http://AskTheTrainer.com/best-ab-exercises.html Personal Trainer Mike Behnken, MS, NASM-CPT-PES, CSCS Crunches are a simple isolation exercise for your rectus abdominis. If you really want full benefit out of the crunch and work your abs, not just your ab (rectus abdominis) do 2 things for the duration of your set of crunches. 1. Draw in your core. Squeeze your belly button down towards your spine. This is activating the other abdominal ( the transverse abdominis or core ) If you do not draw in your core, you may build a bloated looking distended set of abs. 2. Contract Your Glutes Squeezing your glutes is Very important if you want to isolate your abs completely. The hip flexors cannot interfere with your abdominal contraction if the antagonist muscle (gluteus maximus) is contracted. Crunches will not burn fat off your mid section. If you would like to burn the fat which is covering your abs, you need to have a clean, healthy diet, drink plenty of water and do your cardio exercise. http://AskTheTrainer.com/best-cardio-exercises.html