An abdominal exercise performed lying on your back, lifting your shoulders and upper back off the ground by contracting your abs. It's a more controlled movement than a full sit-up.
From the sound made during the exercise - the 'crunching' of abdominal muscles. The term became popular in the 1980s fitness boom, distinguishing this targeted ab exercise from traditional sit-ups.
The crunch was revolutionary because it isolated the abs without straining the lower back like sit-ups do! Research in the 1990s showed that crunches activate the rectus abdominis 64% more effectively than sit-ups while being much safer for the spine.
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