It’s no secret that Kendall Jenner has a banging body, but how exactly did the model get in shape for the Victoria’s Secret fashion show back in the day? Autumn Calabrese — Kendall’s former trainer — is spilling all the details!

“She was 17, so she had about six months until she could legally sign the Victoria’s Secret contract, and she is very naturally lean, she is very tall, obviously beautiful,” the 38-year-old fitness guru told Life & Style exclusively. “So, for her, it was more about just staying lean and toned. We focused on a lot of toning exercises for her legs, for her hips, for her abdominals, we did everything. We weight trained, but we didn’t go super heavy on the weights — we kept it in higher reps, so it was a little bit lighter weights going for that definition even though girls can’t really bulk up.”

Autumn continued to explain what kind of moves she did with the 23-year-old at the time. “We did bodyweight exercises a lot,” she said. “Things like squatting, lunging, glute bridges, so everything is toned and tight — that was the biggest concern. Keeping everything toned and tight, so when she went in for her fitting and she went in for whatever meetings, she would feel like the best version of herself stepping there, coming in that young.”

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peaches and the mangos

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Autumn recalled that the KUWTK starlet was so motivated during that time period. “She definitely still had a really busy schedule even then,” Autumn revealed. “They were still filming the show, she was still traveling, she was still modeling. So, she would be in [the gym] as many days we could. Sometimes it was two days, sometimes it was three days, sometimes a week. When she was in there, she was in there to work. It was like she came in, she knew what she wanted, and she was giving it her all in those sessions, which I absolutely love about her. She was the sweetest girl, and she just has a really great work ethic.”

Autumn was recently featured in an episode of Revenge Body where she trained a girl named Terra. Terra followed Autumn’s “80 Day Obsession” program — which is available on the Beach Body on Demand app — and ended up losing 30 pounds in 12 weeks. So, will the mom of one return to reality TV again? “It would all depend on my schedule,” she said. “If it fits into my schedule, absolutely.”

Autumn explained that she met with Khloé Kardashian — who also hosts the show — while they filmed. “Her and I had a meeting about where we were midway through Terra’s training. Some concerns were there and how we wanted to approach those concerns. So, she came to my house, we had a meeting. That was great.”

Autumn and Khloe Kardashian Wearing an Orange Sweater on Revenge Body

Additionally, Khloé, 35, takes her job with the E! series very seriously. “She is very involved,” Autumn explained. “There is a lot — there are obviously several episodes throughout the season, so she has multiple trainers that she has to meet with, clients she has to keep track of, not to mention her other business adventures.”

BRB, going to the gym ASAP.