Pregnant Pippa Middleton: I'm determined not to break into a penguin waddle'

Pippa Middleton has revealed details of her favourite pregnancy exercise routines.

Focusing on her posture, the 35-year-old spoke of her love for ballet-inspired barre workouts and going swimming, in favour of running. 

"I feel far from a ballerina, but I'm equally determined not to break into a penguin-style waddle and plod around with bad posture," Pippa wrote in her her latest column for UK supermarket publication, Waitrose Weekend.

"So with this in mind, I've continued to embrace barre-inspired workouts throughout pregnancy — a form of exercise taken from ballet which involves the small, isolated movements that develop flattering muscle tone or so I hope."

No doubt, Pippa's sister and mother-of-three, The Duchess of Cambridge, has offered her advice on the best pregnancy exercises.

RELATED: Pippa Middleton imitates Kate and Will’s pregnancy tradition

And while it's not known if Kate's suggested it, the mum-to-be seems to have a favourite.

"Swimming throughout pregnancy offers a wonderful feeling of weightlessness.

"From personal experience, I’d confidently say I find it has been the most enjoyable and rewarding form of exercise since I found out I was expecting.

"It’s comforting to know that it’s safe throughout pregnancy and you don’t need to adapt and change too much (unlike most other sports)."

Pippa married James Matthews in May last year and confirmed her pregnancy news in the supermarket publication in April this year.

Kate Middleton's sister is due in October and it's been speculated that the Duchess of Cambridge may skip Princess Eugenie's wedding to be with her sister.