Why does sportswear use synthetics, and what does it cost?

Put on a cycling jersey for a Saturday morning ride, or a running top for a lunchtime session, and if you've got the right kit you forget you're wearing it almost immediately.

On harder efforts it's moving sweat away from your skin before you've even noticed. The shorts are sitting where they should be without shifting or bunching. Good kit, at any pace and on any kind of outing, makes sport more comfortable and more enjoyable.

Contrast that with a cotton T-shirt from the back of a drawer - saturated within half an hour, cold and heavy against the skin on any descent, and liable to chafe somewhere awkward before long. The performance gap isn't marginal. It's the reason technical sportswear exists.

What's less often talked about is what that performance is made from. The fabrics in your running tee, your bib shorts, your waterproof shell - the overwhelming majority are derived from petrochemicals. Polyester, nylon, and elastane are all plastics, produced from crude oil and natural gas and spun into fibre. This is not a reason to get rid of your current kit, but I do think we should all be aware of the context that sits behind every purchase decision.

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Why synthetics dominate

Synthetic fibres exist because they work, and any honest account of the costs has to start from there.

Polyester is the backbone of most sportswear. It holds its shape under tension and repeated washing, and it has almost no moisture absorbency - water stays on the surface of the fibre rather than being absorbed into it, which is what allows it to be engineered to move sweat away from the skin. Nylon is stronger than polyester for its weight, more resistant to abrasion, and slightly softer to the touch, which is why it tends to appear in shorts, chamois liners, and anywhere subject to sustained friction. Elastane (sold under various brand names, most famously Lycra) provides the stretch and recovery that allows a cycling bib short to compress without restricting movement. It's typically present in small quantities in a fabric blend, but without it, most performance garments simply wouldn't function.¹

While progress is being made, what natural fibres cannot easily replicate is the combination of stretch, moisture management, and durability that endurance sport demands at the weights and thicknesses athletes actually want to wear. Wool absorbs moisture into the fibre itself rather than drawing it away from the skin, which can mean it feels wet during hard effort. Linen and cotton have no meaningful stretch. Natural fibres weren't optimised for the demands of performance sport but synthetic chemistry was, by design.

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What does it actually cost? The hidden journey of performance sports clothing

The environmental costs of synthetic sportswear are distributed across a garment's entire life, from the moment the raw material is extracted from the ground to the moment a jersey ends up in a landfill. Understanding that journey matters for any athlete who wants to make more informed choices, and it's the lens that shapes how this platform assesses brands.

The story begins with oil. Polyester starts its life as crude oil, which is refined and processed to produce PET (the same plastic used in drinks bottles) before being melted down and extruded into fibre.² This is an energy-intensive process, and because it starts with fossil fuel extraction, virgin polyester carries a real carbon cost before it's ever knitted into fabric. The bulk of the apparel industry's climate impact sits in what's called Scope 3 emissions (the emissions generated across a brand's entire supply chain, rather than just at its own premises), and fibre production is one of the largest pieces of that.³ Recycled polyester, typically made from post-consumer plastic bottles or industrial fibre waste, is a genuine improvement: it reduces the demand for virgin petroleum and generally produces fewer emissions per kilogram of fibre. But it isn't carbon neutral, and it doesn't change what the material fundamentally is. A garment made from recycled polyester is still a plastic garment.

Which matters, because of what happens every time you wash it. When synthetic fabrics go through a domestic washing machine, they shed microfibres - tiny fragments of plastic that pass through standard filters and wastewater treatment systems into rivers and oceans⁴. The science on this is still developing (see the explainer below), but what is well established is that synthetic microfibres are now found in deep ocean sediment, Arctic sea ice, fish tissue, and human blood. The practical angle is straightforward: washing kit after every session, as most active people do, means generating more of these wash cycles than the average person. The exposure scales with how often you train.

Then comes the end of the road. The vast majority of synthetic sportswear ends its life in landfill or incineration. Textile recycling infrastructure does exist, but blended fabrics (which is to say almost all technical sportswear) present a serious problem for it. When polyester and elastane are woven together in the same garment, separating them at end of life is often viewed as commercially impractical with current technology. Chemical recycling processes that can handle blends are in development, but they're not yet widely available or operating at scale.

This is where a gap opens up between brand messaging and material reality. Garments described as "recyclable" or marketed with take-back schemes are only as good as the infrastructure that receives them. A blended fabric jersey dropped into a take-back bin doesn't reliably become a new jersey; more often, it becomes landfill via a slightly longer route. That gap between what a label implies and what actually happens to the garment is one of the more significant credibility questions in the sector, and it's one this platform takes seriously.

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What alternatives exist

No material has fully solved this set of problems, but the alternatives are worth understanding.

Merino wool is the most technically credible natural option for endurance sportswear. It regulates temperature well, has genuine odour resistance from the natural properties of the fibre, and modern processing has improved its softness considerably compared to earlier generations. Its limitations are equally real - it's heavier than synthetics for equivalent warmth, less durable under sustained abrasion, and slower to dry when fully saturated. For base layers, lightweight mid-layers, and socks, it performs well. For anything requiring significant elastic recovery (a bib short, a form-fitting aero jersey), it can't do what synthetics do without blending in synthetic fibres, which reintroduces most of the same end-of-life problems.

Bio-based synthetics (fibres derived from plant sugars, agricultural waste, or other non-petroleum sources rather than crude oil) represent a genuinely interesting direction. Research into bio-based versions of polyester and nylon is active, and a small number of commercially available fabrics now incorporate these materials. The carbon chemistry is different from fossil-derived equivalents, but the performance profile and the end-of-life challenges are largely similar. This is early-stage territory; no bio-based synthetic has yet achieved mainstream adoption in performance sportswear at scale.

Recycled synthetics, as discussed above, are a real incremental improvement rather than a full solution. Worth seeking out, but worth treating as one factor in a broader assessment rather than a standalone answer.

The honest position is that no perfect material exists right now. The relevant question isn't whether any brand has found the answer (they haven't, and neither has anyone else) but whether brands are actively working on the problem with verifiable progress, rather than managing perception around a status quo.

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What this means when buying kit

The most sustainable choice, in a strict environmental sense, is to buy less - to get more use out of your existing kit, buy second-hand where possible, and only replace what genuinely needs replacing. But in practice, kit does wear out. Shorts that cause saddle sores need replacing. Wetsuits degrade. When something does need replacing, the question becomes how to make a more informed choice about what fills the gap.

A few markers carry genuine weight. Bluesign certification covers not just what a fabric is made from, but the conditions under which it was dyed and finished (chemical use, water consumption, worker safety) throughout the manufacturing process. OEKO-TEX STANDARD 100 tests finished products for harmful substances. Recycled content claims only mean something if they're independently verified against a standard such as the Recycled Claim Standard (RCS) or Global Recycled Standard (GRS), both administered by Textile Exchange. An unverified claim that a product is "made with recycled materials" should be closely scrutinised if it has no third party checking it.

DWR coatings (durable water repellent treatments applied to waterproof shells) are worth a specific mention. Historically, many of these relied on PFAS chemistry - a family of synthetic compounds often called "forever chemicals" because they don't break down in the environment.⁵ The industry is moving away from PFAS-based DWR at varying speeds, and it's a specific thing worth looking for when buying waterproof kit.

The difference between a recycled label and a verified material standard is, in practice, the difference between marketing and accountability. If you want to know which sports clothing brands are genuinely working to address these issues, and how far along they actually are, we've done the research so you don't have to. Head to our buying guides for the full picture.

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