Response Time
How long a surface takes to return to its original shape after pressure is removed, measured in seconds. Determines how easy the bed is to move around on.
We time recovery by compressing the surface with a fixed load, releasing it, and recording the seconds until the surface returns to within a few millimetres of its uncompressed height. Latex returns in well under a second; traditional memory foam can take three to five.
Slow response produces the 'stuck in the bed' sensation. It is a feature for people who fall asleep in one position and stay there, and a serious annoyance for combination sleepers who change position a dozen times a night and have to fight the mattress each time.
Response time is temperature-sensitive in viscoelastic foams: the same mattress responds faster in a warm room and slower in a cold one, which is why some owners report their bed feeling firmer in winter.
Fast response usually comes bundled with more motion transfer, because the same springiness that lets you reposition easily also carries a partner's movement across the surface. Pocketed coils and high-ILD latex are the usual compromise.
Response time is how quickly a surface returns to shape after pressure lifts. Latex and polymer grids rebound almost instantly; traditional memory foam can take five to ten seconds. Nothing about sleep quality depends on this directly, but everything about how the bed feels to move on does.
Combination sleepers and anyone who is intimate on the mattress should weight response time heavily — slow-response foam resists position changes and creates the 'stuck' sensation. Strict side sleepers who settle in and stay put can ignore it entirely.
What This Means for Shoppers
If you change position often, or share a bed and get in and out at different times, choose latex, a hybrid, or a fast-response foam. Reserve slow-response memory foam for dedicated single-position sleepers.