According to the Wall Street Journal, the sale of yogawear in America went up by 45 per cent last year. This despite the fact that the increase in the number of Americans actually doing yoga was a mere 4.5 per cent.

Take those two statistics together and what have you got? You've got a lot of women in comfortable pants, is what you've got. The trackie revolution is well under way among our American sisters. They're wearing their comfy pants wherever the day takes them; to work, to school, to coffee, maybe even to an actual yoga class on special occasions.

It's estimated the US market for fitness gear in general has been growing by 5 per cent on average for the past five years. It'll be worth US$100 billion ($1.2 billion) by 2020, is the prediction. That's a lot of trackie-dacks, and we're not even including the high-end versions.

Kanye reckons he invented the leather jogging pant well before Celine made one, meanwhile Alexander Wang has been doing them for ages. You'll pay US$200 for any one of those, minimum. But women are prepared to drop mad money on sweatpants nowadays. I should know. I'm one of them.


My pants aren't Alexander Wang, but a fancy enough American label. I scored them in TK Maxx for a price rather lower than the ridiculous amount you'd pay retail. They're the kind you see Jennifer Aniston coming out of the gym in: your basic, 3/4 length, grey marl trackies with a drawstring waist.

Now I know why Jennifer Aniston always looks so happy in photos. She wears a lot of sweatpants, and sweatpants are brilliant. Not only are they comfortable, they make you feel virtuous. Weirdly, happily, energetically virtuous. Like you've just had the best workout, even though you've done nothing.

You put them on, and there's an instant hit from it. Tying the drawstring around your hips, you can already feel your lungs filling with fresh oxygen, your feet flying over the pavement. Who knew you can get an endorphin buzz from getting dressed for exercise without actually having to do any?

The American apparel industry has a word for this sort of dressing. It's called "athleisure". Throwing on a pair of gym pants to meet a friend for coffee, basically. I have another word for it: "magic." I can't really explain how it works, nor do I want to, but the advantages of having exercise gear that obviates the need for actual exercise are manifold.

I put them on in the morning and I can feel myself getting fitter. I feel alive and energised, and aglow with good blood flow. Then I go downstairs, and spend four hours reading and eating gorgonzola. This, my friends, is athleisure. Welcome to the future of fashion. Thank God for the drawstring waists - we're going to need them.