WordNet

(physiology) a shortening or tensing of a part or organ (especially of a muscle or muscle fiber) (同)muscular_contraction, muscle_contraction
the act of decreasing (something) in size or volume or quantity or scope
a word formed from two or more words by omitting or combining some sounds; "`wont is a contraction of `will not"; "`oclock is a contraction of `of the clock"
related by an isometry
having equal dimensions or measurements (同)isometrical
of a crystal system characterized by three equal axes at right angles
of or involving muscular contraction in which tension increases while length remains constant
muscle-building exercises (or a system of musclebuilding exercises) involving muscular contractions against resistance without movement (the muscles contracts but the length of the muscle does not change) (同)isometric_exercise

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〈U〉〈C〉(…の)収縮,短縮《+『of』+『名』》 / 〈U〉(通貨・資金・支出などの)縮小,節減《+『of』+『名』》 / 〈U〉(いやなこと・よくないことを)身に負うこと,(悪習などが)身につくこと《+『of』+『名』》 / 〈C〉陣痛

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/11/11 03:47:25」(JST)

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Isometric exercise or isometrics are a type of strength training in which the joint angle and muscle length do not change during contraction (compared to concentric or eccentric contractions, called dynamic/isotonic movements). Isometrics are done in static positions, rather than being dynamic through a range of motion.^[1]

Overcoming versus yielding

In an overcoming isometric, the joint and muscle work against an immovable object. In contrast, in a yielding isometric, the joint and muscle are held in a static position while opposed by resistance.

In the context of the bench press, an example of a yielding isometric would be holding the bar at a given place even though it could be pressed higher, and an overcoming isometric would be pressing the bar up into the safety guards of a squat cage that prevent pushing the bar any higher.

The distinction is that in a yielding isometric, one is pressing roughly the exact amount of pressure needed to negate the resistance, neither dropping or lifting it. Whereas in an overcoming isometric, one can be exerting more force and simply unable to move it. The yielding wavers slightly into concentric and eccentric actions due to inexact control, whereas the overcoming isometric is more purely isometric and can involve more variation in the force used, since one can press harder without the bar moving.

Unweighted

In overcoming isometrics, subjects can safely do 100 percent effort, and continue with 100 percent available effort as strength is depleted, allowing longer time under (maximum volitional) tension.^{[citation needed]} This is thought by experts such as Ken Hutchins^[2] and Drew Baye to be best for building muscle.^{[citation needed]} However, subjects depend on a subjective perception of effort and progress, unless an expensive metered system is available.^{[citation needed]}

Weighted

Yielding isometrics allow measurable progress. Free-weight enthusiasts tend to believe the "back pressure" of real weight is superior for building strength, possibly triggering a productive "fight or flight" response.^{[citation needed]} However, the extremely heavy weights needed by advanced subjects can be an inconvenience, and present a risk of injury.

Definition

An isometric exercise is a form of exercise involving the static contraction of a muscle without any visible movement in the angle of the joint. The term "isometric" combines the Greek words "Isos" (equal) and "metria" (measuring), meaning that in these exercises the length of the muscle and the angle of the joint do not change, though contraction strength may be varied.^[3] This is in contrast to isotonic contractions, in which the contraction strength does not change, though the muscle length and joint angle do.

Isometric resistance

Resistance in isometric exercises typically involves contractions of the muscle using:

The body's own structure and ground
Structural items (e.g., pushing against a fence)
Free weights, weight machines, or elastic equipment (e.g., holding a weight in a fixed position)
Pressure-plate-type equipment that has a digital display of maximal force.

Depending on the goal of the exercise, the exertion can be maximal or sub-maximal.

History

Isometric exercises are thousands of years old,^{[citation needed]} with examples listed from the static holds in certain branches of yoga or oriental martial arts.

Isometric exercises were first brought to the modern public's attention in the early days of physical culture, the precursor to bodybuilding. Many of the great bodybuilders of the day incorporated isometric exercises into their training regimens.^[4]

Many of today's training protocols incorporate isometric exercises, which are often made into parts of normal, isotonic exercises. For example, during a set of seated rows, a subject can hold their position when the handles are closest to their chest in order to "squeeze" the muscle, in an effort to further strain the muscle.

Contrary to popular opinion, The Charles Atlas "Dynamic tension" Course did not use any true isometric exercises, but rather dynamic self-resistance, that is, pitting one muscle group against another and calisthenics.

Medical uses

Isometric exercises can also be used at the bedside to differentiate various heart murmurs; the murmur of mitral regurgitation gets louder^[5] as compared to the quieter murmur of aortic stenosis.^[6] They can also be used to prevent disuse syndrome in a limb that has been immobilized by a cast following a fracture.

Seated isometric exercises

One benefit of isometric exercise is that it can be done pretty much anywhere using your own body weight. According to "Sit Sense", a book on seated exercises, you can get a significant workout with seated isometric exercises and significantly lower your blood pressure. Seated isometric exercise is ideal for geriatrics or rehabilitation.

Comparison with dynamic exercises

While isometric training increases strength at the specific joint angles of the exercises performed and additional joint angles to a lesser extent, dynamic exercises increase strength throughout the full range of motion.^[7] More recent research has confirmed the finding that every skill has a specific strength component that must be practiced with the skill itself.^{[citation needed]} When a subject performs any sort of dynamic resistance training, many other muscle groups work isometrically. For example, the muscles of the core in a squat, the hamstrings in a stiff leg deadlift, the lats or upper back in a wide grip chin-up, and the muscles of the forearms in a dumbbell or barbell biceps curl all employ forms of isometric exercise on peripheral muscle groups.

NASA studies

NASA has researched the use of isometrics in preventing muscle atrophy experienced by astronauts as a result of living in a zero gravity environment. Isometrics, muscle lengthening and muscle shortening exercises were studied and compared. The outcome showed that while all three exercise types did indeed promote muscle growth, isometrics failed to prevent a decrease in the amount of contractile proteins found in the muscle tissue. The result was muscle degradation at a molecular level. As contractile proteins are what cause muscles to contract and give them their physical strength, NASA concluded that isometrics may not be the best way for astronauts to maintain muscle tissue.^[8]

References

^ "Are isometric exercises a good way to build strength?". Mayoclinic.com. Archived from the original on 2014-06-01. Retrieved 2014-06-01.
^ Hutchins, Ken. Super Slow: The ULTIMATE Exercise Protocol. Casselberry FL: Super Slow Systems, 1989, 1992. ISBN 0-9633199-0-6
^ "Article on static strength training". Sport-fitness-advisor.com. Retrieved 2014-02-26.
^ "Strength Training - Isometric Exercise". SPMESSENGER.com. Archived from the original on 2008-01-29. Retrieved 2008-11-10.
^ Ching, W. "Evaluation of Cardiac Murmurs in the Clinic Setting". University of Chicago. Retrieved 2008-01-10.
^ Cassidy J, Aronow WS, Prakash R (1975). "The effect of isometric exercise on the systolic murmur of patients with idiopathic hypertrophic subaortic stenosis". Chest 67 (4): 395–397. doi:10.1378/chest.67.4.395. PMID 1168115.
^ Lindh M (1979). "Increase of muscle strength from isometric quadriceps exercises at different knee angles". Scand J Rehabil Med 11 (1): 33–6. PMID 419396.
^ Barry, PL; Phillips, T (2004-10-12). "Why do Workouts Work?". NASA. Retrieved 2008-01-10.

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English Journal

Prolonged infrapatellar tendon vibration does not influence quadriceps maximal or explosive isometric force production in man.

Fry A1, Folland JP.
European journal of applied physiology.Eur J Appl Physiol.2014 Aug;114(8):1757-66. doi: 10.1007/s00421-014-2904-z. Epub 2014 May 21.
PURPOSE: The influence of muscle/tendon vibration on maximal muscle performance is unclear. This study examined the effect of a prolonged tendon vibration stimulus on maximum voluntary contraction (MVC) and explosive voluntary contraction (EVC) performance.METHODS: Eighteen young healthy males (nine
PMID 24846679

Interdependence of torque, joint angle, angular velocity and muscle action during human multi-joint leg extension.

Hahn D1, Herzog W, Schwirtz A.
European journal of applied physiology.Eur J Appl Physiol.2014 Aug;114(8):1691-702. doi: 10.1007/s00421-014-2899-5. Epub 2014 May 14.
PURPOSE: Force and torque production of human muscles depends upon their lengths and contraction velocity. However, these factors are widely assumed to be independent of each other and the few studies that dealt with interactions of torque, angle and angular velocity are based on isolated single-joi
PMID 24819448

Japanese Journal

Frequent alternate muscle activity of plantar flexor synergists and muscle endurance during low-level static contractions as a function of ankle position

TAMAKI Hiroyuki,KIRIMOTO Hikari,YOTANI Kengo,TAKEKURA Hiroaki
The journal of physiological sciences : JPS 61(5), 411-419, 2011-09-01
NAID 10029575805

Methodological Issues Related to Thickness-Based Muscle Size Evaluation

AKAGI Ryota,IWANUMA Soichiro,FUKUOKA Masato,KANEHISA Hiroaki,FUKUNAGA Tetsuo,KAWAKAMI Yasuo
Journal of physiological anthropology 30(4), 169-174, 2011-07-31
… area, thickness (the vertical distance from the upper end of the elbow flexors to that of the humerus) and width (the horizontal distance from the left to the right end of the elbow flexors) of the elbow flexors at levels from the reference site (60% of the upper arm length from the acromial process of the scapula to the lateral epicondyle of the humerus) to 5 cm distal to it were determined in 11 young men using magnetic resonance imaging, both at rest and during isometric elbow flexion at 30% of maximal voluntary contraction. …
NAID 10029137443