In an article in today's New York Times, it was written that abdominal crunches are bad for the spine. If you do them as I have described in an earlier blog post that you can find by searching, your spine will be [mostly] straight and you do not have to worry about hurting it. However, I did find the information in this article
http://well.blogs.nytimes.com/2009/06/17/core-myths/#comments useful, and I loved a Swiss Ball exercise.
Here it is:
Place your forearms and elbows on a Swiss Ball. Your body is straight behind you and steady yourself on the balls of your feet. Now stir the Swiss Ball clockwise and then counterclockwise. Do it each way for 2.5 minutes. Rest. Repeat until you cannot do it anymore. Then stand up and reach up to stretch your abdominal muscles. Lie down and hug your knees to stretch your lower back. You will find that I added some variation and stretching to the exercise.
Disclaimer: None of the above information can be taken as a substitute for advice from a medical professional such as a physician.
My third book, Pocket Guide to Fitness, is available on www.louizapatsis.com, http://www.authorhouse.com, www.bn.com and http://www.amazon.com. If you look up my name on those Web sites, you will find my other books The Boy in a Wheelchair and Life, Work and Play: Poems and Short Stories.