Compliant backrest

A backrest comprising:

• a primary frame member comprising a pair of laterally spaced first side members, a first upper member extending laterally between and connecting the first side members, and a first cross member longitudinally spaced below the first upper member, wherein the first cross member extends laterally between and connects the first side members, wherein the first side members, first upper member and first cross member define a first central opening, and wherein the first side members each have a lower portion extending below the first cross member, wherein the lower portions are connected to a forwardly extending support member, wherein the lower portions and first cross member partially define a second central opening positioned below the first central opening;
• a secondary frame member coupled to the primary frame member, wherein the second frame member comprises a pair of laterally-spaced second side members overlapping the first side members of the primary frame member, a second upper member overlapping the first upper member of the primary frame member, and a second cross member overlapping the first cross member of the primary frame member, wherein the second side members, second upper member and second cross member define a third central opening aligned with the first central opening, and wherein the second cross member is the lowermost portion of the secondary frame member;
• and
• a flexible shell comprising opposite sides coupled to the second upright members and upper and lower portions coupled to the second upper member and the second cross member respectively, wherein the shell covers the first central opening, and wherein at least a portion of the second central opening is not covered by the shell.