Here's how to do it right.
1. Crunch on an Exercise Ball
Sit on the exercise ball with your feet flat on the floor.
Let the ball roll back slowly and lie back until your thighs and torso are parallel with the floor.
Contract your abdominals raising your torso to no more than 45 degrees.
To work the oblique muscles, make the exercise less stable by moving your feet closer together.
2. See More of the Best Abdominal Exercises
See the full list of the best and worse ab exercises.