The 'Zero Dark Thirty' actress admits she had bad form when sprinting and it wasn't until her 'The Debt' co-star gave her some pointers that she learned how to run like she was in an action movie.
She said: "Sam Worthington, who I acted with in 'The Debt', had to teach me [how to run], because I used to look like such a wimp when I tried. He told me to think of Tom Cruise when he runs in movies - that's what I was aiming for!"
Despite perfecting her running technique, the 36-year-old star has another worry - she swims like an "old lady".
She explained: "I mean, I can swim how an old lady swims, where you stick your head above the water and you just move your arms out like a frog. But not properly."
Jessica also praised another co-star, Brad Pitt, with whom she starred in 'The Tree of Life', for being an inspiration to her career.
She said: "Working with Brad Pitt [was a turning point]. He's too humble to make it obvious that he's giving you advice but I would watch him on the set and follow his example."
The 'Mama' beauty is known for her luscious red hair, but says she "hated" her flame-coloured locks as a child and "just wanted to look like everyone else".
She added: "Even when I first moved to Los Angeles, I don't think anyone knew what to do with me because I wasn't a typical 'babe'. But it's become my defining feature and now I adore it."