We took to the streets of New York City to capture the trend that's killing the traditional fashion market

Outfit choice: Gap clothes and Ryka sneakers.

Reason: "I call them glorified pajamas," she said. Aditi likes the fact that she can teach easily in these clothes, but also be dressed-up enough to meet with clients after. "I try to find clothes that are comfortable but look good," she said.

Is this a one-off? This lady spends a whole week in these clothes because of her work.

Outfit choice: Head-to-toe in Gap Fit, plus New Balance sneakers.

Reason: Olga is on her feet all day, so these clothes are a practical choice. "I change on the weekend," she said. "But I can go to a restaurant like this. I don't care."

Is this a one-off? No.

Outfit choice: Alo, Lululemon, Gap, North Face, and Asics.

Reason: Jen had the day off when we met her, and she was on her way to an exercise class. She'll spend the rest of the day in these clothes, she said. "I don't have to think about putting an outfit on," she said.

Is this a one-off? She can't work in these clothes, so it's weekend-only wear.

Outfit choice: New Balance, Lululemon yoga pants, and a Reebok sweatshirt.

Reason: "Fitness is my life," said Randy, who works out or runs every morning. "I think it's stylish nowadays – I can wear it for work or working out, and it's good in both places."

Is this a one-off? No, Randy wears athletic clothing six days a week.

Outfit choice: Nike Zonal Strength pants, Nike jacket, and a SoulCycle tank top.

Reason: "It's casual and trendy right now," Sam said. "[It] is fashionable so you don't feel like you are underdressed."

Is this a one-off? No. Jen works out four times a day, six days a week, so athletic wear is her go-to choice.

Outfit choice: LeBron James sneakers, Adidas track pants, and an H&M shirt.

Reason: Comfort. "If I am not comfortable then I am going to feel uncomfortable and think everyone is looking at my outfit like it's not something to wear," he said.

Is this a one-off? No. This is his everyday wear.

Sam wears lime green and burgundy LeBron James sneakers.

Outfit choice: Reebok leggings and Nike sneakers.

Reason: Maria was on her way to a CrossFit session when we met her.

Is this a one-off? No. This is everyday wear for Maria.

Outfit choice: Anthropology leggings, Athleta top and Converse sneakers.

Reason: Alexandra was on her way to a yoga class when we met her, but she says she finds the clothes comfortable and cute.

Is this a one-off? No! "I'm either in scrubs or athleisure. I forget how to dress," she said.

Outfit choice: Nike.

Reason: "Athleisure is convenient. It's uncomfortable to be in nice shoes for the entire day," said Sanjana. "It's comfort over everything in New York, but I try to dress it up a bit so it's not frumpy."

Is this a one-off? Sanjana spends four days a week in her athleisure.

Outfit choice: "Athleta, Asics, Gap, Zara, and Burberry; a bit of everything," said Kirsti.

Reason: "I can wear whatever I want for my work," she said. "I live in my activewear, I'm a mom, so I'm busy and bouncing around."

Is this a one-off? No. "You will find me in my athletic wear every day," she said.