Seating structure with a contoured flexible backrest

A seating structure comprises a backrest member comprising a shell having a front body-facing surface and comprising a central, spine region and side regions positioned on opposite sides of said spine region., The backrest member has a plurality of openings formed in at least one of upper, middle and lower portions of said side regions on opposite sides of said spine region, wherein said spine region has a greater rigidity than said side regions, said shell defining upper, lower and side edges of said backrest member wherein said at least some of said openings comprise vertically spaced laterally elongated portions connected with a thinner longitudinal portion, and wherein at least some of said openings have one of an I-beam shape or an hour-glass shape. An auxiliary support member is moveably coupled to said backrest member, said auxiliary support member moveable in front of said front body-facing surface of said backrest member. A body supporting substrate is disposed along said front body-facing surface of said backrest member and covering said auxiliary support member. 11537252 1 (GHMatters)P91413.AU.3