberra-based Alexander Technique teachers Michael Stenning and Leonie John developed their innovative Active-Balance chair in 1998. Features of this chair successfully address many common failings of contemporary office chair design.

Supportive padding. Too much cushioning can cause the body to sink into a chair, constraining movement. A soft chair may be comfortable at first, but as the body sinks blood circulation lowers, skin temperature rises in affected areas, and compression under thighs increases. The pelvic bowl needs to open out against a firm surface. Overly upholstered seats allow the bones to sink and pelvic wings to turn in on themselves.

Head/neck relationship. A chair should not disturb the capacity of the person to organise and maintain an easy dynamic between the head and neck.

Maintain natural spine curvature. The spine itself should not be deformed: the two forward curves at the neck and lumbar should be maintained. The sitter should be able to pivot comfortably from the pelvis, with adequate lumbar support.

Weight distribution through the feet. Feet should be comfortably on the floor, supporting the whole weight of the legs. The weight of the torso and head should be supported through the sitting bones at the base of the pelvis (ischial tuberosities).

Multiple chair sizes. People come in many shapes and sizes, with different movement habits. Reject 'one size fits all'. Office chairs must be available in different sizes.

Multiple adjustment points. Height of backrest, tilt of seat pan, height of seat pan, and tilt of backrest are all desirable adjustments within certain parameters to accommodate a range of movements and to compensate for differing energy levels throughout the day. Adjustments should be independent and easy to use.