For celebrity trainer Kristin McGee—who has toned star clients including Emilia Clarke and Tiny Fey—there's more to enviable abs than what you see in the mirror (or photos). That's why her favorite core moves also help you fend off back pain and let you perform everyday activities without breaking a sweat.

"This bodyweight move targets your rectus abdominis—aka your six-pack muscle—while also strengthening your deep-lying transverse abdominis, which acts like a girdle to pull in and stabilize your entire torso," McGee says. It's basically a crunch and plank in one—only better.

How to do it: Lie down with your back flat on the floor, arms overhead and legs extended straight out, so that your body forms one line from hands to feet. Squeeze your abs to lift both your torso and legs off of the floor and reach your hands toward your toes, keeping your legs as straight as possible and not letting your shoulders hunch forward. Pause for one second, then slowly reverse the movement to return to the starting position. Perform two to three sets of 10 reps.