By Aly Semigran
Mar 13, 2015 @ 9:00 am

There's an episode of Girls in the first season in which Lena Dunham’s character Hannah gives up pretty quickly after going for a run with her then-boyfriend Adam. While it was hilarious, that sort of scene may never happen again on the show—because the leading lady is on, as she told David Letterman, "a little bit of a physical fitness kick." Dunham visited The Late Show on Thursday, where she chatted about getting in the best shape of her life thanks to mat work, pilates, and "small movements that look easy, but are torturous."

Dunham, who said she was inspired to get in shape after lagging behind her "exercise fiend" parents, has even been participating in acro yoga. The actress/writer/director, who said that acro yoga "takes a lot of core strength," even shared a picture in which she's in a complicated pose with her instructor. Letterman noted that the star looked better than ever, to which Dunham confirmed, "I feel great."

Watch Lena Dunham chat with David Letterman about her newfound love for working out by clicking on the video above.