Abstract: A chair shell of resilient material such as polypropylene comprises a back support 12 and a seat portion 14. The natural deformability of the back support 12 is modified by slits 22, 24 and holes 32, 34, 36 so that under pressure from the back of a sitter resting against the back support the support is resiliently deformed into a shape which, in vertical section, includes a convex curve positioned properly to support the sitter's spine in the lumbar region and which is horizontal in convex section. The deformability of seat 14 can be modified by slits 42, 44 and holes 42, 46, 48, 50, 54 to provide softer rear and front zones 44 and 52 to reduce the pressure on the ischial tuberosities and lower thighs of the sitter. The chair shell provides comfortable and orthopaedically desirable support while avoiding the need for thick upholstery. The undeformed state of the chair shell may be designed to allow the chairs to be easily stacked.

Abstract: A mattress for supporting the human body has shoulder-supporting and hip-supporting portions of less hardness than waist-supporting and foot-supporting portions. The hardnesses of the shoulder-supporting and hip-supporting portions are inter-related to the maximum hardness of the waist-supporting portions so that the mattress biases the spine of the user into a shape consisting of two concave curves separated by a convex curve, which gives a more comfortable mattress and has medical and orthopaedic advantages. The mattress can be used domestically, for specialist orthopaedic purposes and for general medical purposes.