Different Types of Isometrics

[Guest guest]

Those of you who have read my " Supertraining " book may have noticed that I do

not regard isometric training simply as one discrete form of training.

Instead, I divide it into two different classes: slow isometrics and

explosive isometrics, as discussed in Ch 4:

ISOMETRIC TRAINING

Siff M C Supertraining Ch 4.2.4

< ..... isometric training is not simply a matter of holding a static muscle

contraction for a given time. Isometric contraction requires a muscle to

increase its tension from rest to a maximum or sub-maximal value over a

certain time (rise or ‘attack’ time), to sustain this tension for another

period (the resistance phase) and to decrease this tension to rest or a lower

value (decay time). Consequently, one may distinguish between explosive

isometrics, which have a very brief rise time, and slow isometrics, with a

much longer rise time (Fig 4.12). The isometric contraction may be produced

by voluntary contraction or involuntarily by the reflex response of the

muscle between the eccentric and concentric phases of plyometric activities

such as the depth jump or weightlifting clean-and-jerk. The different types

of isometric contraction are categorised in Figure 4.11.

Each class of isometric training produces its own distinct training effects.

If isometric exercises are executed with the accent on the speed of

developing force, then they can be as effective for developing explosive

strength as dynamic exercises. The steepness of the force-time curve (Fig

3.3) and the greater magnitude of maximum isometric than dynamic maximum

force for equivalent joint angles is the basis for this assertion.

Therefore, it is doubtful whether it is always productive to maintain a rigid

distinction between dynamic and isometric exercise. In general, the harder

the muscles work in overcoming large resistance, the more closely the work

becomes isometric, as may be seen from the force-velocity curves of muscle

action (Figs 3.15 & 3.16). In other words, isometric work is really the

limiting case of dynamic work as the velocity of movement tends to zero.....

Furthermore, because the inhibitory effects usually associated with voluntary

muscle action are not encountered in reflexive isometric contraction, even

greater explosive force can be displayed isometrically than dynamically.

In connection with this, it makes sense to distinguish isometric training for

developing absolute strength and isometric training for developing explosive

strength and to use one or the other in the appropriate circumstances.

However, this still requires detailed experimental corroboration.

Nevertheless, isometrics should not be neglected as a means of strength

development, so that negative evaluations of this method are premature......>

The following research article provides further information on this topic.

For anyone who may subscribe to the methods of SuperSlow training, these

findings should be especially interesting, because they show distinct

differences in the training effects and adaptation using types of slow vs

ballistic training, even under isometric conditions.

Med Sci Sports Exerc 2001 Jul;33(7):1220-7

Progressive versus rapid rate of contraction during 7 wk of isometric

resistance training.

Maffiuletti NA, A.

PURPOSE: The aim of this study was to compare the effects of isometric

training performed with progressive versus rapid rate of contraction on the

knee extensor neuromuscular properties over a 7-week period.

METHODS: Sixteen healthy male subjects trained quadriceps femoris muscle in a

leg extension machine three times a week during 7 wk. The training sessions

consisted of six sets of six maximal isometric contractions. A first group

trained by performing progressive contractions lasting 4 secs, whereas a

second group performed contractions with a rapid rate of contraction (i.e.,

ballistic contractions) lasting about 1 sec.

RESULTS: Both groups significantly increased the isometric and isokinetic

voluntary torque, and the respective absolute or relative gains were

comparable. Isometric training performed with progressive rate of contraction

affected the evoked action potential (M wave) of the vastus lateralis muscle

and not the related twitch properties. On the other hand, the isometric

training completed with ballistic contractions significantly modified the

twitch contractile properties of the knee extensors and not the associated M

waves of both vastus medialis and vastus lateralis.

CONCLUSION: Knee extensors adapted specifically their neuromuscular

properties to the type of rate of contraction performed during 7-wk isometric

resistance training. Progressive isometric contractions produced

modifications of the nervous system at peripheral level (i.e., muscle

membrane electrical activity), whereas ballistic isometric contractions

affected the knee extensor contractile muscle properties (i.e.,

excitation-contraction coupling).

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Dr Mel C Siff

Denver, USA

http://groups.yahoo.com/group/Supertraining/