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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 1.1 Resistance in isometric exercises 2 History 3 Isometrics today 4 Isometric exercises in comparison with dynamic exercises 5 Isometrics and NASA 6 Sample isometric exercises 7 References 8 See also 9 External links 9.1 Public domain books on isometric exercises

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 in isometric exercises typically involve maximal 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 or weights machines

• pressure plate type equipment that have a digital readout of maximal force.

Isometrics can also involve holding a joint in position against a sub-maximal contraction (e.g., holding a resistance band in a fixed position).

Isometrics are thousands of years old and examples can be found in the static holds in certain branches of yoga or Chinese martial arts.

Isometrics was 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 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] He had learned these exercises from the "Conscious Evolution" Course of Alois P. Swoboda. Atlas said "everything he knew he learned from A.P. Swoboda".^[3] Unfortunately, isometrics fell out of favor as it was discovered that many of the principal advocates were using steroids to enhance their gains.^[4] 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.

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 dependence 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 targeting 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)^[5] as compared to the murmur of aortic stenosis (softer).^[6]

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.^{[citation needed]} 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. Interestingly, a study has shown that while dynamic exercises are 5% better at enhancing the twitch force of a muscle than isometric exercises, isometrics are 32% better than dynamic exercises at increasing maximal muscle power.^[7]

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^[8], 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. 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]

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 a Smith machine.

Isometric abdominal tension

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

Isometric Biceps Curl Warm up biceps with light biceps curls.

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

Perform the exercise once, and allow a full week to pass before repeating to avoid damaging the muscle.

1. ^ Article on static strength training
2. ^ Charles Atlas and Isometric exercise
3. ^ Alois P. Swoboda on Sandow Plus
4. ^ Isometrics and steroid use
5. ^ Evaluation of Cardiac Murmurs in the Clinic Setting
6. ^ The effect of isometric exercise on the systolic murmur of patients with idiopathic hypertrophic subaortic stenosis
7. ^ Duchateau J, Hainaut K (1984). "Isometric or dynamic training: differential effects on mechanical properties of a human muscle". Journal of applied physiology: respiratory, environmental and exercise physiology 56 (2): 296–301. PMID 6706740. 
8. ^ Kenneth Baldwin at University of California
9. ^ NASA article on muscular hypertrophy and atrophy

• Dynamic Strength
• Dynamic Tension

• Compilation of public domain pamphlets on isometric exercises
  • Atlas was Right All Along
  • Wittenburg Isometrics
  • Tegner's Isometric Power Exercises