ThirdLove is aiming to become a lifestyle brand. Its CEO reveals how its activewear line can compete against Lululemon and Outdoor voices in the $172 billion market.

• ThirdLove is expanding into activewear in an effort to become a full-fledged lifestyle brand.
• The collection comes after releasing lounge and sleepwear lines earlier this year.
• The effort positions the company to vie for a piece of a $172 billion market.

First ThirdLove came for Victoria's Secret. Now, it's got its eyes on Outdoor Voices and Lululemon.

ThirdLove - a direct-to-consumer company best known for its bras and lingerie - expanded into activewear last week with a line of leggings, sports bras, and tops. The collection comes on the heels of the brand's initial foray into apparel with the debut of loungewear and sleepwear earlier this year. These releases are part of a larger effort to establish ThirdLove as a full-fledged lifestyle brand, according to co-founder and CEO Heidi Zak.

"This is another big step for us as a brand, to go into a different category," Zak told Insider, adding that the collection is also the first to feature the company's branding overhaul, which includes a brighter visual palette.

The effort also allows ThirdLove to vie for a piece of the activewear market, a category that has grown significantly over the past two years, thanks in large part to the pandemic. In 2020, athletic apparel was estimated to be valued at $172 billion and is on pace to hit more than $221 billion by 2026, according to data from Global Industry Analysts.

According to Zak, an activewear collection had been in development at the company for the past two years and was inspired directly by consumer demand. Even before the brand had started selling apparel, the website's top search terms included "activewear" and "sports bras," she said.

"When we think about product lines and sizes, we're using qualitative and quantitative data to inform where we're going next, where there's a good opportunity, and where our customers want to see us," Zak said. "Listening to them is definitely really important in terms of when we think about entering new categories. "

Leveraging customer feedback and data has been a significant focus for ThirdLove. Earlier this year, the company launched its virtual fitting room, a feature that uses data from more than 17 million women to help inform purchasing decisions and allow shoppers to identify the best fits and styles for their body types.

The ThirdLove activewear line also used customer feedback when designing its products, settling on three different levels of physical activity: Kinetic, its high-impact collection for sweaty workouts; Flex, medium-impact apparel for less intensive workouts and running errands; and Muse, the low-impact athleisure line.

The sports bras, in particular, have a nuanced focus on fit. The line comes in cup sizes B to G, and its Kinetic collection includes back closures to "so you don't have to yank it over your head," Zak said.

According to Zak, the Kinetic collection involved the "heaviest investment in R&D," including extensive fit testing across body types and activity levels and beta trials with the brand's most top customers.

It's this focus on fit that Zak believes sets ThirdLove apart from competitors like Outdoor Voices and Girlfriend Collective, brands she said are a bit more focused on "style and fashion versus really saying how do we make a sports bra that is really going to support your breasts while you're doing certain movements."

In just a week since launch, Zak said sales are exceeding expectations, with particular interest in the high and medium-impact products. "It's really furthering our expansion as a lifestyle brand," she told Insider.