Medical and ergonomic studies showed the important of a correct lumbar curve well conformed (fig.1) for an office chair of for a seat used driving car, truck …(it will improve the vertical vibration absorption that the column has during the drive).

The ideal position of the lumbar curveshould be adjustable between 17cm and 28cm from the seat floor and the curve should arrive to 4- 5 cm.

The back seat inclination should be at least 100°. These measurements should be adapt to the different peoplelordosis curve.

During seated the physiological lumbar lordosis curve is cancelled increasing the vertebraldisc pressurestressing the structure (fig. 2)