The Problem Nobody in the Fitness Industry Wants to Talk About
Most gym wear is plastic. Not partly plastic, predominantly plastic. Leggings, sports bras, base layers: the vast majority are made from polyester, nylon, or spandex. All synthetic fibres. All derived from petrochemicals. All designed to last centuries in landfill, and all shedding thousands of microplastic particles every time you wash them.
The British Antarctic Survey has detected microplastics in some of the most remote ocean depths on earth. A significant proportion come from synthetic textiles. Every wash cycle from a standard pair of gym leggings releases an estimated 700,000 microfibres into the water system. They pass through most wastewater treatment facilities unfiltered, entering rivers, oceans, and the food chain.
This is the quiet cost of fast-fashion activewear. And it's why, when people start looking for sustainable gym wear, the need is genuinely urgent, not just a lifestyle preference.
But navigating the market is harder than it should be. Because the word 'sustainable' has been stretched to cover everything from recycled plastic bottles to bamboo blends treated with harsh chemical softeners. This guide cuts through it.
What Actually Makes Gym Wear Sustainable?
1. The fibre not just the marketing language
The single biggest factor in a garment's environmental impact is what it's made from. Natural or plant-derived fibres, cotton, lyocell, Tencel are biodegradable at end of life. Synthetic fibres, polyester, nylon, elastane are not.
This matters enormously. A garment made from Tencel lyocell (the plant derived fibre used in both the Elara leggings and Flo t-shirt) will biodegrade through natural biological processes when it's eventually retired. A polyester equivalent will persist in the environment for up to 200 years.
Be wary of 'recycled polyester' as a sustainability claim. It does reduce the demand for virgin plastic, which is a positive but it doesn't solve the microplastics problem, and the garment still can't biodegrade at end of life. It's a partial improvement, not a solution.
2. Third-party certifications: The ones that actually mean something
Certifications are the shortcut past greenwashing. But not all carry equal weight. Here's what to look for:
- OEKO-TEX Standard 100: Tests every component of the fabric (thread, dyes, fastenings) for harmful substances. An OEKO-TEX certified garment has been independently verified to contain no substances harmful to human health.
- Cradle to Cradle (C2C) Certified: A more comprehensive standard that evaluates material health, recyclability, use of renewable energy in production, water stewardship, and fair treatment of people in the supply chain. A C2C Gold certification is one of the most rigorous credentials in sustainable textile manufacturing.
- GOTS (Global Organic Textile Standard): Relevant primarily for cotton and other organic fibres. Certifies organic farming practices and responsible processing.
- Bluesign: Focuses on chemical safety and responsible resource use in the dyeing and finishing process.
Both the Elara leggings and Flo t-shirt hold OEKO-TEX Standard 100 and Cradle to Cradle Certified Gold, two of the most meaningful independent credentials in the industry.
3. How and where it's made
Sustainable materials can still be produced in exploitative conditions. Where a garment is made and who makes it, matters as much as what it's made from.
UK manufacturing offers shorter supply chains, greater transparency, and the assurance of UK employment law. When a brand tells you a garment is manufactured in the UK by skilled machinists, that's a meaningful commitment, not a marketing phrase.
Pay attention to energy sources too. Fabric woven using 100% renewable energy has a materially lower carbon footprint than the same fabric produced on a coal-powered grid.
4. What happens to it at end of life
A truly circular garment returns safely to nature when it's worn out. This requires the entire product, not just the outer fabric, but the trims, labels, sewing threads, and elastics, to be biodegradable. It's a detail most brands overlook entirely.
The Greenwashing Traps to Avoid
The sustainable apparel market has grown fast enough to attract plenty of opportunists. Here are the claims that should prompt a second look:
- 'Eco-friendly' with no certification. Unverified claims cost nothing to make. If there's no independent certification backing the claim, treat it as marketing copy, not fact.
- 'Made from recycled materials' without clarity on end-of-life. Recycled polyester is still polyester. It still sheds microplastics. It still won't biodegrade. It's better than virgin plastic but it's not a closed loop.
- 'Organic' fabric with conventional dyes. A fabric can be grown organically and then treated with chemical dyes and synthetic finishing agents that introduce toxins back into the product and into you. Check whether natural dyes are used throughout.
- 'Sustainable packaging' as the headline claim. Recyclable packaging is a good thing — but it doesn't compensate for a garment made from petrochemical fibres with no end-of-life plan.
- Vague supply chain language. 'Ethically sourced' and 'responsibly made' mean nothing without evidence. Look for named certifications, named manufacturing locations, and specific commitments.
A Quick Checklist: 5 Questions Before You Buy
Before adding sustainable gym wear to your basket, run through these:
- What fibre is it made from and will it biodegrade at end of life?
- Does it carry independent third-party certifications (not just brand claims)?
- Where is it manufactured, and under what conditions?
- Are natural dyes used, or synthetic chemical dyes?
- Is the whole garment sustainable including trims, labels, and threads or just the main fabric?
What Good Looks Like
The honest answer is that genuinely sustainable gym wear is harder to produce and more expensive to do properly. That's the reality. But 'harder' is not the same as 'impossible'.
At 9 Elephants, every design decision starts from the same two questions: will this serve its purpose without harming the planet or human health? And are the people behind its production being treated fairly? From Swiss Tencel fabric produced on 100% renewable energy, to natural dyes, biodegradable trims and threads, and UK manufacturing the brief was to do it properly or not at all.
If you're building a gym kit that you can feel as good about as you feel in it, that's the standard worth holding out for.