Firm mattresses, which usually fall within the 8-10/10 range on the firmness scale. These beds rarely employ soft or plush materials in their comfort layers; instead, they insert a thin layer of soft foam atop high-density polyfoam or springs. Firm mattresses can be highly supportive for stomach sleepers and heavier people.

On a firm mattress, every part of your body should be lifted squarely on the mattress with plenty of push back.