Adjustable backrest (10) comprises upper, middle and lower support units (12, 14, 16) mounted between upper and lower frame sections (18, 20) of a chair (not shown). Each support unit (12, 14, 16) comprises a first part (30) and a second part (32) which is releasably mounted on the first part (30), e.g. with bolts (33). The second part (32) comprises a plurality of members (34), joined together in series to define a spinal support surface (36) with a substantially arcuate profile. The spinal support surface (36) extends to each lateral side of the first part (30), and is configured to provide lateral support to a users spine when resting against the backrest (10). Adjacent pairs of members (34) are each joined together with a lockable hinge arrangement (40) for preventing pivotal movement of one member (34) relative to the other member (34) about respective pivot axis (42) when locked, whilst allowing pivotal movement of one member relative to the other about respective pivot axis (42) when unlocked. Pivotal movement of the members (34) about their respective pivot axes (42) when their respective hinge arrangements (40) are unlocked allows the substantially arcuate profile of the spinal support surface (36) to be adjusted to fit snugly against a users spine.La présente invention concerne un dossier réglable (10) comprenant des unités (12, 14, 16), supérieure, intermédiaire et inférieure, de support, lesdites unités étant montées entre des sections (18, 20), supérieure et inférieure, de châssis dune chaise (non représentée). Chaque unité (12, 14, 16) de support comprend une première partie (30) et une seconde partie (32) qui est montée amovible sur la première partie (30), par exemple avec des boulons (33). La seconde partie (32) comprend une pluralité déléments (34), reliés les uns aux autres en série pour définir une surface (36) de support de la colonne vertébrale ayant un profil sensiblement arqué. La surface (36) de support de la colonne vertébrale sétend de cha
