The reason is quite simple!
In the skin, blood circulates through small blood vessels (capillaries).
In the case of a hollow back resting against a flat backrest, the skin around the shoulder blades is compressed, compared with the hollow back, which does not.
What we don't realize is that too much direct pressure on the skin prevents the blood from circulating and causes cells to die.
To defend itself, the body will naturally, and in spite of ourselves, always want to spread the pressure so that the blood flows again.
To do this, in this case, the body will force the small of the back against the backrest.
Knowing this, if the lumbar support puts direct pressure in the middle of the lumbar curve, the body will naturally force the rest of the back to rest on the support surface.
The design of the BRUNAULT lumbar support, with its tapered tip, therefore directs the body into a degree of curvature that stimulates the disc fibers to tighten and strengthen.
If you sit in this ergonomic posture for 8 hours, for example, imagine how quickly the disc fibers can strengthen and correct lumbar sprains, sciatica and herniated discs.