Development of New Knit Fabric for Competitive Swimming: Friendly to Both Swimmers and the Environment

Competitive swimsuits continue to evolve through constant product development to meet the needs of users who want to “swim faster.” In particular, fabrics used in tech suits are treated with water-repellent finishes to reduce water resistance, while surface textures and processing methods are also carefully engineered.
However, when developing environmentally friendly products, the use of commonly adopted recycled polyester yarn and PFAS-free water-repellent ^*1 is said to increase costs and lower performance, making it difficult to achieve both required performance characteristics and environmental friendliness.
Therefore, through co-creation with Toray Industries, Inc ., Mizuno has developed a fabric that realizes greater environmental friendliness than ever before while achieving even lower resistance.

*1 Water-repellent that does not contain per- and polyfluoroalkyl substances (PFAS).

Key Development Points

Conventional competitive swimming fabrics achieved water repellency and low resistance by applying high-performance water-repellent treatment using fluorine-based agents to highly stretchable tricot fabric, combined with embossing special textures with raised and recessed structures on the fabric surface.
In developing this new fabric for competitive swimming, we established three key development focus areas: “skin friction drag of the fabric in water,” “water repellency,” which directly affects buoyancy, and “fabric stretchability” which directly impact comfort and ease of putting it on and taking it off. Additionally, we aimed to develop an environmentally friendly fabric while minimizing cost increases associated with using recycled polyester yarn and PFAS-free water-repellent.

Fabric Development through Co-creation with Toray Industries, Inc.

Co-creation Process

We began fabric development co-creation with Toray Industries, Inc., which possesses advanced fiber development capabilities.
Through preliminary research, we examined several knitting structures (herringbone patterns) to create special raised and recessed structures derived from biomimetics on the fabric surface. As a result, we achieved fine stripe-like raised and recessed surface structures on the fabric through combinations of different yarn thicknesses and various knitting structures. Furthermore, we explored optimal PFAS-free water-repellent formulations for this fabric, successfully developing and completing a new fabric that does not absorb water or become heavy even when submerged (*patent application filed).

Results Achieved

We conducted evaluation tests on the completed fabric to determine whether it met the three objectives set at the beginning of fabric development.
Result 1) Performance Enhancement
Through joint research with Associate Professor Kubota of Toyo University, we measured the skin friction drag of the fabric in water. Results showed that skin friction drag in water was reduced by approximately 2.6% compared to conventional fabric. Additionally, while using PFAS-free water-repellent, the fabric met Mizuno’s water repellency standards. The fabric also provides sufficient stretch, delivering excellent comfort in the final product.

Result 2) Environmental Friendliness
The new fabric eliminated the need for embossing processes in manufacturing. This reduced energy consumption and CO₂ emissions related to transportation and processing, creating an eco-friendly fabric.

Result 3) Production Cost Control and Lead Time Reduction
By eliminating the need for embossing, we absorbed the cost increases from using recycled polyester yarn and PFAS-free water-repellent, while simultaneously reducing fabric production time by approximately 6 weeks. This contributed to controlling excessive increases in fabric and product prices while achieving environmental friendliness.

We created a “fabric friendly to both swimmers and the environment” by reducing skin friction drag in the water and controlling total cost while maintaining environmental friendliness.

Awards and Recognition

The new fabric, named “Stream Fit Ribtex,” received high praise for “demonstrating how manufacturers can lead necessary social initiatives despite significant development constraints,” and was awarded the 2024 Good Design Award. Subsequently, the tech suit using “Stream Fit Ribtex” was named “GX・SONIC STREAM” and is scheduled for release in September 2025.

Mizuno has been committed to environmental conservation and promoting recycling for over 30 years. Moving forward, we will continue to create new products and materials that protect the global environment through co-creation with companies possessing innovative technologies, delivering them worldwide.