• Bicycle maneuver

• Captain's chair*

• Crunches on an exercise ball

• Vertical leg crunch

• Torso Track

• Long-arm crunch

• Reverse crunch

• Crunch with heel push

• Ab Roller

• Hover

• Traditional crunch

• Exercise tubing pull

• Ab Rocker

*Captain's chair: You need a piece of gym equipment to do this. In essence, you lift and lower your knees toward your chest while gripping handholds and pressing your back against a back pad.

Source: American Council of Exercise