Crunches are definitely safer than sit-ups, but, as I understand it, they still exclusively exercise one muscle (the rectus abdominis) and one muscular action (torso flexion, bringing your shoulders and pelvis closer together).
Which a) most people don't need to work*, and b) will badly screw up your posture and thence your back if you don't balance it out with exercises that extend the back (if you think about it, a crunch consists of repeatedly and forcefully bringing your back into a slouched/hunched position).
So: you don't need to do crunches, and exercises like planks which work all the muscles needed to stabilize the spine (and also teach you how to find and hold that neutral position, which is key to all sorts of other exercises, whether that's push-ups or deadlifts) are going to be more useful and more effective.
*Exceptions would be people like mixed martial artists and anyone else who does a grappling sport, where you may need to headlock your opponent and force their head down.
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branchandroot
In which I tl;dr, because I geek out about this stuff
Date: 2011-08-19 11:02 am (UTC)Which a) most people don't need to work*, and b) will badly screw up your posture and thence your back if you don't balance it out with exercises that extend the back (if you think about it, a crunch consists of repeatedly and forcefully bringing your back into a slouched/hunched position).
So: you don't need to do crunches, and exercises like planks which work all the muscles needed to stabilize the spine (and also teach you how to find and hold that neutral position, which is key to all sorts of other exercises, whether that's push-ups or deadlifts) are going to be more useful and more effective.
*Exceptions would be people like mixed martial artists and anyone else who does a grappling sport, where you may need to headlock your opponent and force their head down.