No matter which variations you follow, crunches have the advantage over sit-ups of being able to better target abdominal muscles. "Because the movement is smaller, you can control momentum more," ...

Bicycle Crunch This exercise targets both the upper ... muscles while working the hip flexors and lower back. In a seated position, lift your legs and lean back, forming a V shape.

"Laying on your side as you do crunches will also target your oblique muscles," says Hess. Lifting your head and shoulders to one side or the other or engaging in bicycle crunches by involving ...