10/11/2013 09:26 EDT

Kate Upton Shows Off Her Sports Illustrated Body In Tight Workout Clothes (PHOTO)

So that's how Kate Upton gets her gorgeous body!

Celebrity trainer David Kirsch posted side-by-side Instagram photos on Thursday showing the model flaunt her famous Sports Illustrated figure in sexy exercise clothes.

But the 21-year-old hottie wasn't just doing a gruelling workout session - the "Cat Daddy" sensation was also modelling Heidi Klum's collection of New Balance trainers (that's right, even models design fitness gear these days).

Although the "Project Runway" host wasn't photographed in her own designs, Kate dutifully took over modelling duties, flaunting her toned legs and pert derriere in black lycra pants, a red tank top and a pair of matching sneakers.

Upton looked so smokin' that Klum actually tweeted her approval, saying,

Who would have thought that a little girl from Michigan would have have grown up to be such a stylish superstar?

Kate's hard work at the gym has paid off:

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