Crunch (exercise)
Encyclopedia
Abdominal exercise
Abdominal exercises are those that affect the abdominal muscles .-Usage:Abdominal exercises are useful for building the abdominal muscles...
s. It primarily works the rectus abdominis muscle
Rectus abdominis muscle
The rectus abdominis muscle, also known as the "six pack", is a paired muscle running vertically on each side of the anterior wall of the human abdomen . There are two parallel muscles, separated by a midline band of connective tissue called the linea alba...
.
Form
A crunch begins with lying face up on the floor with kneeKnee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...
s bent. The movement begins by curling the shoulder
Shoulder
The human shoulder is made up of three bones: the clavicle , the scapula , and the humerus as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The major joint of the shoulder is the glenohumeral joint, which...
s towards the pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
. The hands can be behind or beside the neck or crossed over the chest. Injury can be caused by pushing against the head or neck with the hands.
Alternatives
Crunch exercises may be performed on exercise balls. Weights may be used, typically held under the chin, to increase resistance. Increasing the distance will also increase the load on the abdominals due to leverage.The curl-up is taught by spine biomechanics
Biomechanics
Biomechanics is the application of mechanical principles to biological systems, such as humans, animals, plants, organs, and cells. Perhaps one of the best definitions was provided by Herbert Hatze in 1974: "Biomechanics is the study of the structure and function of biological systems by means of...
professor Dr. Stuart McGill, and he considers it to be a safer alternative to the crunch, which differs from the sit-up
Sit-up (exercise)
The sit-up is a strength training exercise commonly performed with the aim of strengthening the hip flexors and abdominal muscles. It begins with lying with the back on the floor, typically with the arms across the chest or hands behind the head and the knees bent in an attempt to reduce stress on...
. Dr. Stuart McGill has done extensive research on the effects of crunch exercises on the back, which can be especially harmful for those rehabilitating their backs from an injury.
The New York Times
The New York Times
The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...
Health blog
Blog
A blog is a type of website or part of a website supposed to be updated with new content from time to time. Blogs are usually maintained by an individual with regular entries of commentary, descriptions of events, or other material such as graphics or video. Entries are commonly displayed in...
referencing Dr. McGill in 2009 stated:
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.
Strength exercises such as sit-ups and crunches do not cause the spot reduction of fat. Achieving "six pack abs
Rectus abdominis muscle
The rectus abdominis muscle, also known as the "six pack", is a paired muscle running vertically on each side of the anterior wall of the human abdomen . There are two parallel muscles, separated by a midline band of connective tissue called the linea alba...
" requires both abdominal muscle hypertrophy
Hypertrophy
Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It should be distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number...
training and fat loss over the abdomen -— which can only be done by losing fat from the body as a whole.
Differences between a crunch and a sit-up
Unlike the sit-upSit-up (exercise)
The sit-up is a strength training exercise commonly performed with the aim of strengthening the hip flexors and abdominal muscles. It begins with lying with the back on the floor, typically with the arms across the chest or hands behind the head and the knees bent in an attempt to reduce stress on...
, in a proper crunch, the lower back stays on the floor. This is said to eliminate any involvement by the hip flexors
Hip flexors
In human anatomy, the hip flexors are a group of skeletal muscles that act to flex the femur onto the lumbo-pelvic complex, i.e., pull the knee upward....
, and make the crunch an effective isolation exercise for the abdominals. This is not true, because the psoas muscles are both hip flexors and trunk flexors, and works as a synergist to aid the rectus abdominis in the crunch.
In many cases, the hips will be pre-flexed to shorten the psoas muscles to lessen its involvement due to over-active insufficiency.
The difficulty of the crunch can be increased by lying on a declined bench and/or holding a weight on the chest or behind the head.
Variations
- The reverse crunch is a crunch done with the upper back on the floor and lifting the hips up instead.
- The twisting crunch is performed by lifting one shoulder at a time. More emphasis is placed on the obliquesAbdominal external oblique muscleThe external oblique muscle is the largest and the most superficial of the three flat muscles of the lateral anterior abdomen.-Structure:...
. - The bicycle crunch is a variation of the twisting crunch performed by bringing together alternating elbows and knees, resulting in a leg motion similar to pedaling a bicycleBicycleA bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....
. The bicycle crunch is the most effective in targeting the rectus abdominis and the obliquesAbdominal external oblique muscleThe external oblique muscle is the largest and the most superficial of the three flat muscles of the lateral anterior abdomen.-Structure:...
, according to a study done by the American Council on ExerciseAmerican Council on ExerciseThe American Council on Exercise is a nonprofit fitness certification and education provider.Established in 1985, ACE now operates as a full-service entity with a staff of more than 40...
. - The Thai crunch is performed by hitting the stomach after full contraction. This variation is used by Muay ThaiMuay ThaiMuay Thai is a combat sport from Thailand that uses stand-up striking along with various clinching techniques. It is similar to other Indochinese kickboxing systems, namely pradal serey from Cambodia, tomoi from Malaysia, lethwei from Myanmar and muay Lao from Laos...
fighters to condition the core to take hits from punches or knees. - The cable crunch is performed while kneeling upright by curling the body to pull down on a cable machineCable machineA cable machine is an item of equipment used in weight training or functional training. It consists of a rectangular, vertically-oriented steel frame about 3 metres wide and 2 metres high, with a weight stack at each end. The cables that connect the handles to the weight stacks run through...
. The hips are kept motionless. - The dragon flag (thought by some to have been created by Bruce LeeBruce LeeBruce Lee was a Chinese American, Hong Kong actor, martial arts instructor, philosopher, film director, film producer, screenwriter, and founder of the Jeet Kune Do martial arts movement...
) or simple "flag" popularized by Sylvester StalloneSylvester StalloneMichael Sylvester Gardenzio Stallone , commonly known as Sylvester Stallone, and nicknamed Sly Stallone, is an American actor, filmmaker, screenwriter, film director and occasional painter. Stallone is known for his machismo and Hollywood action roles. Two of the notable characters he has portrayed...
in his movie Rocky IVRocky IVRocky IV is a 1985 American film written by, directed by, and starring Sylvester Stallone. It is the fourth and most financially successful entry in the Rocky franchise...
), called "dragon" after one of Bruce Lee's nicknames, "little dragon". Begin lying horizontal on a bench. The arms are used to hold the underside of the bench to anchor the shoulders to it to prevent rolling forward. The rest of the body inferior to the scapulae is then pulled from the bench. Beginning with legs flexed, the legs can be extended slowly to increase the difficulty of the movement (and tension on the core muscles) due to moving the weight further from the levers. Throughout the movement the knee and hip joints are meant to remain locked in full extension while movement occurs in the abdominal region.