From the Latin contractĭo, contraction is the action and effect of contracting or contracting. The term makes it possible to refer to the reduction to a smaller size, the acquisition of a custom, illness or vice, and the celebration of marriage.
Muscular, on the other hand, is what belongs to or relative to muscles. We can establish that muscular also has its etymological origin in Latin since the term is formed by three parts of that mentioned language: “mus”, which is synonymous with “mouse”; “Culus” which is equivalent to “small”; and finally the suffix “-ar”, which can be translated as “relative to”.
According to abbreviationfinder, muscles are organs made up of contractile fibers (known as muscle fibers) that can be linked to the skeleton (skeletal muscles) or form part of the structure of other organs or apparatus (visceral muscles).
A muscle contraction is a physiological process developed by the muscles when, depending on the tension, they are stretched or shortened. This process is controlled by the central nervous system and allows the production of motor power.
Thanks to this motor force, the upper muscles can move the contents of a cavity they cover (which smooth muscles do), move the body through the medium, or mobilize other objects (striated muscles).
In addition to all the above, it is important that we know that there are situations that generate modifications or alterations in what is muscle contraction. Specifically, among the most significant situations of this type are the following:
• Rigor mortis. This term is used to refer to the stiffness experienced by the muscles of a person who has died. Specifically, they will become absolutely rigid between three and four hours after the individual has died and will remain so for a whole day.
• Muscular atrophy. Failure to exercise the muscles, as happens for example to patients who spend a lot of time in bed, is the main reason for this situation, which basically consists in the fact that the muscle not only decreases in size but also in strength.
It is possible to distinguish between voluntary contractions (controlled by the brain) and involuntary reflexes (dependent on the spinal cord). Striated muscles contract voluntarily from a conscious effort originating in the brain. The brain signals are directed through the nerves to the motor neuron that stimulates the muscle fiber. Involuntary muscle contractions, on the other hand, originate in the spinal cord through a circuit with gray matter.
Another classification of muscle contractions allows us to refer to isotonic contractions (when muscle fibers contract and change their length), concentric contractions (the muscle shortens and mobilizes a part of the body to overcome resistance) and isometric contractions (the muscle remains static but generates tension), among others.
Specifically, we would have to establish that within isotonic contractions, of equal tension, there are two clearly differentiated types: the concentric ones, which we have already explained, and then there are the eccentric ones, which are defined by the fact that in them what the muscle is lengthening. This last situation occurs because the resistance is greater than the tension that is exerted by the muscle itself.