Next-Generation Sustainable Sportswear: Engineering Performance Through Knit Structures and Material Selection

Growing environmental and systemic challenges in the sportswear industry call for a shift toward function-led, sustainable design engineering, yet the potential of weft flat-bed knitting technology, which enables precise stitch control and compatibility with sustainable yarn systems, remains underexplored. This study examines how three flat-bed stitch structures (interlock, ripple, and pointelle) interact with five yarn systems, including recycled polyester, merino wool, merino–Sorona blends, and PLA, to influence thermophysiological and mechanical performance when compared with commercial circular-knitted fabrics. The results demonstrate that fiber–stitch interactions govern fabric performance, with porosity, fiber composition, and stitch architecture collectively influencing breathability, moisture management, thermal response, and mechanical behavior. Distinct moisture-management behaviors were observed between transport-dominated synthetic fibers and absorption-driven natural fibers, exemplified by merino ripple’s saturation time (454.2 ± 17.4 s) exceeding that of PLA pointelle (85.5 ± 5.4 s) by approximately 431%. These findings reveal distinct moisture-management behaviors among the evaluated fiber systems, pointing to potential alternative approaches for sportswear design that merit further investigation. Overall, the results demonstrate the potential of weft flat-bed knitting technology as a design-engineering tool for developing function-driven sustainable sportswear systems.