Office Chair Design: The Ergonomic Features That Matter Most

The design of a modern high back office chair is not a simple process and may have a profound impact on your health and wellbeing.

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Picture of Mike Karle

Mike Karle

Director and Co-founder of Karo
modern high back office chair design

“Create Healthy Workspaces”

A well-designed office chair is much more than a comfortable seat. Every component, from the seat foam and backrest to the mechanism and lumbar support, affects how your body is supported during long hours of sitting. In this article, you'll learn the engineering principles behind ergonomic chair design and what each component contributes to comfort and spinal support.

Chair design - How we engage with the product

Our initial engagement with an office chair is dependent on how we connect emotionally with the product. This may be guided by how we associate ourselves emotionally with a certain brand, and also our senses.

Before considering ergonomics, most people judge a chair by its appearance, price and perceived quality. 5 emotions that make us buy - Forbes. While these factors influence buying decisions, they have little impact on long-term comfort. The real difference lies in the chair's engineering and adjustability.

How do we sit?

Sitting is a body position in which the weight of the body is transferred to a supporting area, predominantly the ‘sitting bones’ (ischial tuberosities) and their surrounding soft tissue. There is no single best way to sit as we all differ in shape and size. There is no “one chair design” that is suitable for everyone. 

The best posture is when your body experiences minimal postural strain, in other words when we do not experience discomfort from sitting.

Discomfort from sitting arises when your muscles must counteract forces on the body. Your body’s defense against postural strain caused by sitting, is MOVEMENT. For example, fidgeting and crossing and un-crossing your legs while you sit. 

Important!

  • Every person’s back and body shape is unique.
  • Office chairs are not all the same and the level of back support afforded by each model will not suit everyone. There is no “one size fits all”, so find a chair that suits YOUR back.

Modern Chair Design - Important Factors to Consider

1. Biomechanics of sitting

In order to design a modern ergonomic office chair, designers must consider the biomechanics of sitting. When you sit, the natural inward curve of your lower back (lumbar lordosis) tends to flatten or round. This is not a neutral spinal position, so your back muscles must work harder to support your upper body.

The five vertebrae (L1 to L5) in the spine between the diaphragm and sacrum are known as the lumbar spine. This section of your spine curves slightly inward, called lordosis, before extending down to your tailbone. Breaking Back – What actually happens when you sit?

The design of the chair and how we sit affects the health of the spine. The lumbar region is the most frequently stressed during prolonged periods of sitting.

what happens when you sit and kyphosis in lumbar spine

Sitting causes 40 – 90% more strain on the back. According to a study by Cornell University, the extent of the strain depends on the individual’s physiological precondition as well as the height and slope of the work surface. The latter having a major influence on the posture of the neck and shoulders, and must therefore be considered in conjunction with the design of the seat. Should you alternate between sitting and standing at work? 

2. The chair mechanism

The mechanism largely determines how an office chair moves and adjusts, making it one of the most important ergonomic components.

This mechanical component enables you to make specific adjustments to the seat and backrest of the chair, for example, the seat height and angle of the backrest. The mechanism allows you to personalise your seat position for optimal comfort and support.

There are various types of office chair mechanisms available, the most popular being a synchronous (synchro) and free-float mechanism. What are the differences between office chair mechanisms?

synchro mechanism on office chair

i) Synchronous mechanisms

Chairs fitted with a synchro mechanism allow the angle between the backrest and seat to open (increase) when you recline in the chair. By doing so, the muscles in the lumbar region of the back are automatically stimulated. This encourages movement, helping reduce prolonged static muscle loading that can contribute to lower back pain. This movement between the seat and backrest occurs in a fixed ratio that cannot be changed. A synchro mechanism is one of the most common mechanisms found on quality ergonomic office chairs. 

ii) Free-Float mechanisms

With a free-float mechanism, the angle of the backrest and the inclination of the seat can be adjusted independently from each other. This provides greater freedom of adjustment. Orthopedic office chairs should have a free-float mechanism. These chairs are best suited for anyone with pre-existing conditions like chronic lower back pain.

No chair can completely eliminate discomfort if you remain in the same position for hours. A well-designed ergonomic chair encourages regular movement by allowing you to recline, change posture and adjust your sitting position throughout the day.

3. Design of an office chair seat

i) Height adjustability

The adjustability of the seat height is critical. A seat that is too low increases the weight on the ischial tuberosities and also causes muscular strain in the upper back and shoulders. A seat that is too high leads to increased pressure at the underside of the knee, thereby decreasing blood circulation to the lower leg and causing swelling. What is the correct ergonomic height for my desk, computer monitor and office chair?

ii) Seat depth

The depth of the seat pan should be approximately 42cm deep for fixed seats and 35 - 47cm deep for adjustable seats. Having a seat depth which is too large will prevent you from being able to use the backrest. Seat depth adjustment - what you need to know.

iii) Seat foam design

A large proportion of your body weight is concentrated through your sitting bones (ischial tuberosities). Good seat contouring and foam density distribute this pressure over a larger area, improving comfort during prolonged sitting.

Ideally, the cushioning foam should be firmer in the back and less firm and thinner in the front. If the foam cushioning is too thick, the body 'sinks' into the seat which may constrain movement. A soft seat may be comfortable at first, but as the body sinks into it, the temperature of the skin in affected areas rises and compression under the thighs increases, which then reduces blood circulation. These factors combine to increase the level of discomfort. If you're considering a mesh chair, you may also want to read our comparison of mesh and upholstered seats.

iv) Seat angle

The seat angle can alleviate postural discomfort. Orthopedic chairs, with their adjustable forward sloping seats, can reduce stress in the spine by opening the torso-leg angle to about 95o. Without a knee support, any angle greater than this will result in you sliding forward off the seat. What is an orthopedic chair?

4. The design of office chair armrests

Armrests can provide additional postural support and can aid in standing up and sitting down. There are good reasons why a chair design should incorporate armrests:

    • Armrests relieve the muscular loads on our neck, shoulders and arms.
    • They stabilise and promote good posture.
    • They ease the load placed on our back by the weight of our arms and hands, thereby reducing the stress in our back.
    • They reduce muscle stress in our legs and facilitate getting in and out of the chair.
    • Having support for our hands and underarms may provide additional strength and precision for certain types of work.
    • If you are a big and tall person that requires a heavy-duty chair, armrests provide valuable assistance in terms of getting in/out of the chair.
modern high back chair armrest design
Chairs with adjustable armrests will accommodate people of various heights and body dimensions

Because we are all different in shape and size, a modern ergonomic chair should incorporate adjustable armrests. What are the differences between office chair armrests?

orthomax orthopedic office chair
orthomax orthopedic office chair
modern chair design lumbar support
Vertical and horizontal lumbar support adjustment

5. The design of the chair backrest

Backrests form an integral part of the design of a chair and vary in size from a high to a low back.

The appropriate backrest height depends on how long you sit and the type of work you perform.

Mid-backs give some shoulder support and are frequently used for managerial and task applications. An executive chair with a high back design provides better trunk, shoulder and head support. Many modern high back chairs are in fact mid-back chairs with the addition of an adjustable headrest.

6. Lumbar support

We all have a different lumbar profile when we are sitting. Depending on how deep your inward curvature extends, an adjustable lumbar support is necessary to optimally support this area of your back.

Depending on the design of the chair, the lumbar support adjustment may be purely vertical, or it may be both vertical and horizontal (in/out). 

7. Why adjustability matters

Even the best-designed office chair cannot support everyone equally. Adjustable seat height, seat depth, lumbar support, armrests and recline allow the chair to accommodate different body shapes and working styles. The more adjustments a chair offers, the greater the likelihood it can be fitted correctly to your body.

Conclusion

A well-designed office chair supports your body by encouraging movement, maintaining a comfortable sitting posture, and allowing you to adjust the chair to your individual body shape. While aesthetics and price are important, features such as seat dimensions, mechanism design, lumbar support, and adjustability have a far greater impact on long-term comfort.

Understanding these design principles makes it much easier to choose a chair that fits your body, supports healthy sitting posture, and remains comfortable throughout the working day. If you're unsure which features you need, use our Chair Selector to compare chairs based on your body size, work style and ergonomic requirements.

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