If you'd have told me 18 months ago that a pair of £510 velvet-trimmed Haider Ackermann track pants would one day sit at the top of my wish list, I'd probably have shot you my steeliest side-eye. If you'd also said my justification for such a fantasy purchase would be, 'They're great for both work and weekends!' I would have told you to stop being so silly.

But here I am now, poring over a photo of Rosie Huntington-Whiteley wearing a similar £810 pair by Chloé as she strolls through LAX Airport.

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Rosie Huntington-Whiteley wearing rainbow-trimmed Chloé track pants

She's channelling what we fashion writers rather uninventively call the 'model off-duty' look: her outfit, which also includes a grey tee and black blazer, combines comfort and style in equal measure. She is, of course, in no way 'off duty' – with her image being her fortune, she never truly is, especially at the paparazzi battleground that is an airport. Proof: she's also wearing 5in heels.

Even though I know all of the above, I'm still hooked on the idea of more frequently wearing the kinds of clothing that were once limited to Saturday dog walks in the park. That's largely thanks to the runways, where sweatshirts (Burberry, Hood By Air, DKNY – the list goes on) and baggy denim (Balenciaga, Alexander Wang) rules.

I've even contemplated creating a DIY version of my own track pants courtesy of John Lewis' haberdashery department. This is the perfect example of the power behind those two little words: off duty. Initially a trend, it's now a movement. It no longer pertains to our weekend wardrobes – it's impacting how we dress for work. But why, and what does this mean for our actual off-duty wardrobes?

'We're dressing more comfortably because we're seeking ease in our hectic lives.'

'We're dressing more comfortably because we're seeking ease in our hectic lives,' says Tamu McPherson, Founder of street-style website All The Pretty Birds. 'Our productivity demands are so much higher and life is more dynamic than it has ever been, so it necessitates less-formal clothes.'

It's true; according to a study by the Trade Union Congress, the average UK working week now stands at 43.6 hours compared with a European average of 40.3 hours, while the number of people working excessive hours (more than 48 hours a week) has risen by 15% since 2010.

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Jan-Michel Quammie wearing Palace joggers at Milan Fashion Week

The most recent British Social Attitudes Survey reveals we're experiencing more work-related stress than ever, but conversely, those in professional jobs have more freedom and flexibility at work than they did a decade ago, suggesting we're happy to work longer and harder for more autonomy. It's little surprise then, that as our work life has percolated into our home life, we've reassessed the role our clothes play in helping us deal with it. For many of us, particularly those in the creative industries, this has blurred the line between workwear and weekend wear.

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Edie Campbell wearing a Chloé tracksuit during Paris Fashion Week

'I remember a few years ago, the first time I saw somebody wearing trainers at work. I thought, "She looks really efficient,"' says Lisa Aiken, Net-A-Porter's Retail Fashion Director. 'When you are comfortable, I believe you are more effective.'

Kate Unsworth, Founder of wearable tech startup Vinaya, says she can't remember the last time she bought clothing just for work. 'Everything has to be adaptable to my lifestyle. If I'm on a nine-hour flight, having meetings with investors or going to dinner with friends, I don't want to have to think about whether my clothes are going to be able to keep up with my day.'

Having become aware that we're now seeking multipurpose pieces that represent our busy lives but with comfort at the core, designers and brands are upping their off-duty game – and we're playing along. 'Previously, the off-duty wardrobe was an afterthought, but nowadays women are using them to express their personalities,' Aiken says.

'They're able to have more fun styling the pieces, so they are certainly willing to invest in it more.'

As such, the sweatshirt – once a lesser-thought of essential – has become a luxe statement piece we're willing to splash out on, whether it's a signature Bella Freud knit at just under £300 or an intarsia tiger number by Gucci for a £700 price tag. And hoodies continue to rise in popularity: 'Off-White and Vêtements are leading the way,' says Aiken.

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Miroslava Duma

So if off-duty dressing has taken over our working week, what do we actually wear when we're, you know, off duty? Natalie Kingham, Buying Director of matchesfashion.com, recommends the high-low approach and investing in great outerwear. 'I really like athleisure with a camel coat over the top. Designers are doing more cargo and army jackets, which are good for transseasonal off-duty. The length, shape, fabric and colour go with everything.'

Of course, this change is not simply down to our shift in work-life balance. It's rooted in how fashion has progressed over the last decade.

When Alexander Wang, a Parsons School Of Design dropout, arrived on the scene in 2006, he introduced an antidote to the trend treadmill: inconsequential, slightly worn everyday items such as the oversized T-shirt and moth-eaten jumper repurposed with a 'don't give a damn' attitude. Thus, contemporary off-duty dressing was born.

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LAUNCHMETRICS SPOTLIGHT
Dree Hemingway

Of course, Wang didn't invent casual dressing. 'People have always changed into casual stuff when they get home – it marks the transition between work and downtime,' notes Kate Finnigan, The Telegraph's Fashion Features Director. But what he did do was take it from being something of an afterthought to the catwalk and, more importantly, beyond. If a trend is a holiday romance – you meet, you flirt, you say your goodbyes and, years later, you look back with a mix of nostalgia and 'What was I thinking?' – what Wang did was plant the seed for a love affair worthy of a Nicholas Sparks novel.

Ten years on, off-duty dressing's roots are anchored and its influence none more apparent. But it wouldn't be fashion if things didn't progress – again, we have Wang to thank for that. In 2014, he used his H&M collaboration to bring athleisure to the masses. 'I live in gym clothes. When you go out on the street, it's the uniform now,' he told The New York Times when it launched, adding a major 'but': 'I'm not an athlete.'

'As our work life has percolated into our home life, we've reassessed the role our clothes play in helping us deal with it.'

It was a sensibility that struck a chord with women everywhere. Wearing workout clothes in our time off seemed like what we were searching for; the next step in 'off duty', it also went hand-in-hand with the way in which our attitude to health was changing. 'Wellness culture definitely influenced a shift to athleisure in our downtime,' says McPherson. 'It's so important for me to work out, but I don't have time to change for whatever else I have going on that day.'

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Linda Tol wearing Adidas three-stripe joggers

It may not have been innovative, but as he did with his simple-but-bold 'off-duty' look years ago, Wang lit the touch paper for the trend to influence other designers. And it's still going strong.

Wearing gym clothes – something that not so long ago may have seemed lazy – now allows us to tell the world: 'I'm busy but I'm in control and take care of myself.' In an era where our brains are bombarded with never-ending notifications, maybe we need our clothes to reflect our increasingly hectic lives. It's also worth noting that 'off duty' and athleisure are two movements that have undoubtedly been strengthened by social media. Not just because it has exposed us to thousands of 'influencers' who are showing us how to nail it, but also because Instagram has altered our perception of how successful women dress now.

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Veronika Heilbrunner

We're presented with the likes of Leandra Medine and Chiara Ferragni, both of whom preside over growing media empires in jeans and tees. 'The suit is amazing, but you don't have to wear one to prove you belong at that table. You wear what you want,' says McPherson. Off duty really is at its most powerful right now.

But in a sea of athleisure and built-for-comfort clothes, how can we maintain our individuality and avoid becoming too casual?

'My advice is to always have one element that is personal to you,' says Aiken. 'I'll always have my Hermès watch and multiple rings on no matter what I'm wearing.' Meanwhile, I've found an alternative to my dream tracksuit bottoms that won't leave me eating soup for six months: Adidas Originals' premium three-stripe cigarette trousers. Athleisure with a bit of tailoring. I think we're going to be very happy.


This feature originally appeared in the November 2016 issue of ELLE.