NEW YORK • Yoga pants are now reporting for duty in offices in America - in yet another sign of how users are further stretching value from the garment.
But back in 1998, the first pairs of yoga pants Lululemon sold were a simple item for women to wear at the studio.
They were a mix of nylon and Lycra-synthetic elastic fibres that provided the stretch and softness to manage all those sweat-inducing contortions on the mat.
Yoga, first as an exercise and later as a cultural phenomenon, had yet to take hold.
At the turn of the century, the pants filled a niche for enthusiasts looking for a higher-end alternative to plain cotton leggings.
Two decades later, they have conquered the closet, even for people who never visit a yoga studio.
In 2014, teenagers began to prefer leggings over jeans. Then people started wearing athletic clothing (or athleisure, but it is mostly just yoga pants) to run errands.
Now, yoga pants are in the office.
The popularity has led to a flood of competitors, from Old Navy's US$20 (S$27.50) pants to Lucas Hugh's US$230 versions.
Lululemon Athletica, largely credited with bringing stretchy pants to the masses, has poured money into developing new fabrics to fend off rivals that now include the world's biggest athletics companies.
Many of its newer fabrics are branded and geared towards specific uses.
Luxtreme is a moisture-wicking, four-way stretch fabric that is meant to fit like a second skin. Silverescent is sold as "stink-conquering technology".
Leggings from competitors use a similar strategy, promoting the versatile pants through branded fabric combinations.
For Adidas, pants boast fabrics like its sweat-wicking Climalite material or the thermal-regulating Climacool and Climawarm to accommodate training conditions.
Likewise, Nike's Dri-Fit material keeps sweat at bay and trainers dry.
What was once a simple stretchy legging, it seems, has become an engineering marvel.
Not too surprising, though, when you realise that about US$48 billion is being spent on activewear in the United States every year.
Now that it has a spectrum of products, Lululemon has opened two stores for those customers interested in still-experimental items.
One, in downtown Manhattan (the other is in Vancouver), looks more like a fashion boutique than a place to buy gear for the gym or yoga studio.
The biggest businesses now in the athletic wear space have invested heavily in growing their womenswear lines, especially in developing new fabrics and features for the once-simple yoga pant.
In 2014, Nike began working towards a US$7-billion sales target for its women's business, reporting almost US$5 billion in revenue.
A year later, it reported that the global growth for women's business was outpacing that of men.
That same year, Adidas began directing its youth brand, Neo, towards younger women.
The German sports giant even brought on Lululemon's former chief executive Christine Day as a strategic adviser.
Adidas quickly became a formidable threat to Lululemon's dominance.
Early steps turned into exclusive designs for women through the PureBoost X line, leading to an even larger emphasis on active tops and bottoms, using technology called Climachill and Techfit, both focused on women's training.
Last year, women's sales for Adidas grew by 28 per cent, making it one of the company's strongest segments.
Active bottoms and leggings are now a US$1-billion industry, according to NPD Group analyst Marshal Cohen.
These days, there are more than 11,000 kinds of yoga-specific pants available at retailers worldwide, according to data from retail research firm Edited, across both men's and women's apparel.
"Now that this easy-to-fit, easy-to-find, easy-to-wear, easy-to-care-for product has emerged as a fashionable product at the same time, you've got the perfect storm," Mr Cohen said.
"You have to be doing something pretty wrong to not have success in this type of product."