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The crunch or curl-up is an abdominal exercise that works the
The
rectus abdominis muscle
The rectus abdominis muscle, () also known as the "abdominal muscle" or simply better known as the "abs", is a pair of segmented skeletal muscle on the ventral aspect of a person's abdomen. The paired muscle is separated at the midline by a ba ...
. It enables both building and defining "six-pack" abs and tightening the belly. Crunches use the exerciser's own body weight to tone muscle and are recommended by some experts, despite negative research results, as a low-cost exercise that can be performed at home. Crunches are less effective than other exercises such as planks and carry risk of back injury.
Form
The biomechanics
Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to Organ (anatomy), organs, Cell (biology), cells and cell organelles, using the methods of mechani ...
professor Stuart McGill was quoted in ''The New York Times
''The New York Times'' (''NYT'') is an American daily newspaper based in New York City. ''The New York Times'' covers domestic, national, and international news, and publishes opinion pieces, investigative reports, and reviews. As one of ...
Health'' blog
A blog (a Clipping (morphology), truncation of "weblog") is an informational website consisting of discrete, often informal diary-style text entries also known as posts. Posts are typically displayed in Reverse chronology, reverse chronologic ...
as stating:
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.Research has shown that both sit-ups and crunches are mediocre strength-building exercises and have injured many people. In a crunch, unlike a
sit-up
The sit-up is an abdominal endurance training exercise to strengthen, tighten and tone the abdominal muscles. It is similar to a curl-up (that targets the rectus abdominis and also works the external and internal obliques), but sit-ups have a ...
, the lower back
Lower may refer to:
* ''Lower'' (album), 2025 album by Benjamin Booker
*Lower (surname)
*Lower Township, New Jersey
*Lower Receiver (firearms)
*Lower Wick
Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is sit ...
stays on the floor. This is said to eliminate any involvement by the hip flexors
In anatomy, flexor is a muscle that contracts to perform flexion (from the Latin verb ''flectere'', to bend), a movement that decreases the angle between the bones converging at a joint. For example, one's elbow joint flexes when one brings the ...
, and make the crunch an effective isolation exercise for the abdominals.
World records
Sirous Ahmadi has the record of doing over 20000 crunches in under 5 hours on May 11, 2024. In 2018, John Peterson from the US did 6,774 crunches in an hour and in 2021, he did a total of 13,994 crunches in two hours.See also
*Plank (exercise)
The plank (also called a front hold, hover, or abdominal bridge) is an isometric exercise, isometric core (anatomy), core strength exercise that involves maintaining a position similar to a push-up.
Form
The most common plank is the forearm p ...
* Sit-up
The sit-up is an abdominal endurance training exercise to strengthen, tighten and tone the abdominal muscles. It is similar to a curl-up (that targets the rectus abdominis and also works the external and internal obliques), but sit-ups have a ...
References
External links
Bodyweight exercises Strength training Physical exercise {{Health-stub