What gives elastane its recoil
Elastane is a synthetic polymer—a material made of long, linked molecules. Its chains contain flexible sections that sit in loose, curled shapes when the fabric is relaxed. Stretching straightens and aligns those sections; when the pull ends, the chains tend to curl back toward their less-stretched arrangement.
The chains also contain firmer regions that help keep them from simply sliding past one another. That combination—flexible stretches anchored by more stable parts—lets the fiber extend substantially and then recover. The “spring” is molecular, not a tiny metal coil inside the thread.
Why leggings are a blend
A garment usually combines elastane with fibers such as nylon or polyester. Those other fibers supply much of the fabric’s surface and structure, while a relatively small amount of elastane can make the whole knit give with the body and return afterward. How the yarns are combined and the fabric is knitted also affect how stretchy and supportive the garment feels.
Recovery is not unlimited. Repeated strain and exposure to harsh conditions can gradually weaken elastic fibers, so a garment may become less snug over time. The practical payoff is that a fabric can move with a bent knee or deep lunge—and, as long as its elastic network remains healthy, settle back instead of staying bagged out.
