15-Minute Workout: Fresh Flat Belly Moves

Chances are, you've already elevated your ab work onto a stability ball. Smart move: Research shows that crunches atop a ball are approximately twice as effective as those done on the floor. But stop there and you're selling this multitasking tool short. "Most people think a stability ball is just for strengthening their core, but training with a ball can tone muscles throughout the entire body," says personal trainer and fitness author Larysa DiDio. "It also improves flexibility, balance, posture, and coordination." Plus, by swapping your old go-to moves for the following innovative workout, you'll wake up your body and shock it into burning more calories. You'll also increase cardio and muscular endurance (how long your heart and muscles can push before calling it quits).
Three times a week, complete this workout, created by DiDio, as a fast-paced circuit, moving from one move to the next with little or no rest in between. Catch your breath for two minutes, then repeat once or twice more.

Exercise 1 Stability Ball Roll-Out

Kneel in front of a stability ball with your knees hip-width apart, then place your forearms on the ball, hands in loose fists (a). Keeping your back flat, brace your core and slowly roll the ball away from you by straightening your arms; extend as far as you can without allowing your hips to drop (b). Pause, then bend your elbows to roll the ball back to start. Repeat eight to 10 times.

Exercise 2 Stability Ball V-Pass

Lie faceup on the floor, holding a stability ball overhead with both hands, your legs together and extended straight on the floor (a). In one motion, brace your core and lift your arms and legs off the ground, placing the ball between your feet (b). Squeeze the ball with your legs and lower your arms and legs back to the floor (c). Repeat, passing the ball back to your hands. That's one rep. Do eight to 10.

Exercise 3 Stability Ball Single-Leg Press

Rest your upper back on a stability ball and cross your left leg over your right knee (a). Lower your hips toward the floor (b). Pause, then press through your heel to return to start. That's one rep. Do eight to 12, then repeat on the other side.

Exercise 4 Plank Shoulder Taps

Get into a pushup position with your hands shoulder-width apart on the floor and your shins resting on top of the ball (a). Keeping your hips square to the floor, lift your right hand and tap your left shoulder (b). Return to start and repeat with the other arm. Continue alternating for a total of 26 reps.