The mechanics of an office chair

Permanent mechanics

The simplest mechanical variant of an office chair is the permanent mechanism. With this asynchronous mechanism, the seat and backrest are separate from each other. The seat can usually only be adjusted in height and remains rigid. The backrest can be tilted to a certain angle so that the sitting position can be changed and the pressure on the intervertebral discs can be relieved. The permanent contact mechanism gets its name from the fact that the non-lockable backrest is in constant contact with the back when swinging freely. As just described, this mechanism only offers a few adjustment options. Nowadays, the asynchronous mechanics are only installed in very cheap models, as they only have a few ergonomic aspects. Therefore, it is not recommended for longer periods of use. When used intensively on a daily basis by one or even several people, office chairs with a rocker or synchronous mechanism are the better choice in order to be able to adopt a correct sitting posture.

Rocker mechanism

In this type, the seat and backrest tilt backwards as a single unit. There are two variants that basically only differ in their axis pivot point, below the seat, when tilted backwards, which means a significant increase in comfort. With the simple rocking mechanism, the pivot point is set in the middle, so a so-called rocking chair effect can occur, in which the seat in the front area goes up when leaning back, causing unpleasant pressure in the thigh or knee area. This variant is more likely to be installed in inexpensive executive chairs or visitor or conference chairs and is not intended for prolonged use at a desk or for active work.

The higher quality version of this mechanism is the knee rocker mechanism, which eliminates the above-mentioned shortcomings by having a pivot point further forward. The focus in this context is on an “open” mechanism in the front part, which causes the buttocks area to tilt slightly downwards. The so-called knee rocker mechanism only allows the tilt to be opened or closed. The different angles can be locked in 2-4 positions, usually using a lever. A pivot point in the front area prevents, on the one hand, the back of the knee from being pressed in and, on the other hand, the possible loss of contact between the backrest and the back. This creates a certain seating dynamic. On most models, the resistance of the rocking function can be adjusted according to body weight. The resulting rocking counteracts rigid, motionless sitting in everyday work. The knee rocker mechanism is usually installed in executive chairs that are in a medium to high price range.

Synchronous mechanism

High-quality office chairs are often equipped with a synchronous mechanism. The synchronous mechanism is characterized by the fact that the inclination of the backrest is linked to the inclination of the seat. If you lean backwards, the orientation of your seat also changes at the same time - it tilts backwards slightly. The ratio of the change in inclination between seat and backrest can vary, but is usually implemented at 1:3. This design ensures that the originally selected support point for the pelvis is always maintained, regardless of your sitting position. This contributes significantly to improved, ergonomic seating comfort.

The fact that both the seat and the backrest change in a certain ratio promotes blood circulation, among other things. In addition, a synchronous mechanism enables natural movements and supports the back as contact with the backrest is always maintained. This is particularly important for office workers in order to avoid physical discomfort. In addition, the synchronous mechanism prevents the backrest from sliding up (shirt-taking effect) and encourages regular changes of position. Office chairs with synchronous mechanisms are similar in the broadest sense to those with rocking mechanisms, but offer ergonomic advantages for users, especially thanks to the synchronized seat tilt. Many models also allow individual adjustment to your body weight.

A rotary knob or a handwheel allows you to continuously adjust the backrest's counter pressure to suit your needs. Many models also have the option of fixing the inclination in different positions, so that you can relax in the lying position without counter pressure. In order to guarantee an ergonomically correct angle between the seat and backrest, the seat tilts by a few degrees at the same time. This ensures an ergonomic and healthy posture, which is particularly important for people in office jobs or similar jobs where they sit for long periods of time. For example, all models are equipped with a point synchronous mechanism ERGOHUMAN series equipped. The ERGOHUMAN even has a special relax synchronous mechanism that enables a particularly large opening angle of up to 141°.

Other mechanics on office chairs

In addition to the three most widespread mechanics, there are also other functions such as the 3D mechanics or the skate mechanics. With the 3D mechanics, the seat rests on a rubber joint, which promotes dynamic sitting, similar to a sitting ball. 

The skate mechanics are similar to the synchronous mechanics with the special feature that there is no manual weight adjustment using a rotary knob, but rather your own body weight creates the counter pressure.

Conclusion

Which mechanics your future office chair should have is entirely up to your ideas and requirements. However, for longer periods of time, desk chairs with a knee rocker mechanism or a particularly ergonomic synchronous mechanism are recommended. It is also important to pay attention to ergonomic aspects and a healthy sitting posture. Therefore, an office chair that relieves the strain on your supporting system and promotes dynamic sitting is essential. However, it must be noted that you have a Professional office chair Although it provides optimal support for daily work, it is essential to create a balance of movement and thus offer the body variety.