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The design of a modern high back chair is not as straightforward as it may seem. Design engineers typically try to create a harmonious balance between the aesthetic appeal of the chair and it's ergonomic functionality, while constantly being aware of any price implications. Most people looking to buy a new chair only follow this thought process:
“This chair looks pretty good and the price is within my budget."
Once we have decided to buy a product, we then need to justify our purchase, not only to ourselves, but often to others as well. The importance of this "justification" is greater if the product cost more than we budgeted for!
If we are buying a modern high back office chair, we will typically use its ergonomic design functions to justify our purchase.
The ergonomic functionality of an office chair should be the first and most important aspect to consider in the purchasing process, but in reality, we focus almost exclusively on the chair's aesthetic design and price.
Modern chair design must include aesthetic appeal, price, and ergonomic functionality.
In this article I will not discuss the aesthetic and price components of chair design. Instead, I will focus on the ergonomic design functions of an office chair. Use our CHAIR SELECTOR to help you choose an office chair that suits your body shape.
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. For example:
- Colour - does it fit with our décor?
- Shape - does the chair look elegant and will it be strong enough to support me?
- Feel - how does the fabric feel and are the other components smooth?
- Smell - for example, leather has a unique smell and is often associated with luxury
- Sound - is the swivel mechanism noisy or do the plastic components sound cheap when I tap them?
Only once we have established an emotional bond with the chair, do we look at the price tag. If the price exceeds our budget, we do one of two things: be sensible and not purchase the chair, or we buy it because of emotions that make us buy.
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 our body experiences minimal postural strain, in other words when we do not experience discomfort from sitting.
Discomfort from sitting arises when our muscles must counteract forces on the body. Our body’s defence against postural strain caused by sitting, is MOVEMENT. For example, fidgeting and crossing and un-crossing our legs while we 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!
- Don’t be conned by anyone who claims that their chair design will suit "everyone”. It doesn't exist.
Modern Chair Design - Important Factors to Consider
a) Biomechanics of sitting
In order to design a modern ergonomic office chair, designers must consider the biomechanics of sitting. When we sit, the shape of the spine in the lumbar region transforms from a concave shape (lordosis) to a convex shape (kyphosis). The kyphotic shape of the lumbar region is not neutral and muscle activity is required to counteract this. Sitting in this manner can only be maintained for short periods before the muscles begin to fatigue. We experience this muscle activity as postural strain.
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 damaged during prolonged periods of sitting.
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?
b) The chair mechanism
The heart of every office chair is the mechanism which is located underneath the seat. Swivel Chairs for Home and Office
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, each design having its own pros and cons. What is the difference between office chair mechanisms?
c) 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 420mm deep for fixed seats and 350 - 470mm deep for adjustable seats.
Having a seat depth which is too large will prevent you from being able to use the back rest.
See our video guide - How to set up your chair & workstation
iii) Seat foam design
Half of your body weight is supported by only an 8% area under the ischial tuberosities or sitting bones!
Seat contouring and proper foam cushioning can distribute this weight over a larger area and rotate the pelvis forward to promote a better posture.
Ideally, the cushioning foam should be firmer in the back and less firm and thinner in the front, much like our Dual-density foam. 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.
As an alternative to an upholstered seat, some chairs have a mesh or membrane seat. A mesh seat consists of a frame over which a supporting membrane is tightly stretched. These seat designs have some practical as well as ergonomic limitations. Mesh seat chair: The pros and Cons
iv) Seat angle
The seat angle can alleviate postural discomfort.
Studies have shown that stresses on the spine are most evenly distributed when the legs are at 135o to the torso, which is the standard position of someone riding a horse.
On a conventional office chair, it is not possible to sit with such a forward sloping seat as you will simply slide off the front of the chair!
The closest one can get to this, is by using either a saddle or a kneeling chair, where the latter results in a torso-leg angle of up to 110o. Is a kneeling chair a suitable chair for me?
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?
d) 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.
- Armrests help in preventing excessive pressure on our buttocks.
- They reduce the strain on the muscles in our hands and shoulders while we work.
- 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.
Note: Armrests may not be suitable in all work environments.
Because we are all different in shape and size, every modern high back chair design should incorporate adjustable armrests. What is the best office chair armrest for me?
e) 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.
Lower backrests only support the lumbar region, and depending on the application, this may be sufficient.
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.
f) Lumbar support
We all have a different lumbar profile when we are sitting. Depending on how deep your lordosis 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). The latter is typically found on more sophisticated chairs like the Alya.
Conclusion
Each one of us is unique in our own way. We all have different preferences, needs, and requirements. This means that there is no one-size-fits-all solution when it comes to choosing an office chair. The good news is that the market is full of diverse chair designs that can be tailored to match your specific needs and provide you with the ultimate comfort and support. Whether you are taller or shorter than average, don't settle for an office chair that doesn't meet your weight rating and other individual requirements. You deserve to have a chair that can make you feel energised, focused, and productive.
Choose a chair that inspires you to do your best work every day, and never compromise on your well-being and comfort!
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