Abstract: A mattress spring structure is provided with a strengthened central area thereon to provide greater support for a user's body lumbar region when received thereon. The strengthening is provided with a continuous frame that encircles coil springs over a major expanse of the central area, this frame being connected to first and last transverse rows of coils in the central area and extra central area transverse coil rows next adjacent the said first and last rows. The frame also connected to adjacently paired longitudinally arranged coils springs in the central area at both sides of the spring structure. High carbon steel of six or nine gauge is used for the frame.