Abstract: An automobile seat backrest includes an adjustable lumbar support assembly for selectively applying pressure to the lower area of a seated occupant's back. The backrest portion has a structural frame and a wire mesh within the frame for supporting a foam cushion. A cover envelopes the frame, wire mesh and cushion. First and second cranks are moveably supported on the wire mesh within the cover of the backrest portion. Cantilever arms extend from the respective first and second cranks to carry corresponding first and second applicator pads. A manual actuator causes the applicator pads to move in a synchronized fashion toward respective extended positions applying outward pressure to the cover. The manual actuator includes a twist knob which controls a worm gear, and a drum having gear teeth that mesh with the worm gear. A conduit extends from the actuator to the first crank, and a core element, slidably disposed within the conduit, interconnects the twist knob and the second crank.