In good form

Somewhere between the first stretch and the last rep, most gym clothes give themselves away. The good ones you stop noticing; the rest start to make demands: a waistband that rolls, a seam that grumbles, a fabric that traps heat. We've all bought enough of the bad kind to know the tell: wear them a year and they're already asking to be replaced.

There's a plain reason for it: almost all activewear is plastic. Polyester, nylon and elastane are petroleum in a prettier form: cheap to spin and quick to stretch. I'm not about to swear off stretch altogether. After all, a legging with no give is barely a legging, and even the best pieces here keep a little. What matters is where a garment begins: start it from a natural or genuinely better fibre, skip the chemical finishes sold as ‘performance,’ and make it well enough to last.

Here are a few pieces we've found and loved.

Closest to the skin: Sports bra

Nothing you wear sits closer than a sports bra, which is why it's the piece I'd change first.

Cottsbury makes the natural-fibre answer: sports bras cut from 100% GOTS-certified organic cotton, built, in their words, for ‘yoga and beyond.’ The Organic Cotton Bra is the soft and breathable everyday option, while the Organic Cotton Medium Support Bra adds a little more hold for the days you're really moving.

Boody sits at the gentler end. Its Seamfree Padded Crop Bra, knitted from the brand’s signature bamboo viscose is a light-support, barely-there piece made for low-impact days, lounging, and layering. It earns its keep beyond the studio too: layer it under a slouchy blazer with wide trousers and it reads as an outfit, not sportswear. Bonus point: Boody is a certified B Corp and makes its pieces without intentionally added PFAS or chemical treatments, so the softness is the fabric itself, not a coating.

One thing to consider before you buy: organic cotton and bamboo are gentler and more breathable than synthetics, but they do hold a little more moisture, so they're happiest in yoga, light Pilates and everyday wear, rather than a hard run or a HIIT class.

The part that moves with you: Leggings

The legging is the hardest place to dodge synthetics, which is what makes the brands that manage it worth seeking out.

Boody’s High-Waisted Leggings lead with bamboo viscose and organic cotton, with four-way stretch that moves with you. The fibre is naturally moisture-wicking and temperature-regulating, which makes them the easy pair to reach for on ordinary days.

Baukjen, one of the highest-scoring B Corps in fashion, comes at it from the responsible-fabric side: its High Waist Comfort Leggings are the everyday workhorse, while the Kimberley Leggings bring flare for the eye and pockets for the everyday.

And if your practice lives on the mat, Cottsbury’s Organic Cotton Yoga Tights, three-quarter length with a pocket, carry the same GOTS-cotton logic all the way to the ankle.

For the hard sessions

For a sweaty spin class, a real run or anything that leaves you dripping, natural fibres aren't always the right choice, as they hold moisture. This is the one place I'll happily reach for a synthetic, as long as it's a recycled one, made to last.

Girlfriend Collective has built its whole range on exactly that: activewear spun from recycled plastic. By the brand's count, around twenty-five old water bottles go into a single pair of leggings, and everything is sewn in a fair-labour, SA8000-certified factory, in a size range (XXS to 6XL) most performance brands still can't be bothered with.

The Compressive High-Rise Legging is the cult one: dense, squat-proof and genuinely supportive, so pair it with the Paloma Bra for the high-impact days. It's still plastic, but it's plastic rescued once already, and built to be worn for years rather than shed through a single season. When you truly need performance, that's the kinder version of it.

For the walk home: Athleisure

Most sportswear never sees a gym, and there's no shame in that; some of my most-worn ‘activewear’ has only ever done a long Saturday walk. Athleisure is where a good sustainable piece really earns its keep, because you'll live in it.

Encircled has quietly made this its craft. The label works out of Canada, holds B Corp certification, and builds around TENCEL lyocell drawn from wood pulp. The Dressy Sweatpant lives up to its unlikely name: a trouser's line with a sweatpant's ease, as at home on a studio floor as on the six o'clock train, and the Sojourn Half-Zip is the pull-on layer I'd pack first for a weekend. For the dressy sweatpant, I’d style it the way you would a real trouser: a fine knit tucked loosely at the front, a loafer or a clean sneaker, and a structured bag to stop the whole thing tipping into loungewear.

Baukjen’s Bergan Organic Cotton Wide-Leg Joggers take the loose route in pure organic cotton, and for the softest way to cool down. And for the softest way to cool down, Boody’s bamboo Sweater and matching Sweat Pants are hard to beat.

A final word

The cheap synthetic set flatters you at the till and nowhere after it. Spend a little more on the natural or better-made version and it pays you back in the currency that counts: comfort against working skin, an easy life in the wash, and the quality to see out the hundreds of workouts you'll genuinely give it. Fewer pieces, more miles in each. For clothes made to move, there's no better result than that.