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," ...

The reverse crunch is a simple core exercise that targets those hard-to-hit lower abs — without straining your neck and back.

When done with proper form, squats tone your quadriceps, hamstrings and glutes. Learn how to do a squat, plus squat ...

The same can be said of long-standing resistance training exercises and bodyweight movements like pull-ups, squats, push-ups and sit-ups. Crunches are another enduring bodyweight exercise.