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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 isotonic movements). Isometrics are done in static positions, rather than being dynamic through a range of motion. The joint and muscle are either worked against an immovable force (overcoming isometric) or are held in a static position while opposed by resistance (yielding isometric).

Contents 1 Definition 2 Isometric resistance 3 History 4 Medical uses 5 Comparison with dynamic exercises 6 NASA studies 7 See also 8 References 9 External links

[edit] Definition

Isometric exercise is a form of exercise involving the static contraction of a muscle without any visible movement in the angle of the joint. This is reflected in the name; the term "isometric" combines the prefix "iso" (same) with "metric" (distance), meaning that in these exercises the length of the muscle does not change,^[1] as compared to isotonic contractions ("tonus" means "strain" in Latin) in which the contraction strength does not change but the joint angle does.

[edit] Isometric resistance

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

• the body's own muscle (e.g., pressing the palms together in front of the body)
• structural items (e.g., pushing against a door frame).
• free weights, weights machines or elastic equipment (e.g. holding a weight in a fixed position)
• pressure plate type equipment that has a digital readout of maximal force.

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

[edit] History

Isometric exercises are thousands of years old, with examples from the static holds in certain branches of yoga or Chinese martial arts.

Isometrics 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 regimes. Contrary to popular opinion, The Charles Atlas "Dynamic Tension" Course did not include any true isometric exercises, but rather Self-Resistance (that is: Pitting one limb against the other) and Bodyweight Calisthenics.^[2] which he learned from the "Conscious Evolution" course of Alois P. Swoboda.^[3] Isometrics fell out of favor as it was discovered that many of the principal advocates were using anabolic steroids to enhance their gains.^[4]

Today many new training protocols exist incorporating isometrics once again. Isometric exercises are often made into parts of normal, isotonic exercises. For example, during a set of rows, some people 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.

[edit] 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]

[edit] Comparison with dynamic exercises

Isometric exercises have some differences in training effect as compared to 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]. Generally speaking however, people who train isometrically don't train through a full range of motion as the strength gained at the training joint angle is where they require it. While dynamic exercises are slightly better than isometric exercises at enhancing the twitch force of a muscle, isometrics are significantly better than dynamic exercises at increasing maximal strength at the joint angle.^[8] Flexibility may be increased when isometrics are performed at joint range of motion extremes. These isometric contractions recruit muscle fibers that are often neglected in some dynamic exercises. For example, gymnasts are extremely strong at great ranges of motion through the practice of isometric holds.

[edit] 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 has concluded that isometrics may not be the best way for astronauts to maintain muscle tissue.^[9]

[edit] See also

• Dynamic tension

[edit] References

[edit] External links

• Public domain pamphlets on isometric exercises
• [http://www.isometric-exercises.com/index.html Isometric exercises

tutorial]

• [http://www.sandowplus.co.uk/Competition/Zass/zassintro.htm

v • d • e Musculoskeletal physiology Muscular Hand strength · Muscle tone Exertion (Exercise) · Movement (Eye movement, Gait, Locomotion) Muscle contraction (Isometric, Isotonic, Contraction) Skeletal (Bone/cartilage) Bone density · Bone remodeling (Osseointegration, Bone resorption, Osteolysis) Osteogenesis · Chondrogenesis