Ab crunches seem to be taught by most trainers. You have to be careful with crunches. Crunches work your rectus adominus which is the muscle the runs vertically across your stomach.
It's crucial to work your lower back as much as you work your rectus adominus or you'll cause problems with your back.
The spine has a curve to it called the lordosis. It's very important to have that curve. It helps support the weight your spine has to carry.
If your rectus adominus muscle is stronger than your lower back muscles it will take away that necessary curve in your back. You can do too many crunches if you aren't also doing exercises for your lower back!
It's important to have a well rounded strength training program. My strength training DVDs offer well balanced routines.
My goal is to train your body to be healthy and strong. Check out my DVDs on www.getrealfit.org
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