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A pull-up is a variety of upper-body compound pulling motions for the purpose of exercise.
The most popular current meaning refers to a closed-chain bodyweight movement where the body is suspended by the arms, gripping something, and pulled up with muscular effort. As this happens, the wrists remain in neutral (straight, neither flexed or extended) position, the elbows flex and the shoulder adducts and/or extends to bring the elbows to or sometimes behind the torso.
A traditional pull-up relies on upper body strength with no swinging or "kipping" (using a forceful initial movement of the legs in order to gain momentum). The exercise often targets the latissimus dorsi muscle in the back along with many other assisting muscles.
Earlier meanings 
In past decades, a pull-up also included open-chain pulling exercises done with a barbell. These exercises are now more popularly known as the bent-over row (in the 50s) and upright row (in the 70s)
The name refers to pulling up one's body. It can be done with the hands facing any directions, from prone to supine.
Some have associated a "pull-up" with utilizing an overhand (pronated, palms facing away) grip. This includes by the Boy Scouts of America, Guinness World Records and recordholders.org. Organizations such as the United States Marine Corps however, see pull-ups as both the overhand and underhand grips.
A "chin up" is named after either bringing the chin up to touch the bar, or alternatively, bringing it up and over the bar. As this is more easily done with a supinated grip, chin-ups are commonly associated with doing pull-ups with an underhand (supinated, palms facing forward) grip.
Variations of pull ups, beyond being named for their grip, can also be named based on how high the body rises, by naming it after the body part that either comes into contact with or passes over the top of the bar. A "chest-up" or "sternum-up" for example, indicates that the chest or sternum meets the bar, requiring extra scapular adduction and depression.
The pull-up as a physical test 
Pull up tests in armed forces 
Pull ups are one of the best ways to measure the upper body strength of the "pulling muscles". They are commonly used by armed forces, such as the United States Marine Corps, as a vital way to determine strength among servicemembers.
Pull ups are also used as part of military test in places such as Singapore, where the IPPT for National-Service men is used. It is also used in the NAPFA test for male students above the age of 14.
This is determined by the amount of good form reps that can be done, commonly 20 to 25 pull ups in a row is the standard of perfect score in most of the physical condition tests and the minimum value is 3 full pull ups. This test is usually a non-timed event.
Pull-ups (including chins) can be done with a supinated, neutral or pronated grip. Grips may match each other or be different. Grips may also rotate throughout the movement, such as by doing them on rings or rotating handles. The range of motion used by trainers can vary. The fullest possible range is with straight arms overhead (elbow directly above shoulder), to pulling when the arms are at the sides (elbow directly below shoulder). People sometimes only train portions, such as avoiding locking out the arms at the bottom, or stopping when the head/chin/neck touch the bar. Positions within the range are also trained isometrically, as in flexed-arm and straight-arm hangs for time.
The width of the grip may also differ. When grabbing and holding the bar during the pull-up, the hands can be apart at shoulder-width, but also go beyond that. This will make the pull-up more difficult, but also limit the range of motion when compared to the shoulder-width grip.
Muscles used 
Pull ups primarily target the latissimus dorsi.
Pull ups also work the brachialis and brachioradialis in the arms. These muscles are located near the elbow, and help move the forearm. The biceps brachii, or simply biceps, cross the elbow and shoulder joints and work to flex the elbow joint during pull ups. =
Pull ups work on the teres major, a small muscle at the back of the shoulder blade. The nearby rhomboids, which connect the spine to the shoulder blade, play a part in pull ups and related exercises. Pull ups also work on the trapezius along the spine and shoulder, and the levator scalpulae along the side of the neck. These muscles work to elevate and move the shoulder blade, and are sometimes called the "shrugging muscles." The deltoid, which is used in all side lifting movements, and which stabilizes the upper arm bones on the scapula, also comes into play.
Abdominal muscles 
Your abdominal muscles stabilize your entire torso and help generate force to lift you up. They prevent your spine from rounding to compensate strength and injury. These stabilizers include the transversus abdominus, which is like a corset that surrounds your spine and organs, diaphragm, and other deep muscles near the spine. The outer abdominal muscles, including the rectus abdominus and external and internal obliques, function as secondary support for the stabilizing abdominal muscles.
Pelvic floor 
Like the abdominal muscles, the pelvic floor muscles hold your organs up within the body cavity and stabilize your pelvis and legs during pull-ups. Without proper hip stabilization, your legs and pelvis would move around as you pull, causing instability and decreasing your ability to perform a pull-up well.
Hands and forearms 
The hands receive a very challenging effort by holding the overall bodyweight improving the strength of the fingers and the forearms muscles creating a strong isometric contraction in this muscle groups.
List of some variations 
Standard dead-hang pull up is grasped with an overhand/underhand/alternative-hand grip. Then the body is pulled up until the chin clears the bar, and finished by lowering the body until arms and shoulders are fully extended. Stricter standards would only consider a full repetition to be one in which the elbows pass behind the coronal plane.
Weight is added using a dipping belt, or grasping a dumbbell with the feet, or weight vest/shorts
The chin is dropped forward through cervical flexion. The goal of the pull-up is to touch the bar with the back of the neck.
A one arm pull-up is performed by grasping the bar with only one hand while pulling up. This is difficult due to the considerable strength required.
An easier version of the one arm pull-up: a pull-up where one hand grips the other arm just below the wrist.
A pull-up staying as close as possible to one side; typically the arm doing the majority of the work is alternated each repetition.
An easier version where the body is bent dynamically to help propel the athlete upward. The hips swing first forward and then back as the legs swing forward. Finally, the legs swing downward again, pushing the torso upward. The fastest version where the head follows an elliptical path, moving backward at the bottom of the motion and forward at the top, is sometimes called a butterfly pull-up.
A pull-up with a longer range of motion, finishing with the bar touching the sternum.
A pull-up with a maximal range of motion, transitioning to a dip. Generally the initial pull-up uses an overhand grip to make the switch easier and is more explosive in order to take advantage of momentum from the first half of the exercise to aid in the second half.
Sometimes called an "Australian pull-up", "reverse push-up", "inclined pull-up" or "inverted row", this is performed with the bar 2 to 3 feet off the floor. The user lies on the ground under the bar, face-up, and grasps the bar with extended arms. The exercise is performed by pulling the chest up to the bar. The body is held in a rigid plank position while the heels remain on the floor. "Supine" refers to the body being face-up, not to the grip: supine rows can be done with prone, neutral or supinated hands.
One hand is placed in the overhand (pronated) position and the other is placed in the underhand (supinated) position to provide variation on the elbow flexors used.
See also 
|Wikimedia Commons has media related to: Pull-ups|
- Eva teaches the kipping pull-up at crossfit.com
- Bob Hoffman's Daily Dozen, published 1958. Exercise 8 on page 10.
- MuscleMag International 70s insert: "How to Increase Your Muscular Bulk and Strength" page 8/9
- Boy Scouts of America: illustration
- Guinness World Records, #1(pronated grip) must be used.
- recordholders.org, recordholders.org "makes a difference between" pull-ups and chin-ups according to grip.
- USMC fitness PDF Chapter 2: "a command will not mandate that Marines must use the overhand grip when executing pull-ups or flexed-arm hang" - May 10, 2002
- "Pull-up". acefitness.org. American Council on Exercise. Retrieved 27 March 2011.
- Pull-ups, American Council on Exercise
- United States Marines fitness guide that describes pull ups and how they can be done with a supine or prone grip
- Specific Guidelines Pack for "Heaviest Weighted Pull-up" by Guinness World Records.
- World record holders for Pull-ups and Chin-ups
- Swiss Pull-up Association
- Pull-up (neutral grip)
- Close Grip Chin-up
- Underhand Chin-up
- Wide Grip Chin-up (assisted)
- Weighted Pull-up
- Weighted Chin-up
- Weighted Pull-up (neutral grip)
- Weighted Close Grip Chin-up
- Weighted Underhand Chin-up
World Records (pronated grip) 
Guinness World Records 
- Most pull ups in one hour - 1,009 by Steffan Hyland (UK) 1 Aug 2010[dead link]
- The heaviest weighted pull up - 206.2 lbs by Steven Proto (USA) 9 July 2011
- Most Pull-ups in 3 mins - 100 Ngo Xuan Chuyen (VIE) 1988
- Most pull-ups in 30 mins - 543 Stephen Hyland (GBR)5 Jul 2010
- Most pull-ups in 6 hours - 2,456 Guy Schott (USA) 28 April 2007
- Most pull-ups in 24 hours - 3,165 Jason Armstrong (USA) 30 May 2010
- Heaviest weighted pull-up total - 402 lbs Steven Proto (USA) 28 April 2011
- Most pull-ups with a 45 lb plate - 18 Damien Longley (USA) 28 March 2011