When you think about all the films she's been in over the past couple of decades, it still comes as a huge surprise to me that Scarlett Johansson is still only 34 years old.

Most people will recognise her as Black Widow in the Marvel Cinematic Universe or the film adaptation of Ghost in the Shell, but she's acting since she was 10 years old, and earned accolades for the 2003 movie Lost In Translation at the tender age of 19.

As an actress at the highest level for so long, ScarJo's got her work cut out in order to stay in tip-top form, and unsurprisingly she's got a personal trainer to help her through the tough stuff of keeping her famous figure as good as it can be. What's slightly more surprising, though, is that Scarlett Johansson has a secret trick to help keep her in shape. Well, that's according to her personal trainers.

Scarlett Johansson [[imagecaption|| Credit: Getty]]

Although you wouldn't readily associate chocolate with a good, clean workout without slipping the word "sabotage" in there somewhere, brothers Ryan and Eric Johnson say that a good bit of dark chocolate can go a long way toward enhancing your fitness routine.

Despite being primarily known as strength and conditioning coaches, the Johnson brothers know a thing or two about nutrition, and over their work with Johansson on Captain America: Winter Soldier or Ghost in the Shell, they've encouraged ScarJo - as well as their other clients - to indulge in a little bit of dark chocolate.

"We're always searching for a good pre-workout supplement but most of the things you can buy in stores are full of sugar and caffeine," explained Eric, and with plenty of health benefits to dark chocolate, they wanted to impart that knowledge to Scarlett Johansson.

Scarlett Johansson [[imagecaption|| Credit: Getty]]

"We already drink way too much coffee and most of our clients do too, so we wanted to find something which was more naturally organic and that would give you the same benefits," continued Eric.

"Dark chocolate releases dopamine and has a lot of benefits such as vasodilation which is basically that pump that people are after when they're trying to build muscle. It also benefits your brain function because it stimulates your brain cells to release that dopamine. And it also releases serotonin which is going to calm the nervous system down."

Dark Chocolate [[imagecaption|| Credit: Getty]]

But apart from all those physical and nutritional benefits, getting in a piece of dark chocolate before hitting the gym can also have a psychological effect, Eric explained.

"It creates this positive feedback loop with your brain — now that you're getting this piece of chocolate before your workout you're creating a positive association with your training session and you're getting more excited to get to the gym... you have something to look forward to."

Dark Chocolate [[imagecaption|| Credit: Getty]]

But ladies and gentlemen, this doesn't mean you can gorge on a Mars Bar before a gym session, mumbling "ScarJo does it" through bites of chewy nougat. Instead, Eric suggests you should have two to three pieces, which is roughly a third of a bar. Don't overdo it, and maybe - just maybe - you'll be in the next Avengers film.

I mean, probably not.

Scarlett Johansson's personal trainers reveal why she always has dark chocolate before a workout