Los Angeles: Actress Ruby Rose has admitted she keeps her abs defined by doing 300 sit-ups a day. The "Orange is the New Black" star keeps her washboard abs intact by following the gruelling regime every evening, reports femalefirst.co.uk. Taking to her Instagram account on Thursday night, the 30-year-old actress uploaded a photograph showing off her abs while wearing a skimpy crop-top. "Life is better after 300 sit-ups," she captioned the image. Rose recently shared she wishes she had a perky backside. She was bombarded with messages from fans claiming she had "no a**" after she uploaded a photograph of herself in a pair of shorts earlier this year. But rather than taking the insults to heart, Rose hit back at the haters by mocking herself and agreeing with them.