Katy Perry 'Sore And Exhausted' After 'Part Of Me' Video

'I know how to carry my weight a little bit more,' she says of military training for the just-premiered clip.

One of the many reasons to admire Katy Perry is for how honest she is with her fans in revealing how she struggles with the same mundane annoyances in life that we all do, like watching what we eat and exercising.

During MTV First: Katy Perry" on Tuesday, when Perry premiered her new "Part of Me" video, the pop star revealed that during the holidays, she gives herself a free pass and goes into full-on "Stay Puft Marshmallow mode." So she had some preparation to do before shooting the combat-heavy clip, going on a strict diet and exercise program.

"I got on a meal plan. I'm still on that meal plan, although I cheat a little bit — I have to live!" she admitted. "I got a fantastic person to work me out and get me into really good shape."

Perry said she performed a lot of the stunts in the video, including learning how to flip and carry people.

"On the actual base, I did a lot of things. I flipped girls, I learned how to fireman-carry," she said of the maneuver used to rescue wounded or unconscious victims of fires or other accidents. "I know how to carry my weight a little bit more," she said, before admitting there was one task she wasn't able to master.

"One thing I can't do, and I hope that there are other people out there that feel the same way, is climb a rope," she said. "Oh my gosh, it's so hard to climb rope! It's all about grip and arms. I tried five or six times on set, but I had to cheat that shot. My hands were shaking."

Though the production of "Part of Me" was a lot of hard work — actual blood, sweat and tears — Perry talked at length about how much she learned from the Marines she worked with.

"This music video, as much as I was sore and exhausted, I was so educated on people in the service who I've always respected, but this time the respect goes beyond and above anything I could've imagined," she said. "The stuff that they go through, the loyalties and strengths that they all possess, it seems like they are seriously, not to sound weird, but it's seriously the heart of America."

Stick with MTV News as we roll out more exclusive news from our "MTV First: Katy Perry" interview!