You know that:
- prolonged sitting can cause or exacerbate back pain
- static postures increase the stress on the back, shoulders, arms, legs, and in particular, can add large amounts of pressure to the back muscles and spinal discs.
The image below illustrates that sitting already places larger pressures through the discs in our back when compared to standing. We can also see from looking below that sitting with poor posture further increases disc pressure.
When sitting for prolonged times people tend to slouch forwards or down into their chair. This posture can stress spinal ligaments and strain the discs and surrounding structures in the spine. An ergonomic chair can help maximise support and maintain good posture while sitting. There is no one best chair however there are a number of features to look for when picking a good chair.
Selecting a chair
When you are selecting your chair – make sure that you sit on a few different ones. Comfort and fit is very important. Then, look for the following features.
Adjustable seat height: This allows the user to have his or her feet flat on the floor, thighs roughly horizontal to the ground and arms even to the desk.
Seat width and depth: The seat should have enough width to support the user comfortably without them having to squeeze into it. The depth of the chair needs to be deep enough so the person can sit with their back supported by the backrest while also leaving around 3 inches between the back of the knees and edge of the seat.
Lower back support: The lower spine has a natural inwards curve, sitting for long periods tends to flatten out this curve placing stress on the lower spine. A chair which has adjustable lumbar support (both height and depth) is important so each person who uses the chair can get proper support.
Backrest: The backrest should be wide enough to cover the majority of the width of the back, if it is separate from the seat it should be adjustable in height and angle. Again the back rest should pay special attention to lower back support.
Seat material: Having a comfortable material and fabric that breaths is preferable. The sitting surface should offer good cushioning for extended sitting periods.
Armrests: Armrests are optional, if the chair has them they should be adjustable and allow the forearms to rest comfortably and shoulders to be relaxed. The elbows should rest lightly and the forearms should not be on the arm rest while typing.
Swivel: A swivel is necessary so the user can reach different areas on his or her desk without having to twist awkwardly or stand.
How should you be sitting?
When sitting it is important to have ears, shoulders and hips roughly in line as pictured above. The thighs should roughly be horizontal to the ground, they should never be placed higher than the hip joint. Feet should also be placed flat on the ground or on footrest or stool. Arms should also be roughly placed at 90 degrees. Keyboards, phones and other commonly used office equipment should be in arms distance. Even with the great posture you are not doing your body any favours by staying in one position for too long. Your muscles will get fatigued. So try and change activity or get up and walk when possible (e.g. to the printer, fax machine, toilet, coffee room or water cooler).