Incorporate this move into your daily workout routine to flatten your belly and strengthen your core.

By Nicole Love
October 16, 2015

The key to a strong core isn't just constant crunches. To really flatten your belly, you've got to continue to challenge those mid-section muscles with new exercises. Here's a move you can incorporate into your routine to surprise your core: the double-leg stretch.

Health's contributing fitness editor, Kristin McGee, demonstrates below.

Here’s how to do it: Start out by lying on your back. Pull your knees to your chest and lift your head and neck off of the floor, extend your arms overhead and your legs out, then circle your arms around and pull your knees back in. Repeat 8 times.

Trainer tip: Remember to engage your abs for the best results.