Isometric exercise

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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 or are held in a static position while opposed by resistance.

1 Definition
2 History
3 Isometrics today
4 Disadvantages of isometric exercises
5 Isometrics and NASA
6 Sample isometric exercises
7 References
8 External links
- 8.1 Public domain books on isometric exercises

[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 in which the contraction strength does not change but the joint angle does. Resistance to isometric contractions can involve maximal contractions of the muscle against the body's own muscle (i.e. pressing the palms together in front of the body) or structural items (e.g. pushing against a door frame), but can also involve holding a joint position against a sub-maximal contraction (e.g. holding a resistance band in a fixed position).

[edit] History

Isometrics was first brought to the public’s attention in the early days of physical culture, the precursor to bodybuilding. Many of the great bodybuilders of the day used and incorporated Isometrics into their training regimes. Perhaps the most famous of the Isometric advocates was Charles Atlas. In his course he advocated a series of dynamic tension exercises which included Isometrics.^[2] Unfortunately, isometrics fell out of favor as it was discovered that many of the principal advocates were using steroids to enhance their gains.^[3] Charles Atlas' methods of self-resistance did not have traditional resistance limits as weight exercises do, as the tissue exercising against can provide greater resistance as it develops in tandem. His system was flawed in that there was no method of measuring progression; users were not motivated by measurable progress as assessment of increases in strength subjective and lacked an empirical means of demonstrating progress.

The Bullworker is an isometric exercise device consisting of a spring compressible by handles or straps. It has been available in several successive versions for around 45 years.

[edit] Isometrics today

Isometric approaches to exercise have seen a sudden resurgence of late due to the work of John Little and Pete Sisco, who popularized it in a system called Static Contraction Training. This involved using isometrics with measurable progression by using very heavy weights held near lockout in whatever position allows the heaviest weight, moved only about an inch to get there, and held for a length of time. This bypasses the previous limitations of isometric exercise which limited guaranteed progression due to dependance on intuition and feel for evaluating the stresses being placed on the muscles. Now, some isometric machines have been developed which provide digital readouts of the stress being placed on a bar, rather than using plateloading. This saves time, allows more gradual progression, better isolates the isometric approach as there is absolutely no movement, and also allows for lighter loads on weaker days.

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. Other systems dedicate themselves entirely to isometrics; among them are the aforementioned Static Contraction Training, and the Max Contraction Training developed later by John Little. MCT uses the same isometric high-weight principles, but differs in that it utilizes isolation exercises that avoid bearing load with one's bone structure, resulting in different movements for targetting the pressing musculature.

To date the success of these systems have received successful business, and the authors publish testimonials with claims of up to 20-30 pounds of muscle being generated from the heavier loads the lack of movement and prime bone alignment allow to be safely loaded. As intensity increases, maximum time under tension decreases, so it also takes less time for these exercises.

Isometric exercises can also be used at the bedside to differentiate various heart murmurs; the murmur of mitral regurgitation gets worse (louder)^[4] as compared to the murmur of aortic stenosis (softer).^[5]

[edit] Disadvantages of isometric exercises

Isometric exercises have some disadvantages as compared to isotonic movements. Some exercises can be more difficult or more dangerous to perform due to the weight involved (i.e. an isometric squat). In addition, isometric training will only increase strength at the specific joint angles of the exercises performed, while isotonic exercise increases strength throughout the full range of motion. In order to isometrically train the full range of motion, exercises must be repeated at a variety of joint angles. This is due to the neurological effects of isometric exercises on force output at specific joint angles.^[6]

[edit] Isometrics and NASA

NASA has researched the use of isometrics in preventing muscle atrophy experienced by astronauts as a result of living in a zero gravity environment. Kenneth Baldwin^[7], a professor in the Physiology and Biophysics Department at the University of California, Irvine, conducted studies in order to better understand how muscles work. 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. Due to the fact that 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.^[8]

[edit] Sample isometric exercises

Isometric exercises can be done using the body's own weight, weight training equipment, resistance bands or everyday objects such as doorframes and towels.

Below are examples of both, one without equipment and the other with the use of the a gym Smith machine.

Isometric abdominal tension

Stand or sit tall and straight
Breathe in and pull in the stomach
Maximally contract the abdominal muscles (rib cage will dip down slightly and pelvis may rotate upwards)
Breathe out making an “sssss” for seven seconds (this will cause intra-abdominal contraction)
Keep the stomach in tight and inhale
Repeat ten times; do not relax the stomach until completely finished all ten repetitions

Isometric Biceps Curl Warm up biceps with light biceps curls.

Stand in a Smith machine.
Place empty bar at about shoulder height (adjust for maximum effect)
Bring hands up to the bar, mimicking the top of a biceps curl
Adjust bar to be slightly lower than this height; the elbow should be close to maximum flexion
Keep the back straight and abdominal muscles tense.
Load the bar with very heavy weight to allow for maximum contraction force
Attempt to raise the bar approximately one inch, do not move the elbows to be directly beneath the bar
Hold for seven seconds; if the movement can be held for longer than seven seconds, the muscle is not at maximum contraction
After seven seconds, safely lower the bar