This is a perfect exercise to give an extra challenge to your abs. I use a bench for this demonstration but you can also do this lying on an exercise mat. You will need one powerblock or dumbbell.
Lay flat on the surface with the dumbbell gripped in both hands. Move the weight behind your hand and slowly bring your hands up and crunch as you reach the weight toward your toes. Then raise your arms back up and move them behind your head again.