Sitting at the Computer

New problems emerged in the electronic office

Enforced static posture is bad

Working at a fixed location while operating a computer keyboard resulted in a forced static posture. It was not possible to use the lean back setting on an office chair and remain productive; no wonder only managers used comfortable office chairs.

This was less of a problem in the days of typewriters, for the typical clerical worker spent some time moving to and from physical filing cabinets, fetching paper and carbon sheets, replacing ribbons and so on. The old mechanical typewriters also required full arm displacement to depress the keys, which kept the shoulder girdle in motion. The relatively large physical motions needed to return the carriage also helped to break monotony. Workers confined to a computer workplace through which virtual filing in a paperless office was achieved almost instantly at the tap of a key, found insufficient time to break up their tasks with other kinds of physical activity. The emergence of the computer work place and its ubiquity in the contemporary office has focused attention to the short comings of the general working chair, desk and keyboard combination.

Unsupported sitting

The lumbar support of luxury seats can lead to atrophy of the lower dorsal musculature over the long term, increasing risk of back injury when the user is occupied with more demanding tasks at other times; weeding in the garden, for example. The managers may be more comfortable in their reclining seats, but that does not mean they are healthier for it. Data input typists and call centre workers are now able to use comfortable supporting chairs, but because of the monotony of their work, static load induced discomfort and injury have emerged as common work place hazards.

The diagram at the left (menu frame) shows a posture claimed by many to be healthy because it forces users to employ the dorsal musculature of their back in order to remain upright, and permits greater freedom of movement; we might refer to this as the rigid poker upright Victorian posture. While Victorian ladies had the support, for better of worse, of laced whale bone trussed corsets, contemporary workers have little to aid them. In reality, it is not possible to sit like this for more than fifteen minutes or so. As muscles become tired workers typically slump into unhealthy postures. The slumped posture is not only bad for the lower back in the long term, but also inhibits breathing, leading to long and short term problems such as increased fatigue and reduced physical fitness in addition to the RSI risk.

Best of a bad deal

The 3 x 90 with lumbar support

This upright posture with lumbar support is often recommended.
Resting the hands on the lap can take some burden off the spinal column.

For a long time it was believed that lumbar support to assist the worker maintain an upright posture would be sufficient, as shown in the figure to the left, with elbow, hip and knee angles at 90 degrees. However, in practice most office workers are not able to keep their backs erect for long periods. Scandaniavian research shows that 50% of office workers slump in their chairs within ten minutes of starting work, even if they are trained to sit vertically. Resting the hands on the lap or arm rests can take up to 25% of the load off the lower back.

Leaning backwards ocassionally takes nearly all the compressive force off the lumbar vertebrae
This posture is quite comfortable and not harmful for short periods.

Although occasional leaning back and stretching is helpful (indeed, should be encouraged), and slumping down while supported by the elbows can be helpful for short periods, these postures cannot (and should not) be maintained for long periods. Of course, no active work can be undertaken like this. The rounded shoulders posture, to the right, causes strain on the upper neck if the person raises their head to look at a monitor, another person or other object placed at normal working height. Habitually sitting like this while trying to work can give rise to uppercervical dorsal root compression.

Most of us have spent many hours writing at a desk in this position.

Using the table as a support is not too bad, since much of the weight of the torso is taken up by the arms, and is often seen among workers using lap top computers placed on a table. Research shows that inter-vertebral pressure is low despite the tendency for kyphosis in the lower back. However, it is not recommended for long periods of intensive work, for it places greater stress on the shoulders and neck, it tends to demobilise the worker and it stretches the inter-spinal ligaments - especially in the lumbar region - which weakens the lower back in the long term.

What do we see in reality?

The worst of all possible worlds

Going hard at it when you are tired can be very damaging to your spinal column.

Motivated workers tend to press on when back fatigue in the dorsal muscles does not permit a vertical posture, taking a position on the edge of their chairs and leaning forwards. This relieves the fatigue on the dorsal muscles at the cost of dangerously increased intervertebral pressure, and if the individual is peering at a computer monitor for long periods neck injury can result. This injury is not only muscular, but may include compression of the nerve roots, in the cervical, upper thoracic and (because of kyphosis in the lower back) lumbar regions. Fibromyalgia or the neck and shoulder muscles are often seen in individuals who habitually work in this posture. In these cases psychological and work pressure play a role in the aetiology of the work related musculoskeletal disorders (WRMD) or repetitive strain injury (RSI), as these conditions are commonly known.

The most common slump; a typical bad posture

Alas, most computer users spend most of the time like this: very bad!

Slumping for short periods is not a problem, but the posture shown to the left is often assumed for long periods, which places stress on all levels of the back, neck, shoulders and arms. Unfortunately, this is the most commonly observed posture among workers who do not have suitable work place furniture, and who take insufficient breaks during their working day. Prescribing the 3 x 90 posture turns out in practice to be wishful thinking.