Ergonomically designed chair

An ergonomically designed chair comprising a rigidly mounted seat, a back rest integrally joined to the seat and a shoulder rest integrally joined to the upper end of the back rest, the profile of the central region of the back rest substantially matching the curve of the human spine, wherein the back rest is joined to the seat by means of a portion of the back rest which fits into a region at the rear center of the seat and at least said portion of the back rest is provided with stiffening means which impart to the back rest a substantially stiff form up to about the level of the sixth lumbar vertebra of the chair occupant, thus ensuring a continuous transition from the chair seat to the back rest, but allow the back rest an increasingly greater flexibility from said level upwards with the result that the upper part of the back rest bends backwards when the occupant leans back, and wherein the upper end of the back rest is joined to the shoulder rest via a bracing corrugation in order to ensure that the chair profile in the region of the occupant's shoulders is a smooth curve matching that of the occupant's spine.