A good working posture is one that requires the least amount of static muscle work with least muscular effort. The more varied the posture the better. The correct sitting position is the critical first step in minimising the risk of back pain.

The spine is one of the most delicate parts of the human body. As demonstrated in (fig. 3), an incorrect sitting position such as slouching may result in an unhealthy curve of the spine and puts increased pressure on the soft tissues (muscles, discs and so on).

The first two illustrations (figs. 1 and 2) show the use of an upright sitting position, used in combination with a correctly positioned computer screen and keyboard. The lumbar curve is maintained in this way, which helps to reduce the pressure on the structures of the back.

Most Office chairs can be adjusted in many ways to support and allow movement to reduce the onset of discomfort. Here are the key points to remember when adjusting the chair to ensure a good working posture is achieved (please note that not all chairs provide all these adjustments):

•  Initially sit at the desk, looking squarely at the computer. You are now ready to adjust your chair.
•  Firstly, adjust the seat height so that your elbows are resting slightly higher than the desk surface(shoulders relaxed). Your thighs should be between 90-95 degrees to the upright body. You may require a footrest if your feet are not comfortably flat on the floor. The top of the display screen should be approximately at eye level (you may need to raise the screen) see fig. 1.
•  Secondly, adjust the seat depth - that is the horizontal part of the chair seat - so that you can sit firmly against the back pad with a small gap between the front of the seat pad and the back of your knees.
•  Next the height of your backrest should be adjusted to match the small of the back. To avoid neck and shoulder tension, shoulders should be relaxed. Additional neck support is generally only required where the person benefits from leaning back to change their posture and requires further support. It is rarely used whilst the person is working; more when they are reclining.
•  Sitting in your normal working posture, your forearms should rest slightly higher than the working surface, whether the keyboard, the mouse, or paperwork. Armrests are to be used when resting and encourage you to lean back and take the strain off your upper limbs.
•  Lastly, release the seat and back locking mechanism so the chair can move freely. This free movement encourages your muscles to work and to help your circulation. It greatly helps to reduce discomfort in a sedentary job.