For up-and-coming high-end fitness brands, Equinox members make ideal customers.

“When we were planning our first product line, our designer sat down at different Equinox juice bar locations and just people-watched,” said Aaron Luo, CEO of Caraa, a two-year-old brand that specializes in luxury performance accessories. “She interviewed members in order to understand their pain points, and we started designing from there.”

Once Caraa launched its first collection — a line of bags designed to go from the office to the gym — Luo scheduled a meeting with Equinox’s head of retail. Luo wanted the line, inspired by Equinox members bogged down by what he calls the “too many bags syndrome,” to be sold in the gym’s retail shops. Since that initial conversation, Caraa, a primarily direct-to-consumer brand, has expanded its Equinox partnership from five shops to 45. At the end of April, the brand released a limited-edition tote exclusively for Equinox.

Equinox, which has opened 90 luxury gyms globally since 2015, is building out its retail presence in order to keep pace with the steady demand for athletic wear. According to Morgan Stanley, the athleisure trend is propelling the market to reach $83 billion by 2020, and while some brands have fallen prey to the saturated industry — like Kit & Ace, which just closed all but nine of its 61 stores — opportunity is ripe for Equinox to flex its lifestyle muscles. Other boutique fitness companies, like SoulCycle, Barry’s Bootcamp and Peloton, a spin studio and bike retailer, have also built out shops in order to capitalize on their cult-like followings. (SoulCycle is owned by Equinox.)

Equinox, a privately held company, is hoping to become more of a shopping destination for its members through a variety of brand partnerships. Its draw: frequent foot traffic: Its members visit an average of four times per week, according to a 2016 statement from former CEO Harvey Spevak. Equinox’s membership rates are also prohibitively expensive — averaging $200 per month in New York City — meaning those frequenting its fitness machines wouldn’t bat an eye at a $225 gym bag, which is what Caraa’s exclusive bag retails for.

Through partnerships with Equinox, brands are taking advantage of that concentrated, high-spending clientele and their regular visits, as more traditional wholesale partners, like department stores, are struggling to draw the same volume of customers. Equinox stocks a rotating supply of brands in its shops, including Nike, Lululemon, Spiritual Gangster, Alice + Olivia, Joie and La Made.

“It’s an interesting and challenging time for retail, and brands are thinking more creatively and outside the box. This climate is actually forcing people to do so,” said Cassandra Campa, senior buyer at Equinox. “It’s been on our mind for years: How do we make our experience different? Today, we have more vendors coming to us and presenting more ideas for how to build a partnership beyond a buy.”

One such partnership is an in-gym pop-up series that launched in 11 Equinox locations on Monday. The first brand to pilot the series is menswear performance brand Rhone, which has sold through Equinox for three years. The collaboration will reserve branded shop-within-shops at the participating Equinox locations, and will sell the full collection of Rhone menswear. Typically, Equinox tailors its buys from vendors to only a few items per brand.

“We saw menswear growing, and Rhone was at the center of that,” said Campa. “For brands as well as our business, partnerships have become especially important in this retail climate. This was the natural next step in order to offer something new to members.”

According to Rhone’s svp of sales, Cortney Ansel, items on sale at Equinox see a 70 percent sell-through rate. While the brand also sells through wholesale partners like REI, Bloomingdale’s and menswear boutiques, Ansel said Equinox members, in the fitness mindset, are more inclined to make a purchase.

“With the changing retail landscape, a pop-up concept allows us an opportunity to know our customers better by location. We can use it to figure out where a standalone store might make sense,” said Ansel, who added that about half of Rhone’s business is done through its e-commerce store. “One of the things we have noticed is when a guy is in that health and wellness state of mind, he is ready to buy activewear. He’s ready to spend $70 on our shorts, and so that’s where we want to be.”

Caraa’s Luo shared a similar thought process when weighing options for wholesale partnerships.

“When we start thinking about doing wholesale, we don’t have Barneys aspirations. If we get into the department store space, that’s great, but we’re focusing on what we know about our customer,” said Luo. “There’s a lot to be said for our bags sitting exactly where she works out. We want to be where the customer is, and the customer is at Equinox.”

The initial run of the Rhone shop-within-shop pop-ups will last through August, and Campa said the company plans to test more of the same model. Equinox doesn’t sell e-commerce through its online site, but brand partnerships are fleshed out through Equinox’s marketing and social media channels to bring new retail activations to members’ attention.

“There’s a lot of noise out there, so we want to connect with our brands in a meaningful way that’s right for our members,” said Campos. “Pop-ups and exclusives will become an important part of our strategy, as will exploring e-commerce. For now, we’re really lucky to have these physical locations that can serve as a platform for new brands.”