ThirdLove is launching its own line of workout clothing including a range of sports bras that the lingerie startup has been working on for two years. The consumer-direct brand’s CEO and co-founder, Heidi Zak, sees an opportunity for growth. “It’s a competitive market for sure, but there’s no company that’s saying sports bra for women, first. When you say Lululemon, I think leggings. When you say Nike, I don’t think sports bra,” said Ms. Zak.