Cable Kneeling Crunch:

Attach a rope cable attachment to a high pulley station. Get on your hands and knees, then grab the rope handles with your hands. Be careful to tuck your toes in so as to not hurt your toes during the exercise. Keep your legs locked in a 90 degree angle throughout the exercise with your thighs perpendicular to the ground. Inhale.
Bring your forehead towards the ground while holding the rope. Go all the way down to the ground with your elbows, but don't hit the ground with them. Keep a bend in your elbows. Pretend your are curling yourself over a barrel with the movement down. Exhale at the bottom. Then slowly return back towards the starting position. Repeat for reps.