The Science of Ergonomics
Our bodies aren’t designed for us to stay sitting down for half or more of our waking hours – but for many of us, this has become the norm. Luckily, advances in ergonomic chair design have minimized the strain that long periods of sitting put on people’s spines, helping keep us comfortable and healthy.
Lumbar support
The lumbar region of the back has a natural inward curve. Ergonomic chairs are designed to support this curve. They prevent slouching, which causes the curve to straighten and increases pressure on the lower spine.
Many chairs have backrests that are large enough to support not only the lumbar region, but the middle and upper back areas and the shoulder blades too. Chairs with backrests that are too small or low aren’t recommended because they may force you into a slouch.
Seat pan and depth
The pan, or horizontal plane, of a chair should enable you to keep your feet flat on the floor. If the backrest of the chair is designed to tilt, the pan should move accordingly. The depth of the seat pan is also a consideration. If the pan is too short, it will result in pressure on the back of the thighs. A pan that is too long forces you to prop yourself forward, putting pressure on the back of the knees. The pan on a chair isn’t always fixed. Seats with adjustable, sliding pans are available too.
Wheels and swivelling
Wheels and the swivel function of a chair make the chair easier to slide toward and away from your desk. The wheels remove the need to pick the chair up us you move back, and the swivel allows you to turn your back away from your work area without straining your back muscles. This is especially important because the back muscles are more vulnerable to injury after you’ve been sitting still for some time.
Proper cushioning with good quality foam will stop a chair from taking an impression of the person sitting on it, and contribute significantly to comfort. Fabric upholstery is typically a better choice than leather because it can breathe, stopping the seat from heating up too much.
Armrests
Ideally the height of armrests should be adjustable. On average, they should be between 20 and 25 centimetres from the seat pan so that they provide proper support for the arms at the elbow and forearm. A properly adjusted armrest prevents you from having to droop or raise your shoulders.
Seat height
The height of a good office chair is adjustable, usually with the assistance of a hydraulic cylinder. On average, a seat height of between 45 and 60 centimetres is suitable for most people. This leaves the feet comfortably touching the floor, without requiring that the knees bend beyond 90 degrees.
Reclining backrest
Leaning back takes pressure off the spine and sitting bones, so it’s important to do this periodically if you’re seated for long periods. Ergonomically designed office chairs allow for this by providing reclining backrests. Ideally the angle of the seat pan should adjust as the backrest is tilted to ensure that your spine is properly supported in various postures.
