Abstract: A bed assembly (1) for altering the position of a person supported thereon, includes a longitudinal support frame (5) having a support surface (23) for a person and a longitudinal cradle means (4) extending over the support surface. The cradle has a recess (10) extending along side portions of the cradle in the longitudinal direction. The recesses are adapted to receive and engage cradle support engaging means (7, 7a). These means are mounted to the support frame in close relation to the recess and adapted to be extendable and retractable in engaging relation within said recess so as to promote a change in configuration of the cradle. A first actuator (3) is disposed beneath the support frame and coupled to the engaging means for extending or retracting the engaging means. In a first condition the actuator causes the engaging means to extend towards and be received by the recess, causing the cradle means to move between a position of rest and a concave configuration about the central longitudinal axis.