Here’s a small life dilemma for you: athleisure. It’s the new shoulder pads, a sartorial norm in which structure and adornment have given way to slouch and utility. Basically, if you go out to lunch looking as if you could happily sprint 15 miles home, and defeat a foe with kick-boxing on the way, that’s good. But don’t mistake it for active wear. Active wear is when you dress for the gym, but your true intentions are coffee and a muffin. This is delusional and inauthentic, the stuff of parodic videos, the stain of that already much-derided class, the Yummy Mummy.

The problem is, athleisure and active wear are really hard to tell apart. It mostly comes down to smelliness. As Jodi Kerschl, who founded Bellum (beautiful sports stuff, mainly for runners), tells me, the technology of sweat is now in a new league. “Some of the older polyester fabrics, that mesh look, were absolutely awful. Even after you’d washed it, you could still smell every odour. Performance fabrics now breathe really well.”

Today, you could do a boot camp and smell premium afterwards. In extreme temperatures (running, doing hot yoga), you can genuinely tell the difference between a bra top made this year and one made in 2016. You will be too hot in either, of course; but in the older one, you’ll also be sticky, maybe even sore, and definitely unhappy (this will play havoc with finding your inner stillness).

The other big development is compression fabric, which slimlines the silhouette, as well as supposedly helping with muscle soreness and fatigue. You can do a lot in saggy leggings except walk around in public, when it all looks a bit pyjama-y. You’ll notice a lot of panelling in the modern legging: it has a performance element, in that it’s often a hyper-breathable fabric, but it also plays a trick on the eye and makes it look more like a trouser and less like a costume you stole from a superhero. Perfectionism has migrated from elite athletics, so that everything matters, from the position of each seam to the varying breathability of each panel; whether or not it will make the average gym-goer faster, who knows? But it certainly works aesthetically.

Ultimately, when it comes to buying clothes you want to do actual sport in, there are some dos and don’ts. Do buy proper sports trainers, even if they’re too bulky to pass as fashionable. Do invest in an actual tight sports bra, and do consider a proper pair of compression leggings (ideally high-waisted for comfort and support). If you’re planning on doing medium-intensity exercise, such as Zumba, then those roomy, relaxed yoga pants are a very good all-purpose purchase.

Don’t bother with any of that thick, meshy, panelled stuff that looks fairly sporty, but is actually horrendously sweaty. Don’t buy high-street “sports casual” clothes – vests, or leggings, say – that don’t work as either casual or for actual sport. Don’t buy those shiny satin joggers currently all over the high street, unless they’re for a party. In which case, go, dance and be sweaty in style.

What I learned

If you invest in only one bit of proper technical wear, make it your underwear. Chafing at the crotch or chest is no joke.