You’ll see sustainable fibers like recycled polyester, Tencel, and organic cotton increasingly match traditional synthetics for running gear, offering moisture management, stretch, and durability while cutting reliance on virgin resources. Expect better dyeing, odor control, and circular options as costs fall and certifications improve, though supply-chain complexity and higher upfront prices remain. Designers will emphasize repairable, long-lasting construction and take-back programs. Keep going to explore specific fibers, trade-offs, and practical sourcing steps.