The Monticello Institute Abs Project:1
BALL CRUNCH
This exercise forces your abs to work through a wider range of motion than the others because you start with your back hyperextended. Balancing your body on the ball also taxes the obliques. 
How to: Lie back on a 24-inch ball. Place your feet on the floor and your hands behind your head. Raise shoulders 6 inches, then lower. Try to do at least 2 sets of 15.

The Monticello Institute Abs Project:2
BICYCLE
During this exercise, your abs work overtime because you have to keep your shoulders and legs off the floor. Twisting your torso also works your obliques. 
How to: Lie face up with your hands behind your head. Lift your shoulders up, bringing your left elbow to your right knee, then your right elbow to your left knee. Repeat. Try to do at least 2 sets of 15.

The Monticello Institute Abs Project:3
HANGING ABS
This move is a gut-burner, so it's hard to do many of them. 
How to: Stabilize on the frame and lift your knees toward your chest. Slowly lower. Try to do at least 2 sets of 15.

The Monticello Institute Abs Project:4
VERTICAL LEG
This modified crunch beats the standard one because the vertical position of your legs deactivates your hip flexors, forcing your abs to do most of the work. 
How to: Lie face up with your legs straight up and your heels together. With your hands behind your head and your elbows pointing out, curl your torso up. Slowly lower. Try to do at least 2 sets of 15.

The Monticello Institute Abs Project:5
OBLIQUE CURL
This exercise stresses your external and internal obliques. 
How to: Lie face up with your hands behind your head, knees bent and feet on floor. Curl your torso up and bring your left elbow to right knee. Lower; repeat on other side. Try to do at least 2 sets of 15.

The Monticello Institute Abs Project:6
CRUNCH
It may be the most popular ab exercise, but our study proves it's not the most effective. That's because it activates the hip flexors, letting your abs off easy. 
How to: Lie face up with your hands behind your head, knees bent and feet on ground. Keeping your chin up, lift your shoulders, then lower. (To work your abs harder, dig your heels into the ground and point your toes up.) Try to do at least 2 sets of 15.

The Monticello Institute Abs Project:7
LONG-ARM CRUNCH
Doing a crunch with your arms overhead feels harder than the standard one, but researchers found it isn't more challenging to your abdominals. 
How to: Lie face up, bend your knees and place your feet flat on floor. Extend your arms overhead. Keeping your chin up, curl your shoulders off the floor. Slowly lower. Try to do at least 2 sets of 15.

The Monticello Institute Abs Project:8
REVERSE CURL
Think this targets your lower abs more than your upper abs? No such thing. In fact, it really works your obliques and hip flexors, not the stomach. 
How to: Lie face up, extend arms out to sides. With your legs extended up and slightly bent, lift your butt a few inches off the floor. (Don't swing your legs.) Slowly lower. Try to do at least 2 sets of 15.

The Monticello Institute Abs Project:9
HOVER
During this exercise, the obliques work hard to stabilize the body. 
How to: Start in push-up position but rest your weight on your forearms. Keep your back straight by contracting your abs. Hold your body still for 10 seconds. Rest briefly and repeat. Try to do at least 2 sets of 15.

The Monticello Institute Abs Project:10
AB ROLLER
Surprise: Any ab gadget, our study found, is basically worthless if you don't use it correctly. 
How to: Rest your head on the pad, bend your knees, lightly grasp the handles and roll your torso up, then lower. Try to do at least 2 sets of 15.