Every week, we bring you the best shoppable fashion and lifestyle stories from the editors at InStyle.com, including this exploration of the athleisure trend  in fashion.
Welcome to Now You Know, Eric Wilson 's column that will help you become a fashion know-it-all in one quick read. Each week, he takes a look at an endearing fashion influence and why it's relevant right now. Enjoy!
The latest buzzword in fashion is "athleisure," one of those made-up terms that are so ridiculously nonsensical as to be perfectly descriptive. That is, designers and retailers are obsessed with clothes that fit a somewhat broad category of being appropriate for either athletic or leisure pursuits, or both. We're talking about anything from designer leggings of the Lululemon  variety to cashmere sweats to layering pieces to absurdly fancy (and expensive) gym clothes. This is a topic I explored in depth in the Look Smart column of the August issue of InStyle  (on newsstands now) and took note of the trend of retailers opening new sport and athleisure stores—including Without Walls from Urban Outfitters  and Lou & Grey, the popular loungewear collection from Loft—in recent months.
Looking at the number of companies that have since announced they are getting into the game, with clothes that are described as "après sport" or "gym-to-the-office," it's fairly clear that athleisure is becoming bigger than a trend. This has also been evidenced by the number of people who seem to think it appropriate to wear leggings or yoga pants practically anywhere, but I digress. There is clearly an overwhelming desire for leisure and sport clothes that are designed well and stylish, given the amount of interest this month in the introduction of Net-a-Sporter , a new channel from the online retailer Net-a-Porter that is dedicated to "sportswear that is as chic as everything else in your closet." This includes both basic Nike  tanks for $30 and luxury items like a Karl Lagerfeld sweatshirt  for $235, or cashmere and linen track pants from The Elder Statesman  for $600.
Luxury versions of leisure clothes have occupied a niche of fashion for decades (Juicy Couture's velour tracksuits were far ahead of this curve), and, of course, a good deal of these clothes are really no different from the Ts and sweats people have been buying for years, now just with better tailoring and excellent marketing behind them. The taglines and mottos are so adorably inspiring: "Clothing for a comfortably confident life," says Lou & Grey.
But athleisure represents a bigger, and likely permanent, sea change in fashion. It has even started to appear on designer runways, including those famous couture sneakers from Chanel . The reasons are many, but the most obvious cause stems from people who are embracing healthier lifestyles, while also demanding more functionality from their wardrobes. The need for everyday comfort, too, plays a role, especially for anyone trying to work fitness into an already overtaxed schedule. Who wants to haul an extra outfit to work?
It makes sense for designers to be coming up with new solutions for racing from spin class to the boardroom, but before things get out of hand, here's one request: Let's leave leggings at the gym.
For real-time insider insights, make sure to follow Eric Wilson on Twitter (@EricWilsonSays ).
Feeling inspired to actually wear your athleisure gear to the gym? Scroll down to check out some of our must-have products for your next workout.
Source: Getty / Kirstin Sinclair 
For the Runner
Put a spring in your step with these vibrantly colored kicks.
Adidas Running Springblade Drive Sneakers  ($180)
For the Dancer
This three-part footwear system protects bare feet from slipping during yoga, dance class, and more.
Nike Studio Wrap Pack Yoga Training Shoe  ($110)
For the Gym-Straight-to-Work Girl
From a compartment to store sweaty gym clothes, to the chic design, this gym bag takes you from gym to work — and everything in between — in style.
Stella McCartney Big Gym Bag  ($150)
Shop even more must-have products  at InStyle, or check out these other stories:
- What Does Your Denim Say About You? Find Out Now 
- The Best Cover-Up Pairings For Your Body Shape 
- How to Pull Off a Crop Top For Your Shape