Pressure Relief

When a contact point exceeds roughly 32 mmHg — the capillary closing pressure — blood flow to the skin and underlying tissue is restricted. The body responds by triggering a position change, which is why an unsuitable mattress produces restless, frequently interrupted sleep even when you do not remember waking.

In the lab we map peak pressure with a sensor mat across shoulder, hip and heel in each sleeping position. A well-matched surface keeps side-sleeping shoulder peaks under about 40 mmHg; a mismatched firm surface routinely reads 60 mmHg or higher at the same point.

Pressure relief comes from surface area, not softness alone. A conforming surface spreads the same body weight over more square inches, lowering the pressure at every point. That is why thick memory foam and pillow-top hybrids read well, and why thin, very soft foam over a hard core reads badly — it bottoms out.

Pressure relief and support are not opposites but they do trade off. The design problem every good mattress solves is delivering enough surface conformity at the shoulder and hip while still holding the pelvis in line.

Pressure relief is the mattress's ability to distribute body weight so no single contact point exceeds the roughly 32 mmHg at which capillary blood flow is restricted. Above that threshold the body triggers a position change — which is why a bed with poor pressure relief produces restless sleep even when nothing hurts.

Side sleepers need the most of it because shoulder and hip carry weight over small areas; back sleepers need far less. This is the single specification where 'softer is better' genuinely holds, right up to the point where spinal alignment fails.