Hilary Duff HDUFFMARKET030108_10.jpg

While Joel's current seems to be shedding baby weight at a rapid pace, his ex is bulking up!

With muscles, people, just look at those arms!

After an afternoon at the gym, Hilary stopped by Whole Foods where she displayed her starlet super-strength by carrying all the grocery bags with just one arm.

I definitely wouldn't want to challenge her to an arm wrestling competition!