It is a very common occurrence: You are sitting on a comfortable swivel chair working on your desktop computer or laptop. You are very focussed and concentrating deeply, and you have been sitting there for hours. When you finally raise yourself from the keyboard for a moment, you stretch heaven-wards, give a big sigh, and then rub your hands along the small of your back. You feel the dull ache right along your spine, and it is a familiar feeling. You've got a back pain and you have had it for a long time.

If you stopped to think about it for a moment, you would recognise an important fact about your seated posture that is contributing to your back ache. Whilst your comfortable, padded, computer chair has a large, ergonomically-shaped backrest, you hardly ever use it. When you are typing away intently on the computer, you tend to lean into the computer with your body is arched forwards.

To many people, it seems unnatural to lean backwards into the comfort of you chair when you are typing away at the keyboard. The position of the keyboard on the desk in relation to your seated position seems to require you to lean forwards. Many people who have recognised this problem and seek an appropriate ergonomic chair to 'fix' it ask for a chair that will maintain supportive contact with their back as they lean forwards into their computer.

Thankfully, such chairs are not commonplace. 'Thankfully', because such chairs would be supporting an unnatural posture rather than fixing it. The angle between the backrest of your computer chair and the seat of the chair should be 90 degrees or greater. It would be very unnatural and uncomfortable for your chair to constrict your body into an angle of less than 90 degrees.

So how then do you get your chair to support your back as you work on the computer or on paperwork at your desk? The answer is to use a chair that encourages you to sit up rather than lean forwards, and makes it comfortable for you to do so. You will find this feature in 3-lever computer operator chairs and 3-lever ergonomic computer chairs. On 3-lever chairs, one lever adjusts the seat height on the gas lift as usual; a second lever adjusts the recline angle of the backrest in relation to the seat, and the third lever adjusts the angle of the seat. The combination of the second and third levers provides you with a much wider range of options than you would get out of the second lever of a 2-lever chair. Because while you can use the second lever to recline the backrest backwards, you can use the third lever to tilt the seat forwards. The combination of the second and third levers will never reduce your seated angle below 90 degrees. Instead, by tilting the seat forwards, the 3rd lever encourages you to sit upright, and makes it more comfortable for you to do so. Therefore if you lock the backrest into the upright position (using the second lever) and tilt the seat forwards (using the third lever), you will find that you can sit upright, rest your back on the chair's backrest, and type away at the computer without leaning forwards uncomfortably.

This should help you avoid (or at least reduce) those nasty back aches you get when you rouse yourself from hours of concentrated typing at the computer.