A spring core is provided that includes a plurality of coil springs having an upper portion and a lower portion that collectively define an interior cavity. The spring core further includes a continuous upper fabric layer that covers each coil spring and defines a recess in the interior cavity of each coil spring. A cushioning layer is positioned atop the continuous upper fabric layer and extends into the recess in the interior cavity of each coil spring. A mattress assembly is further provided that includes the spring core, an upper body supporting layer, and a lower foundation layer. Methods of producing a spring core are further provided.