Crunches: Knees Up (abs)

Crunches: Knees Up keeps the legs elevated and hips flexed, which holds tension on the upper abs through the entire rep instead of letting it ease off between reps.

Lie on your back with your knees bent and lifted so your shins are roughly parallel to the floor. Curl your shoulders and upper back off the floor toward your knees, then lower back down slowly without letting your feet drop.