Isometric exercise

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.

Overcoming versus yielding

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).

An example of this in the context of the bench press would be that a yielding isometric would be holding the bar at a given place even though it could be pressed higher, and an overcoming 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, one can be exerting more force and simply unable to move it. The yielding wavers slightly into concentric/eccentric actions due to inexact control, whereas the overcoming is more purely isometric and can involve more variation in the force used since one can press harder without the bar moving.

Definition

Isometric exerciGBse

Isometric resistance

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

• The body's own structure and ground
• Structural items (e.g., pushing against a fence)
• Free weights, weights 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, with examples from the static holds in certain branches of yoga or oriental martial arts, for example kung fu.

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. Isometrics fell out of favor as it was discovered that many of the principal advocates were using anabolic steroids to enhance their gains.

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.

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 as compared to the quieter murmur of aortic stenosis. They can also be used to prevent Disuse Syndrome in a limb that has been immobilized by a cast, following a fracture.

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.

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.

See also

• Dynamic tension

External links

• Isometric exercises tutorial
• Alexander Zass