The mechanism of an office chair

Permanent contact mechanism

The simplest mechanical version of an office chair is the permanent contact mechanism. In this asynchronous mechanism, the seat and backrest are separate from each other. Here, the seat can usually only be adjusted in height and remains fixed. The backrest can be tilted to a certain angle, allowing you to change your sitting position and relieve pressure on the intervertebral discs. The permanent contact mechanism gets its name from the fact that the backrest cannot be locked and therefore remains in constant contact with the back when freely moving. As described above, this mechanism offers only limited adjustment options. Nowadays, the asynchronous mechanism is only fitted to very inexpensive models, as it offers only a few ergonomic benefits. For this reason, it is generally not recommended for longer periods of use. For intensive daily use by one or even several people, office chairs with a tilt or synchronous mechanism are the better choice to ensure a correct sitting posture.

2. Tilt mechanism

With this type, the seat and backrest tilt backwards together as a single unit. There are two versions here, which essentially differ only in the position of the pivot point beneath the seat when tilting backwards, but this makes a noticeable difference in comfort. With the basic tilt mechanism, the pivot point is positioned centrally, which can lead to a so-called rocking chair effect, where the front of the seat rises when leaning back, causing unpleasant pressure on the thighs or around the knees. This version is more commonly found in lower-priced executive chairs as well as 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-tilt mechanism, which eliminates the shortcomings mentioned above thanks to a pivot point positioned further forward. The focus here is on an “open” mechanism at the front, causing the seating area to tilt slightly downwards. The so-called knee-tilt mechanism only allows the tilt angle to be opened or closed. The various angles can usually be locked into 2-4 positions using a lever. A pivot point at the front prevents pressure behind the knees and also reduces the risk of losing contact between the backrest and the back. This creates a certain degree of seating dynamics. On most models, the resistance of the tilt function can be adjusted to suit the user's body weight. The resulting rocking motion counteracts rigid, motionless sitting during the working day. The knee-tilt mechanism is generally fitted in executive chairs in the mid to upper price range.

3. Synchronous mechanism

High-quality office chairs are often equipped with a synchronous mechanism. The synchronous mechanism is characterised by the fact that the tilt of the backrest is linked to the tilt of the seat. If you lean back, the position of the seat changes in sync as well – it tilts slightly backwards. The ratio between the tilt of the seat and backrest can vary, but is generally 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 makes a significant contribution to improved ergonomic seating comfort.

Because both the seat and the backrest move in a defined ratio, this helps to promote blood circulation, among other things. A synchronous mechanism also enables natural movement and supports the back, as contact with the backrest is maintained at all times. This is particularly important for office workers in order to avoid physical discomfort. In addition, the synchronous mechanism prevents you from sliding upwards against the backrest (shirt-pull-out effect) and encourages regular changes of position. Office chairs with a synchronous mechanism are broadly similar to those with a tilt mechanism, but offer ergonomic advantages for users, especially thanks to the synchronised seat tilt. Many models also allow individual adjustment to your body weight.

A rotary knob or handwheel allows you to adjust the backrest resistance continuously to suit your needs. Many models also let you lock the tilt in different positions, so you can relax in the reclined position without any counterpressure. To ensure an ergonomically correct angle between the seat and backrest, the seat tilts by a few degrees at the same time. This promotes an ergonomic and healthy posture, which is especially important for people in office jobs or similar roles where they sit for long periods. All models in the ERGOHUMAN range are equipped with point-synchronous mechanism, for example. The ERGOHUMAN even features a special relaxation synchronous mechanism that enables an especially wide opening angle of up to 141°.

Other office chair mechanisms

In addition to the three most common mechanisms, there are other systems such as the 3D mechanism and the skate mechanism. With the 3D mechanism, the seat rests on a rubber joint that encourages dynamic sitting, similar to a gym ball.

The skate mechanism is similar to the synchronous mechanism, with the difference that there is no manual weight adjustment via a rotary knob; instead, your own body weight creates the counterpressure.

Conclusion

The choice of mechanism for your future office chair depends entirely on your own preferences and requirements. However, for longer periods of sitting, desk chairs with a knee-tilt mechanism or a particularly ergonomic synchronous mechanism are recommended. It is also important to pay attention to ergonomic features and a healthy sitting posture. That is why an office chair that relieves strain on your musculoskeletal system and encourages dynamic sitting is essential. However, it should be noted that although a professional office chair provides ideal support for your daily work, it is still vital to balance this with movement and give your body some variety.