Long Lever Crunches
Long lever crunches primarily work the upper abs and you need a bench or ball to do them. While lying flat on your back, prop your heels up on the bench and extend your arms straight behind your head and just above the floor. In a steady motion, raise your shoulders off the floor and move your torso forward. Squeeze your abs forcefully, slowly lower yourself back down and repeat. To increase the resistance, hold a weight plate or medicine ball in your hands.
Planks
Planks, which are yoga poses, require you to hold your body motionless and they work your whole abdominal area. While lying on your stomach, place your hands shoulder-width apart on the floor and feet together behind you. Steadily push your body off the floor, fully extend your arms and form a straight line from your heels to your shoulders. Feel your abs tightening up when you get into this position and hold until you feel fatigued. For a variation, place your forearms on the floor.
Knee Tucks
Knee tucks work your upper and lower abs and they require the use of a stability ball. After getting onto the ground on your belly, place your hands shoulder-width apart and prop your lower shins up on the ball. Steadily push yourself straight up into a plank position and roll the ball toward your head. Tuck your knees into your chest, hold for a second and extend your legs back out.
For a challenging variation, perform these with one leg at a time. With both versions, keep your back as straight as possible.
Lying Twists
Lying twists, which are also known as windshield wipers, work your obliques. While lying flat on your back, extend your arms out to your sides and raise your legs straight above you with your feet parallel to the ceiling. Keeping your upper body still, slowly lower your legs down to your right side and then left side. Move back and forth in a smooth and controlled motion.
To increase the intensity, wear ankle weights. For an easier variation, bend your knees 90 degrees. This exercise also works your lower back.
Moving Side Planks
Moving side planks target the obliques and they are variations of the basic side plank. After lying on your right side, stack your legs, prop your head up with your right hand and place your left hand on your hip. Push yourself up in a lateral direction until you have a straight line from your shoulders to feet. Slowly lower your hips toward the floor then lift them back up as high as possible, and repeat. After doing a set of reps, switch sides.
For a variation, extend your leg in the air every time you lift your body up. With either version, maintain straight alignment from your shoulders to heels.
Criss Cross
The criss cross is a Pilates move that works the entire stomach area. While lying flat on your back with your hands on the sides of your head, lift your legs, bend your knees 90 degrees and level your shins to the ground. Next raise your head and shoulders off the floor and move your opposite elbow and knee toward each other while extending one leg out straight. Quickly reverse this motion to work your other side and continue to alternate back and forth.