
Kelsea Ballerini sure knows how to whittle her middle! Clad in a yellow and black sequined Nicolas Jebran minidress at the American Music Awards in L.A. on Tuesday, October 9, the nominee showed off her tiny waist and tight core.
Her trainer Erin Oprea tells Us Weekly the “I Hate Love Songs” crooner, 25, pushes herself hard for her abs and fit figure! “All my clients are determined,” she says. “All my clients have big goals because they’re all on stage. They’re all photographed on a red carpet, or with a new single. All of them are superdisciplined.” Ballerini, in particular, knows how to mix business with pleasure. “She is a hard worker but she loves to laugh too. She’s a lot of fun,” notes Oprea. “There’s never a dull moment working out with her.”

The Nashville-based trainer — who also works with Carrie Underwood, Jana Kramer, Maren Morris, Kellie Pickler and Kacey Musgraves — utilizes Tabata (20 seconds of intense exercise of six to eight rounds, followed by 10 seconds of rest, for approximately four minutes) and other high-intensity interval training (HIIT) techniques in her fitness regimens. “One of my favorite exercises that I have all my clients do is this,” Oprea told Us in May of a leg exercise. “Stand on your right leg — all your weight is on that leg. Keep your left toe right next to your heel, it’s just for balance. Go all the way to a squat. So your right leg is parallel to the ground. Standing just halfway, you take it back into a lunge. So you’re never fully standing. You come back in and go into a squat, come up halfway and take it back into a lunge. So it’s two movements without fully standing.”
As for core and ab workouts, she uses a similar technique where one move will roll into the next for an intense burst of activity. One of the go-to moves she uses with Ballerini is alternating crunches on a Bosu Ball. “You sit low on the Bosu Ball, take your left arm and crunch it up to your right leg, which is straight out — and crunch up, then take it down. I describe it as open-close,” explains Oprea. “Keep your other hand on your belly.” The exercise is “fantastic because there is no rest point. Even in the down point, your abs have to stay engaged,” says the pro. With Ballerini, she adds, “We’ll do three to four sets of 15 with one arm, and 15 with the other. Then 20 straight up with both legs on the ground, knees bent and feet flat.”

Another core favorite? The move Oprea orchestrated during the July 3 group workout she did with Ballerini and pals Morris and Carly Pearce. She told Us at the time the friends did “lots and lots of abs,” noting that the waist work included 40 butterfly crunch pulses “followed by elbow planks with hip dips for 30 seconds, then side planks for 30 seconds each.”
Ballerini even counts on the pro’s advice when she’s traveling! As the country star captioned an October 5 Instagram post of her working out, “pre show sweat in this pretty Nevada weather… thanks for kickin’ my rear end all the way from Nashville @erinoprea.” Indeed, the former Marine tells Us she’s always available for her charges. “I do FaceTime a lot with my clients when they’re on the road,” she admits, adding that Ballerini, who also loves to do SoulCycle when she’s in L.A., is no exception.
And the dedication is worth it — for both parties. “I’m proud of all my clients! I’m like a kid in a candy store,” says Oprea. “They send me pictures and they are so happy, and that’s what makes me so happy. When they feel good, that’s my reward.”