We don’t like to play favorites, but…for planks, we’ll make an exception. “They are, without a doubt, the best core exercise there is,” says trainer David Kirsch, who works with Kate Upton and Liv Tyler. The harder-than-they-look poses in this workout take it up another notch. Adding movement—like, say, raising an arm off the ground—while holding a plank position increases the challenge to your abs. It also recruits your legs, glutes, back, shoulders, and arms to get in on the action—meaning it can firm you up all over.
Try this routine, created by Kirsch, two or three days a week. Perform 10 to 15 reps of each exercise, moving from one to the next without resting. (If your form starts to slip, raise your hips to give your core a break, or place one knee on the floor for a few seconds. And remember that proper plank form means hands on the floor directly under your shoulders, with your body forming a straight line from head to heels.) Rest for one minute, then repeat the circuit up to four times total.
Plank Row and Kickback
Start in a plank position with your right hand resting on a dumbbell (A). Row the weight to your chest (B); pause, then straighten your elbow until your forearm is parallel to the floor (C). Pause, then reverse the movement to return to start. That’s one rep. Complete all reps, then switch sides and repeat.
Plank with Front Raise
Start in a plank position with your right hand on a dumbbell (A). Extend your right arm straight out in front to shoulder height, keeping your hips parallel to the floor (B). Lower slowly back to start. That’s one rep. Do all reps, then switch sides and repeat.
Rotating T Extension
Start in a plank position (A). Rotate your torso to the right, raising your right arm toward the ceiling as you roll onto the outside of your left foot (B). Pause, then reverse the movement to return to start. Repeat on the other side. That’s one rep.
Start in a plank position. Bend your right knee toward your left elbow (A). Pause, then return to plank, keeping your right foot raised a few inches off the floor. Then angle your right leg out to the side while keeping it extended (B). Pause, then reverse the movement to return to start. Repeat on the other side. That’s one rep.