A bed comprises a frame 34 with at least one orientation adjustable section (44, 46, 48), a mattress 58 supported by the frame and having at least one A bladder and at least one B bladder. The bladders are inflatable and deflatable cut of phase with each other in coordination with at least one of a) issuance of a command for the frame section to change orientation and b) an actual change in orientation of the frame Also described is an associated method for operating an occupant support at least part of which its orientation relative to other parts of the occupant support. The method comprises providing, in response to a change of orientation of the orientation adjustable part, a relatively lower occupant/support interface pressure (OSIP) at a location A and a higher OSIP at a location B followed by providing a relatively higher OSIP at the location A and a relatively lower OSIP at the location B.
