Well, here's some good news: You really shouldn't be doing them, anyway
Turns out that crunches can put undue stress on your spine and actually be bad for you. The back of your spine is full of nerves - and these nerves can be damaged when crunches strain your back at its weakest point. The repetitive movement of bending and flexing over time can cause a disk bulge or herniation. And if you've never experienced one of these, trust me, you don't want to. The pain does not just stay in your back, but can radiate down your leg and even cause weakness and tingling.
But wait a minute - before you start celebrating the end of the dastardly crunch, you should know this: abdominal muscles are really important and they do need to be strong. Strong abs help keep your back supported and feeling good. They also help you to perform a lot of everyday activities, like opening a heavy door, and create a strong foundation for just about any other movement. So, it's important to work your "core" - the muscles that run the length of your trunk and torso.
Showing off a six-pack in a bikini may be in the past, but that shouldn't stop us from aiming for abs of steel - for lots of other important reasons!
Click here to learn more about flexibility and your core.
And for a slide show of effective core exercises, check this out.