There are 3 different causes of muscle loss. On the one hand, the “normal” loss as part of the aging process comes into question. Second, the decrease in muscle mass may be a result of inactivity or disease of the muscle or nervous system.
What is muscle wasting?
Muscle wasting means that a muscle measurably and sometimes visibly thins and loses strength. Muscle breakdown means that a muscle measurably and sometimes visibly thins and loses strength. Very roughly, muscle can be divided into two main structures. These are, first, the structures that can actively contract (contract) and, second, the passive tissue, which includes the tendons and sheaths of the overall muscle and its subunits. Primarily, muscle breakdown takes place in the contractile elements. The predominant process is a decrease in the cross-section of muscle fibers, and secondarily, a reduction in their number. Two mechanisms must be intact for a muscle to function without interference. One is the function of the nervous system, where impulses are generated and directed to the muscle. The other is the proper function of the muscle itself. It must be able to receive and process the incoming stimuli and it must be able to contract. Stimulus reception takes place in the so-called motor end plates. From there, the incoming impulse is transmitted via certain channel systems to the interior of the muscle, where it leads to a calcium release into the interior of the cell. If the concentration is high enough, a contraction occurs in the sarcomeres, the smallest functional units in the muscle cell, under energy consumption, in which the sarcomeres are shortened or put into increased tension.
Function and task
The primary task of a muscle, in addition to heat production, is to develop force through contraction. The stronger the stimulus signal that reaches the muscle via the nerves, the more sarcomeres in the millions of muscle fibers are contracted and the greater the force development in the overall muscle. Frequent and intensive use of the muscle can result in an increase in force due to an increase in the cross-section of the muscle fibers. The resulting force is transmitted through the tendons to the attachments on the bone. The pull there either causes movement in the joints involved or results in increased tension. In the first case, the muscles perform dynamic work, in the second static work. The activity is controlled by the target programs in the brain. This results in finely tuned motor patterns in which the acting muscles act either as opponents or as teamworkers. When an impulse from the brain initiates a movement in a particular joint, all the muscles required for this are automatically activated. The opponents (antagonists) are inhibited. This mechanism is important for optimal movement function. If the antagonists were also to tense up, this would impede the movement. Flowing coordinated movements would then not be possible. Static muscle work is always required when it is necessary to stabilize certain joints or body regions. Well-known examples of this are the stabilization of the trunk and spine during dynamic activities of the extremities or knee stabilization while standing. Especially when the knees are slightly bent, it is important that agonists and antagonists work together. The main active controlling muscles in that case are the knee extensors. They control the stance and prevent the legs from collapsing. At the same time, however, the knee flexors are called upon to maintain the position of the two joint partners in relation to each other in the optimal range. This prevents excessive stress on the joint cartilage and menisci.
Diseases and complaints
The condition of a muscle depends on whether it is used or not. If external or internal factors cause it to be used little or not at all, muscle breakdown occurs. The “normal” degradation process of the musculature starts at the age of 25 if the person does not actively counteract it. In less active women and men, an average of 5 – 10 percent of muscle mass is lost every decade of life. The process accelerates even more when the age of sixty is exceeded. The result is an overall reduction in performance, which becomes noticeable when climbing stairs, for example, or when a sporting activity is carried out.Regular physical activity can significantly slow down the degradation process. It also makes sense to start at an older age. Muscles break down very quickly if they are not used for a while or permanently. A so-called inactivity atrophy develops. The muscle becomes measurably and visibly thinner and loses strength and function; performance decreases. Typical causes of this process are immobilization of a body part after injury or inactivity of the entire skeletal musculature due to bed confinement as a result of disease or old age. If the causes of atrophy are eliminated, the affected muscles can be rebuilt through exercise. However, the build-up is laborious and takes much longer than the breakdown. In bedridden people, not only the skeletal muscles but also the respiratory muscles and the muscles of the internal organs break down. As a result, the functions of the affected organs are impaired in addition to motor function. Certain diseases and injuries can cause the muscle to stop working and break down. A typical injury consequence is paraplegia due to a spinal cord transection. Individual peripheral nerves can also be injured, resulting in paralysis of the supplied muscles. Genetically determined diseases known as muscular dystrophy damage the muscles themselves or their conduction system. As a result, there is muscle breakdown and an increasing reduction in performance, sometimes with premature death.
