Slowly roll the spine forward from the chest to hips. A great way to increase the intensity of your abdominal training is to cross your arms over your chest and hold a small weight in tight to your chest. Remember, abdominal muscles, like other muscles, need change in intensity to stimulate growth now and then. Don't shy away from exercises that may push your abs to another level. Just be sure to have your lower back supported and perform the exercise with care.
Many people like to hold their hands behind their head when doing crunches.
Unfortunately, when they begin to strain there is a tendency to pull the head to get a bit more leverage. This puts extraordinary stress on the cervical vertebrae and can be dangerous. If you can't get used to putting your hands across your chest, touch your ears with your fingers. This will stop you from pulling on your head and allow for a more intense movement. Never hold your breath during ab training.