The crunch is one of the most popular abdominal exercises. It involves the entire abs, but primarily it works the rectus abdominis muscle and also works the obliques. It allows both building six-pack abs, and tightening the belly.
An approved crunch begins with you lying down, one knee bent, and hands positioned beneath your lower back for support. "Do not hollow your stomach or press your back against the floor", McGill says. Gently lift your head and shoulders, hold briefly and relax back down.
In a crunch, unlike a sit-up, the lower back stays on the floor. This is said to eliminate any involvement by the hip flexors, and make the crunch an effective isolation exercise for the abdominals.
- Reynolds, Gretchen (17 June 2009). "Is Your Ab Workout Hurting Your Back?". Well. The New York Times.
- Baker, Cameron. "Are Sit Ups Bad for You? The U.S. Military Seems to Think So…". www.ISSAonline.edu. Retrieved 17 October 2018.
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