Los Angeles - Caitlyn Jenner has discovered "why girls need a sports bra".
The 65-year-old star is seen playing tennis in a new clip from I Am Cait, the documentary following her new life since she transitioned to a woman, and the footage shows her joking about understanding the importance of wearing supportive underwear.
In the clip, she said: "Now I know why girls need a sports bra!"
The new teaser also shows Caitlyn - who was previously known as - meeting with school teachers as part of her efforts to help educate about the transgender community, as well as sharing a touching conversation with her 89-year-old mother, Esther Jenner.
Elsewhere, the clip sees Caitlyn's stepdaughter Kim Kardashian West going through her wardrobe and breaking some awkward news to her stepparent - who separated from Kim's mother Kris Jenner last year after 23 years together.
As Caitlyn shows Kim a black and gold dress in her walk-in closet, the 34-year-old reality TV star said: "Mom has that".