Watched part of it. When Jenner is seen stretching, I was surprised to see him, while standing, raise first one knee and then the other knee to the height of his chin - wouldn’t think the average runner couldn’t do that and this ability would be limited to gymnasts.
He is a former Olympian and present Kardashian, hence, has easy access to the best gyms and trainers in Hollywood.
Very useful pasttime, being a gymrat, especially when everybody in the family but you was getting tons of attention.