When it comes to training for Hollywood blockbusters, nothing is off limits.
Just ask Michael Fassbender who revealed he's been using a bikini body challenge program to get in shape for the latest X-Men film, reports news.com.au.
In an interview on The Project, Fassbender, who plays Magneto in X-Men: Dark Phoenix, explained he didn't do many stunts in the film other than the wire work.
"Although I do have to say, I've been using this app which is an Australian woman … Kayla Itsines," he said.
"It started off as the bikini body app and now it's called the sweat app," he said, turning to co-star James McAvoy.
However, news.com.au can confirm the Sweat app is not in any way affiliated with the Bikini Body Challenge.
The 42-year-old, who stars in the film alongside Jessica Chastain and Sophie Turner, added although he wasn't too sure how many men used the app, he would love to see more blokes download it.
"I do and I'm saying other men should too!" he said.
Itsines, who recently gave birth to her first child Arna Leia Pearce, is the founder of the Bikini Body Guide and co-founded the Sweat app with her fiance Tobi Pearce.
While there's nothing saying men can't be part of the "Kayla Army", their target is mainly woman, particularly those aged between 20 and 35 years of age.
In 2014, the Adelaide-based couple created the 12-week Bikini Body Guide fitness program. Itsines, also a personal trainer, published before and after photos of her clients on her Instagram profile, which ended up gathering a huge fanbase that dubbed itself "Kayla's Army" and was a phenomenal success for the couple.
Pearce helped create the company 'Sweat', publishing e-books and an app under the same name on which fitness trainers (including Itsines) host various fitness programs.
Both Kayla and Tobi have a combined wealth of $486 million.
Last year Kayla came fifth in the Financial Review's Young Rich List.