Mattress firmness is not the goal by itself; the goal is choosing a firmness level that keeps the spine in a neutral position. For many people, medium-firm mattresses provide the best balance because they offer support while reducing pressure points. Very firm mattresses can increase shoulder and hip pressure—especially for side sleepers—leading to frequent awakenings and muscle tension. Very soft mattresses may allow the lower back to sink, disrupting spinal alignment. Body weight, sleep position, and existing pain complaints determine the ideal firmness: back sleepers often do well with medium-firm to firm support, while side sleepers typically benefit from medium-firm mattresses with effective comfort layers for the shoulders and hips. The safest approach is selecting a mattress with a trial period and strong durability/sagging warranty.