Stop doing sit-ups. Especially if you're head is flying forward, your neck is straining and your back hurts more than your abs!

Basic Plank

Incline Plank - Marching Legs

The most effective abdominal exercise is the plank - an isometric exercise, requiring you to hold your muscles in a contracted position to maintain stability. When you have mastered the basic plank (you may need to start on your knees), you can try these modifications to target different muscles and add a new level of challenge to your abs routine. How long can you hold?

Leg Arm Extension

Plank with Row

Side Plank