By the healthiergang writer , personal trainer.
Isometric Exercises: Muscles
Before going into the specifics, it is good to clarify some concepts relating to the characteristics of the muscles.
Skeletal muscles are the active organs of the locomotor system thanks to which voluntary movement is possible. In a muscle of this type there is a fleshy red part, the belly and a white defined tendon that inserts itself on the bone.
The belly is inserted on the bony surface through two distinct tendon heads in:
- head of origin or proximal insertion, the termination of the muscle closest to the skeleton and consequently less mobile.
- head of insertion or distal insertion or the terminal point furthest from the skeleton and therefore more mobile.
1. Isometric contraction
Skeletal muscle tissue is made up of fibers that have the ability to voluntarily shorten through a mechanism called contraction; if this happens, a force develops which, transmitted to the bones through the tendons, in the presence of a joint, allows movement.
There are mainly 2 types of contraction (in skeletal muscles) depending on whether the length of the muscle varies or not during this process.
If the length of the muscle belly undergoes variations, we speak of isotonic (dynamic) contraction. This can in turn be divided into concentric, in the case in which there is, as a result of the contraction, a shortening of the muscle and eccentric if the force develops as resistance to an elongation caused by an external force.
The other type of contraction is isometric, in this case the muscle does not shorten (static) and therefore muscle tension develops at a constant length.
But when does an isometric contraction take place?
If we try to lift a load that is too heavy for us, that is, if we are not able to generate enough muscle tension to move the load, the muscle is not able to shorten while maintaining a very high tension, we speak in this case of contraction. maximum isometric or maximal isometry.
When instead we are in the middle of a dynamic contraction (see concentric isotonic contraction) and we insert an isometric action through, for example a pause in the middle of the movement, we are in the presence of a total isometric contraction or total isometry.
By isometric training we mean that type of training that exclusively involves the use of isometric contractions.
This methodology is particularly effective in the development of strength even, according to some studies, more than dynamic contractions. This is possible thanks to a progressive recruitment of the deeper fibers, due to the fatigue of those activated, primarily due to contraction.
In isometries, the intensity of contraction must always be taken into consideration; in fact, to obtain a training effect it is necessary that the force used in the contraction exceeds a threshold value usually detected around 30% of the maximum force that can be developed by that muscle district (The best training effect is achieved with stimulations between 40% and 50%) .
2. Initial Considerations
Before going into isometric training head down, some points should be taken into consideration:
1. Muscle use at each contraction must be between 50% and 100% and inversely proportional to its duration which varies from 12 '' to 50% up to 2 '' to 100%.
2. Train the target muscle in different angles.
3. If we do not have to train a specific muscle but a competition gesture, it is good to break it down and understand at what point of the movement we are lacking, for example: if we have a deficiency in the sticking point of the squat insert in our routine some series with a point of isometry in that phase can help us to improve the ascent from the squat.
4. The repetitions must be from 1 to 6 for each training session.
5 The recovery between repetitions must be between 30 '' and 3 minutes depending on the intensity of the contraction, during this time, it is possible to train other muscle groups also with the same method.
6. The total duration of the workout should not exceed 10 minutes.
7. The training session must always be concluded with a stretching session.
3. Advantages and Disadvantages
Now let's move on to the pros and cons of this technique:
Increase in muscle strength given by the greater recruitment of fibers;
- Increase of resistance, given its purely anaerobic nature;
- Strength development in critical positions of some sporting gestures;
- Allows you to measure the load in all positions of the body segments;
- It presents a wide range of exercises and their variations;
- Used in rehabilitation;
- It does not require special equipment and consequently it can be carried out practically anywhere;
- Given the duration it is also suitable for those who have little time available;
- Inserted before the execution of a series with dynamic contractions, it can accelerate the process of muscle fatigue, therefore it is indicated as a pre-fatigue exercise, especially to stimulate the isolation of deficient muscle groups;
- It is possible to exploit its peculiarities at the end of the series to lead to muscle failure.
- The increase in strength occurs mainly in the chosen position, it is therefore recommended to act on at least three different angles for each muscle;
- It can adversely affect motor coordination;
- It can cause a reduction in the elasticity of the fibers as well as in their ability to relax;
- It quickly strains the central nervous system (the duration of the session should not be too long);
- It is not suitable for those sports that require speed and rapid strength because it slows down the responsiveness of the body's kinetic chains. In these cases it is advisable to use isometric training only for short cycles for the development of maximum strength and in positions characteristic of the sport in question;
- Although isometric exercises do not require particular physical skills, they involve the back muscles which must be protected from excessive efforts in “unconventional” positions;
- Isometric training causes a momentary increase in blood pressure, due to the crushing of blood vessels in turn caused by the high intensity of the contraction. It is therefore contraindicated for elderly, cardiopathic and very young subjects.
Regarding this last point, various studies have shown that, in healthy subjects, performing 3 workouts per week for 8 weeks, there is a decrease in resting systolic and diastolic blood pressure compared to a control group that did not perform any type of work out.
This improvement seems to be linked to the stimulation of vasodilating agents such as nitric oxide, stimulated by the momentary reduction in blood flow due to the crushing of the vessels.
In conclusion, it can be added that this training methodology can be useful both to powerlifters and bodybuiders, with deficiencies in the execution of some technical gestures or muscle groups, and to individuals with a busy life, therefore unable to train in the classic way.