Understanding Office Chair Mechanisms
The mechanism is one of the most important parts of an ergonomic office chair, yet it's often one of the least understood.
When comparing chairs, you'll come across terms such as synchro, asynchro, balanced mechanism and forward seat tilt. Whilst these features may sound technical, they all relate to one thing – how the chair moves and supports your body throughout the working day.
Understanding the different types of mechanisms can help you choose a chair that's appropriate for your work and ensure you get the best from it once it's been adjusted correctly.
What Is an Office Chair Mechanism?
The mechanism is the part of the chair that controls how the seat and backrest move. It allows you to adjust your sitting position, recline, lock the chair in different positions and, on some models, alter the angle of the seat independently from the backrest.
A well-designed mechanism encourages movement whilst continuing to support your body, helping to reduce the effects of prolonged static sitting.
Fixed Mechanisms
Basic office chairs often have a fixed mechanism with little or no adjustment.
These chairs are suitable for occasional use but provide limited opportunity to tailor the chair to the individual. As a result, they are generally less suitable for people spending long periods at a workstation.
Free-Float Mechanisms
A free-float mechanism allows the seat and backrest to move independently.
This gives the user the flexibility to adjust each component separately, creating a comfortable working position whilst still allowing movement during the day.
Although less common than they once were, free-float mechanisms remain a reliable option and are still found on some ergonomic office chairs.
Synchro Mechanisms
A synchro mechanism links the movement of the seat and backrest.
As you lean backwards, both parts move together in a controlled ratio, allowing the chair to follow your natural movement whilst continuing to support your body.
This type of mechanism encourages regular posture changes and is one of the most common mechanisms found on modern ergonomic office chairs. It offers a good balance between comfort, ease of use and ergonomic support, making it suitable for a wide range of office environments.
Asynchro Mechanisms
An asynchro mechanism allows the seat and backrest to be adjusted independently.
This provides greater flexibility when fitting the chair to the individual, as each angle can be adjusted separately to achieve the desired level of support.
Because of this increased adjustability, asynchro mechanisms are often found on specialist ergonomic seating where a more personalised fit may be required.
Balanced Mechanisms
Balanced mechanisms are designed to encourage continuous movement whilst maintaining support.
Rather than simply reclining, the mechanism follows the body's natural movements, allowing small posture changes throughout the day without compromising support.
These mechanisms are commonly found on premium ergonomic seating and are designed to reduce prolonged static sitting by encouraging regular movement during normal office tasks.
Forward Seat Tilt
Some ergonomic chairs include a forward seat tilt function.
This allows the front of the seat to tilt slightly downwards, opening the angle between the hips and thighs and encouraging a more upright sitting posture.
Forward seat tilt can be particularly useful for tasks such as handwriting, drawing, drafting or other activities where you naturally lean slightly forwards.
It is generally intended for specific tasks rather than continuous use throughout the working day.
Tilt Tension
Tilt tension controls the amount of resistance you feel when leaning back in the chair.
It should be adjusted to suit your body weight, allowing the chair to move smoothly whilst continuing to provide support.
If the tension is too loose, the chair may recline too easily. If it's too tight, movement becomes restricted and the benefits of the mechanism are reduced.
If you make significant adjustments to the chair, such as changing the backrest angle or seat position, it's worth checking the tilt tension again. Altering one adjustment can change how your weight is distributed across the mechanism, meaning the resistance may need fine-tuning.
Locking Positions
Many office chairs allow the mechanism to be locked in one or more positions.
This can be useful for certain tasks or personal preference, but remaining in a single position for prolonged periods is rarely recommended.
Where possible, allow the chair to move naturally with you and remember to change your posture regularly throughout the day.
Which Mechanism Is Best?
There isn't a single mechanism that's right for everyone.
Each type has been designed to suit different chairs, working styles and user requirements. The most important factor is understanding how the mechanism works and adjusting it correctly so the chair supports you throughout the working day.
A high-quality mechanism should feel smooth, controlled and supportive, encouraging movement rather than restricting it.
Related Advice
If you're choosing a new chair, read our How to Choose an Ergonomic Office Chair guide.
Already have a chair? Our How to Adjust an Ergonomic Office Chair guide explains how to set your chair up correctly.
You may also find our guides to Understanding Lumbar Support and Understanding Seat Depth useful when selecting or adjusting an ergonomic office chair.