Halle Berry. Picture: Instagram

Halle Berry's personal trainer has revealed the star's fitness secrets, including her focus on martial arts to keep in the best shape possible.

The 51-year-old star has kept her fans up to date with her fitness regime as she works on her enviable figure, and her personal trainer has revealed the "bulletproof battle plan" they work on together.

Speaking to E! News, Peter Lee Thomas said: "She pretty much had a checklist of things she wanted as far as her physique is concerned and we had a bulletproof battle plan...

"You better believing we are doing some boxing, some kick boxing, some Muay Thai... I'm definitely working on those skill sets with her and she's also doing strength and conditioning.

"She's using kettle bells, bar bells, dumbbells, working on the pull up bar, doing dips, sprinting pushing heavy things, pulling stuff. It's just a really dynamic way to jumpstart anyone's metabolism."

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The pair work together five days a week, and Halle's trainer has praised her dedication and resilience when it comes to her work ethic.

He added: "I have never met anybody that works harder and trains harder and is just so resilient. She is getting faster, stronger and becoming more athletic. I've never met another person who can do it like her."

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The 'Monster's Ball' actress - who has 10-year-old daughter Nahla with her ex-boyfriend Gabriel Aubry and son Maceo, four, with her former spouse Olivier Martinez - recently spoke about her first job, revealing she got fired as a bartender for making drinks too strong.

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She said: "I wasn't even old enough to be a bartender. I was in a big city, and I was 19 years old.

"I wasn't very good, but I ended up being good because I would say, 'OK, so what do you want?' And they would say, 'Sex on the beach,' and I would say, 'Interesting, what is in a Sex on the Beach?' And they would tell me, and I would just start pouring.

"I put way too much alcohol in everything, so imagine the tips I got, but I lost my job in about three months.

"They were going through liquor like you would not believe."