Postural dynamics | BRUNAULT Ergonomic Add-ons

Postural Dynamics

Posture is defined as the position of the body in space.

However, if we pay attention to how the vertebrae and discs of the spine are formed and how the body behaves when standing and under the daily stress of gravity, posture is much more than that.

The spine, viewed from the side, is constructed with the vertebrae and intervertebral discs forming a lumbar, dorsal and cervical curve (Figure 1.1). The intervertebral discs are anteriorly angled (A) and the facets are close together (B) (figure 1.2).

Concept of the Design of BRUNAULT Lombar Supports (3)

Figure 1.1

A (4)

Figure 1.2

Relaxing Posture

When the curves are present, the body is in a parasympathetic posture.

  • The parasympathetic posture refers to the parasympathetic nervous system which corresponds to a "relaxing posture".
  • It induces a general slowing down of the body's functions. The heart rate and respiratory activity are slowed down and blood pressure is lowered.
  • Digestive function and sexual appetite are promoted.
  • It is therefore in this posture that the body's repair process can take place (innate power of the body to heal itself).
  • When mental stress is reduced and all the muscles of the body relax, it is at this particular moment that blood circulation is facilitated and more nutrients can reach all parts of the body.

The body can adopt a relaxed posture only when sitting or lying down.

In the supine position, the parasympathetic nervous system is at its highest level of operation.

In a sitting position, the parasympathetic nervous system can be active at a lower level of operation, as long as the body adopts a posture that allows the muscles of the back, shoulders and neck to relax.

In the standing position, the parasympathetic nervous system is at its lowest level of operation.

In the standing position, the relaxing posture is almost impractical.

Try it for yourself:

  1. Arch your lower back and maintain this position...
  2. Bring the tip of your sternum down directly in line with your pubis and keep this position.
  3. Then tilt your head back until your jaw is parallel to the ground and stay in this position.

There, your body is in the relaxing posture!

Now try to walk, try to work...

Benefits of the Relaxing Posture :

  1. Parasympathetic nervous system is active
  2. Relaxation of back, shoulder and neck muscles
  3. Opening of the rib cage (facilitates breathing)
  4. Opening of the abdominal space (facilitates digestion)
  5. Facilitated blood circulation
  6. Increased nutrient intake
  7. Repair and energetic recharging of back, shoulder and neck muscles
  8. More muscular endurance in sitting position
  9. Reduction of fatigue and muscle pain

The disadvantages:

  1. Inefficient work and sports posture
  2. Joints too flexible
  3. More risk of joint damage

Stress Posture

When we are standing, our muscles instinctively stiffen to prepare the body to be ready for the stress coming from our immediate environment.

The body is in a sympathetic posture:

  • The sympathetic posture refers to the sympathetic nervous system, which corresponds to a "stress posture".
  • When the body is standing, it activates the sympathetic nervous system which prepares it for action.
  • In response to stress, it orchestrates the so-called fight or flight response, which leads to dilation of the bronchial tubes, increased cardiac and respiratory activity, increased blood pressure, dilation of the pupils, increased sweating, decreased digestive activity...
  • The contraction of the muscles of the back, shoulders and neck in order to sag the curves of the spine and compact the joints to increase their capacity to absorb the pressure of shocks.

If you pay attention to your working posture, no matter what work you do, (1) you hold your head and shoulders bent forward (tense neck and shoulder muscles and sagging cervical curve) and (2) you need to bend forward to be closer to your project (sagging lumbar curve) (Figure 2.1).


Figure 2.1

When we are in action, in order to protect ourselves and be more efficient, the body naturally : (1) flatten the intervertebral discs (C) to effectively absorb the vertical pressure that gravity puts on us, in addition to the pressure of the weight of our body and the objects we carry (Figure 2.2) and (2) hold the facets (D) apart (Figure 2.2 and 2.3) to avoid causing a fracture (Figure 2.4).


Figure 2.2

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Figure 2.3

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Figure 2.4

Advantages :

  1. Sympathetic nervous system is active
  2. The body can put itself in all types of postures to accomplish our work tasks as well as to enjoy our leisure and physical activities
  3. The body can effectively take the blows without damaging joints and nerves


  1. Sustained contraction of the muscles of the back, shoulders and neck
  2. Compression of the rib cage (more difficult breathing)
  3. Compression of the abdominal space (more difficult digestion)
  4. More difficult blood circulation
  5. Less nutrient supply to the muscles
  6. Deterioration and energetic exhaustion of back, shoulder and neck muscles
  7. Less muscular endurance in sitting position
  8. Increased fatigue and muscle pain

Health is the balance between the relaxation posture and the stress posture ...

Sleeping all day (Relaxing posture), we know it, we become lazy and weak!

On the other hand, working 12 hours a day, 7 days a week (Stress posture), we become irritable and our body becomes tense, exhausted and damages itself more quickly!

So how can we create balance between sleeping and working?

In the sitting position!

Most of us spend more than 9 hours a day sitting. We spend more time sitting than lying down!

To maintain balance while sitting, whether at work in front of the computer, the workstation, in the car, in front of the television, on public transit..., our posture must return to a relaxing posture so that the parasympathetic nervous system can be activated to recharge our muscles with nutrients and energy.

But do the backrests of today's chairs, seats and armchairs support the relaxing posture (Figure 3.1)?

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No, it's not!

On the contrary, they promote the stress posture (sagging lumbar curve - upper back bent forward) (Figures 3.2 and 3.2a), thus leading to deterioration and energy depletion of the back, shoulder and neck muscles, which in turn leads to general fatigue of the body.

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C (2)

Figure 3.2a

L-3 (3)

Figure 3.3a

How to activate the parasympathetic nervous system while sitting down?

It is simply a matter of filling the space between the lower back and the backrest to tilt the upper back back while leaning comfortably to position the body in its relaxing posture (Figures 3.3 and 3.3a).

It is for these particular reasons that we developed the design of our ergonomic lumbar add-ons.

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