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Isometric Training

Monday, September 15th, 2008 | General | 807 Times Read

Isometric exercises, also known as static strength training, involve muscular actions in which the length of the muscle does not change and there is no visible movement at the joint (1).

In order to improve limit strength or explosiveness, isometric training in its various forms should never be applied isolatedly. However, it’s extremely effective in combination with concentric, eccentric and plyometric exercises. There are various subcategories of the isometric method. Basically, we distinguish between exercises with load and ones only done with bodyweight.

Isometric Training without Load:

Here one holds the body in a certain position and isometrically contracts the corresponding muscles.
Some examples which convey the diversity of isometric training:
* Descend into a squat and hold the position until failure.
* Slowly descend into a half squat, hold the position for 10 seconds, slowly descend into a parallel squat, hold for 10 seconds, slowly descend into a full squat, hold for 10 seconds and rise up. This is one repetition, repeat as many times as you like.
* Descend into a half squat, hold the position for 3 seconds and then jump up.

Isometric Training with Load:

Regarding the kind of loading, Cometti (2) distinguishes bewtween three methods: overcoming isometrics, yielding isometrics and the stato-dynamic method.

Overcoming Isometrics

The joint and muscle are worked against an immovable force (eg squat rack, wall) for four to six seconds with maximum counterpressure. This method makes sense only when it’s really done with maximum counterpressure. This method should be applied wisely as it’s very stressfull both physically and mentally.
Goal: increase limit strength

Yielding Isometrics

In this method low to high loads are held in a certain joint-angle (eg half squat) until failure. The high degree of muscle activation which occurs in yielding isometrics leads to strong hypertrophy stimuli. The graph below shows that the electric activity (this means more fiber recrutement) of the muscle rises with increasing fatigue.

Accordingly, this method of isometrics is well suited to induce maximum muscle activity using the effect of fatigue. This means that high loads aren’t needed which is a big advantage of yielding isometric exercises. The disadvantage lies in the unspecific execution (training of intermuscular coordination of sportspecific movements is neglected).

Stato-Dynamic Method

This manifold method can be combined with eccentric and - more common - concentric training. Regarding the latter, here one descends into a certain position, stops, holds it isometrically for two to three seconds and then continues the exercise explosively. The stop is often done in a position which is important for athletic performance (eg half squat) or in the so-called sticky points.

Example: Stato-Dynamic Half Squat (performed with 60-70% of 1RM, six sets at six reps)

On the one hand increasing time under tension using isometric stops leads to higher hypetrophy stimuli. On the other hand the tension created by the isometric hold innervates a relatively high number of neuro-motoric units. After the stop, the innervated musclefibers enable faster and stronger contraction of the muscle (3). Therefore the stato-dynamic method is extremely helpful in the training of speed strength.

Advantages of Isometric Training:

- Easy realization. Beginners don’t even need weights as isometric exercises without load suffice in early stages of preparation.
- Strength improves very fast.
- It enables speficic concentration on the muscle in the desired joint angle.- Isometric training improves explosiveness and speed of a movement if one performs the isometric hold in the starting position of the movement. For example the isometric half squat would be a choice for athletes who want to improve the vertical jump.
- Because isometrics only recruit fast twitch fibers they are of greatest use in the training of speed dominant sports (4).
- Isometric training can be beneficial in the training of bodybuilders. Due to maximum tension it helps gaining mass quickly and induces less soreness than eccentric training for example (5).
- It is well suited for rehabilitation training. During the immobilization after injuries muscles can lose up to 75% of their former strength due to the degradation of fast twitch fibers (6). Isometric training which concentrates on the fast twitch fibers can stop this loss of strength, that is if the injury allows it. Nonetheless dynamic movements are required too in the rehabilitation process since the immobilization leads to a decrease in the amount of sarkomers which isometric training can’t increase (7).

Disadvantages:

- Isometric training neglects intermuscular coordination. Thus it should only be used supplementary in combination with other methods of strength training.
- Gains from isometric holds in a certain joint angle doen’t transfer over to other joint angles (9).
- The maximum tension which is created during isometric holds exerts negative influence on flexibilty (8).
- Trainees adapt relatively quickly to isometric training and strength gains stagnate. Elite level athletes reach their peak after 6 to 8 weeks (9).
- Strong athletes must use extreme loads in order to achieve a training stiumli.
- Despite their great ability to increase muscle mass, isometrics don’t lead to a capillarisation of the muscle. Therefore, they’re not beneficial for the cardiovascular system (10).

References:
1) Fleck, S.J. and Kraemer, W. Designing Resistance Training Programs 3rd Edition. Campaign, IL: Human Kinetics (2004)
2) Cometti, G.: Les methodes moderne de musculation. Tome I: Données théoriques. Univ. de. Bourgogne, Dijon 1988
3) Dobrolowskij, D., E. Golowin: Eine Methode zur Ausbildung der Explosivkraft. Die Lehre der Leichtathletik (1974)
4) Eriksson, E.: Rehabilitation of muscle function after sport injury - Major problems in sports medicine. Int. J. Sports Medicine 2 (1981)
5) Talag T.T.: Residual muscular soreness influenced by concentric, eccentric and static contractions. Res. Quart. 44 (1973)
6) Scharf, H.P. et al: Das Atrophiemuster der Oberschenkelmuskulatur nach Sportverletzungen und seine Konsequenzen für die Rehabilitation. Dt. Z. Sportmed. 43 (1992)
7) Goldspink, G.: Malleability of the motor system: a comparative approach. J. exp. Biol. 115 (1985)
8 ) Marhold, G.: Biomechanische Merkmale der Entwicklung sportlicher Techniken. Theorie und Praxis der Körperkultur (1987)
9) Zatsiorsky, V.M., Kraemer, W.: Science and Practice of Strength Training (2nd edition). Champaign, IL: Human Kinetics (2006)
10) Weineck, J.: Optimales Training. Spitta Verlag, Erlangen (2004)

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