A torn hamstring, stomach strain and a pulled calf muscle were just some of the injures sustained by Phoebe Thomas as she prepared to play Hetty Feather.
The ex-Holby City star appears as the much-loved character, created by children's author Jacqueline Wilson, in a theatrical adaptation about to hit the West End.
Despite being a self-confessed fitness fanatic, who works as a personal trainer to the stars when not treading the boards, she admits the circus skills featured in the show pushed her to the limit.
"We did a week of really intense training in circus skills, which involved conditioning work so we could get as strong as the aerial experts," she said.
"During that time I tore my hamstring, strained a stomach muscle and pulled a calf muscle. It's very different from running in a straight line and uses so many muscles but I love doing it and definitely want to keep it up."
Hetty Feather tells the tale of a girl who is left at a Victorian Foundling Hospital as a baby, and her efforts to track down her mother, which lead her to the circus.
Jacqueline Wilson, who is most famous for her Tracy Beaker books, has personally praised Thomas for capturing the indomitable spirit of one of the author's favourite creations.
But readers of any age often have very set ideas about how their most-loved characters should look and act, and children can be particularly unforgiving. So was Thomas nervous about taking on the role of Hetty?
"When I auditioned I hadn't realised how Hetty was right up there with Tracy when it comes to children's affections but once I read the books it was easy to see why," she said.
"When I went to lunch with Jacqueline it dawned on me that I wasn't just bringing to life one of her favourite characters but someone who's adored by so many thousands of children across the world.
"Hetty's independence and fierce sense of self-worth make her a role model for many young people and it was a daunting role to take on but I've had some wonderful feedback."
This adaption of Hetty Feather, which earned rave reviews at Kingston's Rose Theatre and in the ensuing world tour, only takes us up to the end of the first book in the series.
But Thomas said the response had been so fantastic she would love to reprise the role, adding 'watch this space'.
As a 31-year-old playing a young girl, she said she relied on her 'playful spirit' to help channel Hetty's youthful exuberance, as well as studying her nephew and children's friends.
"I rarely think of myself as the age I really am but I had to home in on that openness and lack of preconceptions children have," she added.
"When you're playing someone of that age you need to be able to switch from being incredibly quiet and focused one moment to throwing yourself around the room the next."
Thomas played the gossipy nurse Maria Kendall on BBC medical drama Holby City from 2006 to 2010, but said she felt she had to leave to avoid becoming 'complacent'.
She still works as a personal trainer to some of her old Holby colleagues, including Jaye Jacobs and Hari Dhillon.
She loves to run, she says, because it allows her to clear her mind and enjoy being alone, providing a 'lovely contrast' to her acting career.
Despite the demanding workout required for her latest role, she says it was nothing compared to her toughest assignment - playing the title role in a film about Lady Godiva, who famously rode naked through the streets of Coventry in protest at taxes.
"They hadn't actually got permission to shoot on the streets so it was a case of getting up at 4am and doing it before the streets were really busy," she said.
"I was using my hair in a very clever way to preserve my modesty but I got some funny looks from the bus drivers who went past."
* Hetty Feather is at the Vaudeville Theatre, in the Strand, London, from August 5 to September 6. For tickets, priced £15 to £39.50, visit www.hettyfeatherlive.com or call the box office on 0844 412 4663.
