How to correctly adjust the seat height on your chair

HOW TO CORRECTLY ADJUST THE SEAT HEIGHT ON YOUR CHAIR

AT A GLANCE

  • Improving and maintaining the health of your spine is one of the best investments you can make.
  • Prolonged and inappropriate sitting has detrimental effects on the health of your spine and your health in general.
  • Back pain and neck problems have reached epidemic proportions in all countries where sitting for long periods became the norm.
  • Correctly adjusting the seat of your office chair will help you maintain the S-shaped natural curvature of your spine while sitting, which will in turn help mitigate detrimental effects of sitting on your spinal column and back muscles.
  • The slight forward tilt of the seat of your chair is necessary for maintaining the natural curvature of your spine during sitting.
  • For a long time, ergonomics experts were suggesting that upright sitting with 90 degrees angle between the thighs and the torso is the correct way to sit.
  • The only effective way to effortlessly maintain the S-shaped natural curvature of the spine while sitting is through slightly declined sitting posture where our thighs are inclined with the buttocks higher than the knees, and the angle between the thighs and the torso is greater than 90 degrees.

It is a well-known fact that work-related musculoskeletal disorders today represent one of the major causes of work absenteeism while back pain and particularly lower back pain cause more disability than any other condition.

Prolonged sitting forces a static posture, which increases stress in the back and other parts of the body adding significant pressure on the spinal column and back muscles. As our bodies are designed for movement and not for sitting still in a static position over long periods, we are paying a high price for misusing our bodies in this way.

Although it would be quite difficult for most of us to escape prevalent sedentary work conditions imposed by the contemporary society and suddenly switch to a Paleolithic lifestyle to allow ourselves to start using our bodies in a way our hunter-gatherer ancestors did, there certainly are things that we can do to minimise the health hazards of sitting.

WHAT CAN BE DONE

Choosing a chair that adequately supports those different parts of the body that need support while at the same time providing for the body’s need for freedom and frequent variation of positions is certainly a good start.

However, something relatively simple and fundamental that any of us can do to improve the way we sit has to do with finding an ideal seat height in combination with the correct angle of the seat we use.  

CURRENT DOGMA

With a level of current scientific knowledge available, one would easily assume that a firmly settled consensus on the correct sitting position already exists and that there is not much to discuss on this issue. However, you might be surprised to learn that the traditional upright sitting posture where the torso and neck are approximately vertical and in line, the thighs are horizontal, and the lower legs are vertical, actually does not work well. The reason this posture is not ideal for your spine is that it causes the S-shaped natural curvature of the spine to collapse along with the tension in your back muscles having to work hard to maintain the upright posture by correcting the collapsed spine.

We are told that the way to help ourselves to maintain the proper shape of the spine while keeping an upright sitting posture is by using an appropriate backrest which will provide adequate lower back support. Again, this only helps for a very limited period after which we inevitably start feeling uncomfortable and need to change the position.

Truth be told, there is no perfect sitting position and I believe that the only perfect sitting position is the next one, as our bodies have a natural need for frequent variation of sitting positions, even if this change means to only slightly shift the way we sit and use available support.

Nevertheless, it is important that the chair we sit on allows us to use our bodies in harmony with its natural design so that we do not spend too much time in an unnatural, forced and static position, which moulds our bodies contrary to its natural form.

We retain S-shaped natural curves of our spine easily when we stand. When we sit down, the more the angle between the thighs and the torso closes, the more we tend to lose the springy shape of our spine, which inevitably leads to flattening of its natural curves making sitting for a longer period a rather uncomfortable task.

Spinal curves are extremely important as they allow the spine to act like an S-shaped spring helping it to evenly distribute the stress and strain placed on it by different factors and to maintain balance while sitting or standing.

Sitting in the traditional upright position as described above, actually does not allow the hips to bend for more than around 60 degrees, although the angle between the torso and the thighs might look as open enough to reach 90 degrees.

If you would like to know more about how and why this happens you can check a more detailed explanation of this phenomenon by a Danish physician A. C. Mandal

...The minimum that you can do to improve the quality of your sitting and protect the health of your spine is by using an office chair or work chair in general which will ideally allow slight forward tilt and by adjusting the seat height so that your buttocks are higher than the knees so that the angle between the thighs and the torso is greater than 90 degrees

QUICK TIP TO IMPROVE THE QUALITY OF YOUR SITTING

I remember when in 2014, The Society of Teachers of the Alexander Technique (STAT) started campaigning for changes to the European standard that allowed a school chair to slope backwards by five degrees. The campaign which achieved some limited results was calling for the introduction of a plus 10 degree forward tilt to school chair seat technical specifications thus creating chairs with slight forward tilt and requested that further scientific research was to be commissioned into how school furniture can affect children’s wellbeing.

In case you were wondering why so many children suffer from back pain as a result of being forced to sit on backward sloping seats in spite of clear evidence about how detrimental this is for the health of the spine, you might be surprised to learn that the main reason for this is that the design of these chairs allows for stacking them easily.

As a part of their efforts to help school children, STAT activists introduced a simple solution consisting out of a forward sloping seat cushion that corrects the backward sloping seat by turning it into a forward sloping seat.  

In conclusion, the minimum that you can do to improve the quality of your sitting and protect the health of your spine is by using an office chair or work chair in general which will ideally allow slight forward tilt and by adjusting the seat height so that your buttocks are higher than the knees so that the angle between the thighs and the torso is greater than 90 degrees.

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