There are 3 different causes for Muscle breakdown. On the one hand, the "normal" loss in the context of the aging process comes into question. On the other hand, the decrease in muscle mass can be the result of inactivity or a disease of the muscles or the nervous system.
Muscle loss means that a muscle becomes measurably and sometimes visibly thinner and loses its strength.
Muscle loss means that a muscle becomes measurably and sometimes visibly thinner and loses its strength. The muscle can be roughly divided into two main structures. On the one hand, there are the structures that can actively contract (contract) and, on the other hand, the passive tissue, which includes the tendons and the sheaths of the entire muscle and its subunits. Muscle breakdown primarily takes place in the contractile elements. The predominant process is a decrease in the cross section of the muscle fibers, in the second place, a decrease in their number.
Two mechanisms must be intact for a muscle to function properly. On the one hand, this is the function of the nervous system, where impulses are generated and directed to the muscle. On the other hand, it is the proper functioning of the muscle itself. He must be able to receive and process the incoming stimuli and he must be able to contract.
The stimulus absorption takes place in the so-called motor end plates. From there, the incoming impulse is passed on to the inside of the muscle via certain channel systems, where it leads to calcium being released into the cell interior. If the concentration is high enough, the sarcomeres, the smallest functional units in the muscle cell, undergo a contraction with energy consumption, during which the sarcomeres are shortened or put into increased tension.
In addition to producing heat, the primary task of a muscle is to develop strength through contractions. The stronger the stimulus signal that reaches the muscle via the nerves, the more sarcomeres are tensed in the millions of muscle fibers and the greater the strength development in the overall muscle. Frequent and intensive use of the muscle can lead to an increase in strength due to an increase in the cross-section of the muscle fibers.
The resulting force is transferred to the attachments on the bone via the tendons. The pull either creates a movement in the joints involved or increases tension. In the first case the muscles do dynamic work, in the second static work. The activity is directed by the target programs in the brain. This creates finely tuned motor patterns in which the acting muscles appear either as opponents or as teamworkers.
When an impulse from the brain initiates movement in a particular joint, all the muscles that are necessary for this are automatically activated. The opponents (antagonists) are inhibited. This mechanism is important for optimal movement of the movement function.
If the antagonists were also tensing, this would hinder movement. Smooth coordinated movements would then not be possible.
Static muscle work is always required when it comes to stabilizing certain joints or body regions. Well-known examples of this are the stabilization of the trunk and the spine during dynamic activities of the extremities or knee stabilization while standing. It is particularly important that agonists and antagonists work together when the knees are slightly bent. The main active controlling muscles in this case are the knee extensors. They control the stance and prevent the legs from collapsing. At the same time, however, the knee flexors are required to keep the position of the two joint partners in relation to one another in the optimal range. This prevents excessive stress on the articular cartilage and menisci.
The condition of a muscle depends on whether it is being used or not. If external or internal factors mean that it is not used or only rarely used, muscle loss occurs.
The "normal" process of muscle breakdown begins at the age of 25 if the person does not actively take countermeasures. Less active women and men lose an average of 5 to 10 percent of their muscle mass every decade of life. The process accelerates again significantly when around the age of sixty is passed. The result is an overall reduced performance, which is noticeable, for example, when climbing stairs or when a sporting activity is carried out. Regular exercise can significantly slow down the breakdown process. It also makes sense to start at an older age.
Muscles break down very quickly if they stop working for a while or permanently. A so-called Inactivity atrophy out. The muscle becomes measurably and visibly thinner and loses strength and function; performance decreases. Typical causes for this process are the immobilization of a part of the body after injuries or the inactivity of the entire skeletal musculature due to bed rest due to illness or old age. If the causes of the atrophy are eliminated, the affected muscles can be rebuilt through training. However, the construction is laborious and takes significantly longer than the dismantling.
In bedridden people, not only the skeletal muscles break down, but also the respiratory muscles and the muscles of the internal organs. In addition to the motor skills, this also affects the functions of the affected organs.
Certain illnesses and injuries can cause the muscle to stop working and break down. A typical consequence of injury is paraplegia caused by a severing of the spinal cord. Individual peripheral nerves can also be injured and paralysis of the muscles supplied.
Genetically determined diseases, known as muscular dystrophy, damage the muscles themselves or their conduction system. This leads to muscle loss and an increasing reduction in performance, sometimes with premature death.