Miranda Kerr was nervous about the Victoria's Secret fashion show.

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The 29-year-old model - who has 22-month-old son Flynn with husband Orlando Bloom - has worked for the lingerie firm since 2007 but that doesn't mean she wasn't anxious about appearing in their famous catwalk extravaganza earlier this month.

Explaining her nerves, she said: "You're in underwear in front of millions of people."

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The Australian beauty "amped up" her diet and exercise regime ahead of the show, with "green juice" being a big part of her preparations.

She told People magazine: "I amped up my training. [I've been] doing a lot of Pilates, yoga, boxing and working my core, butt and legs.

"I also drink healthy green juices everyday, and protein shakes."

And despite her nerves and the effort involved, Miranda insists it was all worth it for the spectacular show - which featured performances from Rihanna, Bruno Mars and Justin Bieber - because it is such an exciting occasion.

She said: "I love feeling the music when I come down the runway. The energy is incredible."

The Victoria's Secret catwalk show airs in the US on CBS on December 4.