For those of you who simply cannot give up your ab crunches (see post from Nov. 7), here is a safer version that avoids compression of the spine:
Start on your back with one leg straight and the other bent on the ground. Place your hands under your middle/lower back. This is to help you maintain a neutral spine. Notice how much your back presses into your hands; as you do the exercise the pressure should stay the same, the back should not press into the hands OR come away from them. Perform an abdominal brace (activate the abdominal muscles by bracing for a punch, but do not allow the back to move), then simply raise the head and shoulders off the ground. The movement is in the thoracic spine only, NOT in your neck or lower back region. Try to keep the abdominal brace and hold for 5 or 6 seconds. Do not hold your breath. Once you can do two sets of 12 in perfect form you can make it more challenging by lifting your elbows off the ground.
The pictures below are examples to avoid:
The picture above shows rounding of the cervical spine (the neck area) that you should avoid. Her chin is almost on her chest. For correct form imagine holding an orange under your chin; do not let it roll out, and do not make orange juice.
This picture shows the opposite incorrect neck position; his chin is pointed at the ceiling.
This picture shows the rounding of the lumbar spine (the lower back) that you should also avoid.