I'm glad you are at least reading some stuff on this back subject, but most of the health information out there is complete @!%& and backwards.
The guy I cited is a PhD. He knows his stuff. ^^ The other people I rely on are trainers (usually with pretty decent educations, like a Masters or at least Bachelor's in their field) that train athletes that dead lift weights in excess of 600lbs, squats in excess of 800lbs, etc.
If you do what every major health "guru" or media source said you would be perplexed as to what the right way was because they are all saying something else.
This is true .. to an extent. But there are usually somewhat of a consensus on certain topics. And I'm usually looking at what people who say, train Olympic athletes or power lifters and such have to say. Like I said, most of them disagree on everything from rest period, how many reps, what weight, how fast you should lift, what exercises are best for hitting what area .. but almost none of them use crunches, or recommend them, and some even outright refuse to use them.
What works for one person doesn't always work for another. doing a sit up isn't a good exercise for someone who isn't thin or has back problems. That is fairly obvious.
People do lots of very dangerous and stupid things and yet still live just fine. Doesn't mean it's good advice nor does it say anything about its safety. The fact that Ozzy Osbourne is still alive is proof that some people are impervious to things that would kill us mere mortals.
I think most everyone in this thread is well under the age of 30. Doing crunches and sit-ups isn't going to hurt you .. now. It may never hurt you. But where it can hurt you is down the road. This isn't a "omg, I did crunches for a week and now my back is ruined thing" .. it's slow and gradual.
For everyone else? Who knows.. but its worked for dozens of years for many and that is all the evidence that is really needed to whether it is good (for a select people) to do, compared to another exercise.
Well, if that's what people want to base their decisions on, that's perfectly fine. People can do whatever the heck they want. ^^ But I'm looking at what the science says and from what I have read, it says that crunches can cause long-term problems, even in people with "healthy" backs that have no prior issues.
I have still yet to hear why anyone would want to bend their lower back like that. I mean, what activity would you do (unless you're a gymnast or something I guess) that would require you to bend your lower back in such a way? Try lifting something really heavy with your lower back bent like how it would be when doing a crunch .. okay, I'm kidding, don't actually do that because you'll hurt yourself.
Anyways, I think I've already posted about 5 or 6 times on this topic in this thread. I don't want to turn it into an abs debate. XD So, I'll leave it alone now.