A sturdy support system with sensible coverage is the new lace.

Today’s boudoirs are increasingly filled not with barely-there bralettes and sexy negligees, but tried-and-true sports bras. More than any other intimate apparel, sports bras and shapewear have seen the biggest sales growth in the last three years, according to the NPD Group’s Consumer Tracking Service.

In the last year alone, sports bra sales have increased by six percent, in part thanks to millennials, who spent a third of their bra budgets on those of the athletic variety.

The reason for this sales growth will shock absolutely no women.

“Women of all ages are finding sports bras more comfortable,” NPD Group chief analyst Marshal Cohen tells WWD.

Now, lingerie startups are increasingly pivoting to sports bras, and celebrities are turning the style into red-carpet moments. Supermodel Emily Ratajkowski recently wore only a “cozy as well” sports bra coupled with an open blazer and leggings to a breakfast event. In June, Kim Kardashian launched her Kimono shapewear line –– which she is renaming after much backlash.

Apparently, even young women have had it when it comes to putting on a show: “Age doesn’t matter much anymore when it comes to comfort,” Cohen says.

Adding to that, there’s a decreasing stigma against athletic wear, given that offices now have less strict corporate dress codes, and more people work from home. Plus, women participate in a bigger variety of activities throughout the day, the analysts say.

It also helps that it’s now totally acceptable to wear underwear as outerwear, or just underwear alone –– á la the Kardashians’ recent family portrait-slash-advertisement for Calvin Klein, in which the whole squad was decked in the brand’s underwear sets.

“You can have different style bras, but at the core of [the] sports bra, it’s about [the desire for] comfort,” president of an intimates group Mary van Praag tells WWD.

Victoria’s Secret has notably not gotten behind the trend, although that’s no surprise coming from the intimates giant, lingerie startup COO Romain Liot tells WWD.

“They are in the business to sell bras to please the eyes of men,” Liot says.