Generally speaking, the most effective mattresses for posture are those that provide enough support without making pressure points worse. The most common sleeping position is on one’s side, and the chart above illustrates the appropriate level of mattress firmness
for side sleepers. You’ll find that there’s a wide range of ideal mattress firmness for various body shapes. It is true that a softer mattress is more comfortable for individuals of a smaller stature, but it might actually exacerbate posture problems for those of a bigger build. You should choose a mattress firmness that is comfortable for your sleeping posture and body type.