3. They can create poor posture.
Crunches reinforce bad habits that result in poor posture. Many people unconsciously “tuck their butt under” and “hold in their abs” as a result of too much bad ab training.
Again, this reinforces conditioning that disrupts the natural curves of the spinal. The end result to all this “ab strengthened” a really STRONG bad posture.
And since the whole body is connected: Tucked bottoms result in flattened spinal curves which usually bring the shoulders slumped downward, the head forward, and starts to slowly work on that “old lady hump” in the back that nobody wants.
You can always tell when someone does too many crunches almost immediately by their posture alone.
4. They over-focus on surface muscles instead of deep core muscles.
Crunches really zone your surface ab muscles.
While it’s true that these are your “six pack” muscles, they are not the most important muscles for true core strength. You can have very “strong abs” and still end up with poor core support.
If all you care about is how your stomach looks, by all means, keep crunching away.
But if you want real strength that supports the body in motion (and is critical for living a pain-free life), go deeper and work your inner abs.