The adjective concentric is used in the field of geometry to qualify for a figure that has the same center What other. The notion is also used with respect to two bodies.

We can understand the notion of concentric by observing the whites that are used to practice shooting. These elements are made up of several concentric circles of different sizes, the most important being the small circle that constitutes the center shared by all. Shooters with greater precision hit the center of the target. If the shot is not accurate, it can end up in any of the concentric circles that are part of the target.

Two geometric figures are not only considered concentric if they have the same center, but they can also share the origin or axis. In addition to circles, cylinders, tubes, spheres, and disks can fall into this category. The meridians of the Earth, for example, are concentric and all have the same radio, that is, not necessarily two figures must have different dimensions in order to be concentric.

The coaxial cables, for their part, present two concentric conductors. These cables that allow the transmission of high frequency electrical signals have a center conductor (known as nucleus) and another outside conductor (called braid or mesh). The core carries the information, while the braid acts as a ground and return reference. These concentric conductors are separated by the dielectric, which is responsible for insulating them. The entire set is also protected by another insulating cover.

Among muscle contractions, on the other hand, there are concentric heterometric contractions. In these contractions, a muscle manages to develop the tension it needs to overcome a resistance, shortening and displacing a sector of the body.

This type of contraction appears when a muscle insertion points are brought closer together. As it shortens, concentric contraction takes place. The persons who wish to develop their muscles, in this framework, they perform repetitions of concentric contractions and, their counterparts, eccentric contractions.

We speak of eccentric contractions to refer to the lengthening that any muscle presents when the endurance it faces is greater than the stress it exerts. In a case like this, its length increases during contraction. Every day when we finish a drink and lower our arms to rest the container on the table, for example, the biceps brachii experiences this type of contraction.

One of the everyday examples of this type of muscle contraction occurs when we bring a glass to our mouth to drink: as a consequence of this common action, the points insertion. Already in a field of controlled physical exercise, such as a gym, we can recognize examples that specifically look for this phenomenon:

* the extensions machine: The muscle called the quadriceps shortens during the action of lifting the weights, and this causes the advanced concentric contraction. In this case, the insertion points of said muscle;

* triceps with pulley: During triceps training, we lower and extend the arm, causing a concentric contraction in the muscle. The points of this muscle (the triceps brachii, which is located at the back of the arm) are also close in this case.

In the art world the term appears in the painting titled «Squares with concentric circles«, Published in 1913 by the Russian painter Vasili Kankinski, one of the forerunners of the abstraction in the world of painting. Scholars assure that his work began expressionism and the so-called lyrical abstraction, through a work that he titled «First abstract watercolor«.