Margot Robbie's insane workout schedule for Suicide Squad

Will Smith and Margot Robbie, star in the movie Suicide Squad.

If you think Margot Robbie looks great in her hotpants as Harley Quinn in Suicide Squad, be warned: it was the product of a whole lot of hard work.

In order to shape up to portray the comic book antihero, the Aussie-born Hollywood star worked out with trainer Andie Hecker for three hours a day, most days of the week, for three weeks - all while shooting the movie at the same time.

"She was a total trooper," Hecker tells People Magazine. "It was very satisfying to see her body change into exactly what she wanted it to look like in such a short time."

Actress Margot Robbie. Photo / AP

So what exactly was the 26-year-old former Neighbours actor subjected to during this gruelling three-week boot camp? Hecker says she sculpted and toned her body with a mix of pilates, ballet and more.

"We also mix in non-bulking cardio such as jump rope, rebounder and ballet jumps - which are surprisingly the most challenging form of cardio I've ever come across," she says.

Hecker focused her exercises on Robbie's abs and butt, given that those were constantly on show in the actor's skimpy costume in the film.

"We did a lot of heavy-weighted, low reps of arabesque pulls hooked up to resistance pulleys, as well as arabesque lifts with heavy ankle weights in order to build and lift the butt," she says. "We also did a ton of side series outer thigh work, targeting outer glutes with high reps and low weights, to pull those muscles in and create a beautiful line from the waist to the upper thigh."

Margot Robbie stars as Harley Quinn in the movie, Suicide Squad.

Sounds ... hard. Excuse us while we continue to schlep to the gym twice a month and wonder why we don't see results.