Nothing can stop Maren Morris from fitting in a workout even in her third trimester. “She is amazing. She looks stunning, but she has worked her butt off for it. I am really proud of her,” her trainer, Erin Oprea, told Life & Style exclusively while partnering with Dymatize, the world’s most trusted athletic nutrition brand, to launch Resolve to Inspire’s $25,000 Gym Contest.

The 4 x 4 Diet author, 41, has the country star, 29, modify some moves, but overall, they’ve “kept up with most of the same stuff” during their sweat sessions. “We still do all of the lunges and squats,” she explained. “We’re not doing abs. We still do core, so you can still do bird dogs, side planks, things like that as long as you know how to engage your core. We have been able to continue doing lots of fun stuff.”

Even though Erin can’t be with the “My Church” crooner all the time, Maren makes sure to squeeze in some time to move her body at home or on the road. “She loves Tabata,” the personal trainer revealed. “She does a lot when I am not with her, too, so that’s really fun. She actually had posted one where she did it on her own without me, and I was like, ‘Yes!’ It’s like a proud mom moment.”

Maren Morris With Erin Oprea and Ryan Hurd
Courtesy of Erin Oprea/Instagram

For those wondering what exactly Tabata is, we’ve got you covered! “It’s like a four-minute workout,” Erin explained. “It’s 20-second bursts of exercise followed by 10 seconds of rest for 8 rounds. You can do eight rounds of squat jumps, you can do shoulder presses for one round, the next round could be squats. There are ways to change it up to get every level to do it.”

Interestingly enough, Erin’s clients might be in the country world, but they actually listen to “the most random” music while training. “I feel like music is such a personal thing and what motivates one person is totally different than the other and what motivates you one day might be different the next day, so everyone kind of plays a playlist they are in the mood for that day,” she shared. “A lot of times, we work out with Maren and [her husband], Ryan Hurd, together. So, it depends on who is picking the music for the day. Music is not always on, sometimes we are watching TV shows.”

As for what the brunette beauty eats, Erin suggests all her clients “just eat clean” and try to eat starches in the morning, so you can burn them off later in the day. “I love oatmeal, I love eggs, I love salmon, I love chicken,” she said. “My meal plan on my app, Pretty Muscles, is all based off my book — it’s all about learning to live a clean, healthy balanced lifestyle.”

At the moment, the Texas native hasn’t expressed whether or not she wants to work out with her child, but Erin imagines she will. “Everybody does,” she said. “All my clients — the babies are climbing on them; the kids are climbing on them.”

Maren Morris and Kelsea Ballerini With Erin Oprea
Courtesy of Erin Oprea/Instagram

At the end of the day, Erin wants everyone to feel good about themselves and feel confident. “My proudest moment with my clients, in general, is when they get dressed for the red carpet, and they send me a picture, and they say, ‘I feel so good today.’ That is like the biggest trainer victory you could have.”

Meanwhile, if you’re trying to up your fitness game and get legs like Carrie Underwood or Kelsea Ballerini — after all, Erin was the brains behind their sexy physiques — her new app is available for everyone to use. “Not only do I have awesome workout apps, workouts that everybody can do, but I also have a full meal plan in there. It’s kind of got everything in one,” she said.

BRB, we’ll be at the gym if you need us!