An ergonomically designed seating apparatus comprising: a seat comprising: a seat frame adapted to be secured to a chassis; a seat support pivotally connected to the seat frame such that the seat support is capable of pivotal tilting about a first transverse horizontal axis relative to the seat frame; at least one first resilient member positioned between the seat frame and the seat support permitting resilient relative pivotal tilting therebetween; and a backrest comprising: a back frame adapted to be secured to the chassis, the back frame comprising two parallel bars; a lumbar support connected to the back frame at each of the two parallel bars; a back support pivotally connected to the lumbar support such that the back support is capable of pivotal tilting about a second transverse horizontal axis relative to the back frame, the two parallel bars aligning parallel to and on either side of the second transverse horizontal axis such that the second transverse horizontal axis is between the two parallel bars and said back support extends above the two parallel bars; at least one second resilient member positioned along surfaces of the lumbar support and the back support permitting resilient relative pivotal tilting therebetween; wherein the chassis is part of a wheelchair frame; and said back frame and said seat frame are connected to and removable from the wheelchair frame having at least three wheels, wherein a position of the second transverse horizontal axis is adjustable relative to the wheelchair frame from front to back. a seat frame adapted to be secured to a chassis; a seat support pivotally connected to the seat frame such that the seat support is capable of pivotal tilting about a first transverse horizontal axis relative to the seat frame; at least one first resilient member positioned between the seat frame and the seat support permitting resilient relative pivotal tilting therebetween; and a backrest comprising: a back frame adapted to be secured to the chassis, the back frame comprising two parallel bars; a lumbar support connected to the back frame at each of the two parallel bars; a back support pivotally connected to the lumbar support such that the back support is capable of pivotal tilting about a second transverse horizontal axis relative to the back frame, the two parallel bars aligning parallel to and on either side of the second transverse horizontal axis such that the second transverse horizontal axis is between the two parallel bars and said back support extends above the two parallel bars; at least one second resilient member positioned along surfaces of the lumbar support and the back support permitting resilient relative pivotal tilting therebetween; wherein the chassis is part of a wheelchair frame; and said back frame and said seat frame are connected to and removable from the wheelchair frame having at least three wheels, wherein a position of the second transverse horizontal axis is adjustable relative to the wheelchair frame from front to back. a back frame adapted to be secured to the chassis, the back frame comprising two parallel bars; a lumbar support connected to the back frame at each of the two parallel bars; a back support pivotally connected to the lumbar support such that the back support is capable of pivotal tilting about a second transverse horizontal axis relative to the back frame, the two parallel bars aligning parallel to and on either side of the second transverse horizontal axis such that the second transverse horizontal axis is between the two parallel bars and said back support extends above the two parallel bars; at least one second resilient member positioned along surfaces of the lumbar support and the back support permitting resilient relative pivotal tilting therebetween; wherein the chassis is part of a wheelchair frame; and said back frame and said seat frame are connected to and removable from the wheelchair frame having at least three wheels, wherein a position of the second transverse horizontal axis is adjustable relative to the wheelchair frame from front to back.