In exercise science, 3 forms of muscle work are described. Concentric contraction is one of them. It plays an important role in the dynamics of the body.
What is concentric crane contraction?
Concentric contraction is defined as dynamic muscle work in which there is a change in the length of the muscle. Concentric contraction is defined as dynamic muscle work in which there is a change in the length of the muscle. Tendon origin and attachment approach each other. This process is visible in the resulting movement and muscle belly. The process originates in the smallest functional units, the muscle fibers. These elements, also known as sarcomeres, have an active complex of two protein molecules, actin and myosin. In the interaction of these two filaments, the shortening process takes place in the sarcomeres under energy consumption, which adds up and is transmitted to the muscle as a whole. The extent of shortening is limited by the fact that two adjacent actin filaments abut at a given point in time, causing all contact sites between actin and myosin to be occupied and inactive. The magnitude of force development is also subject to this mechanism. It is the reason why each muscle reaches its maximum force in the middle movement path and becomes increasingly insufficient in the inner movement path. When flexing at the elbow, the biceps reaches its highest level of strength at 90° of flexion. If the forearm is subsequently moved further toward the upper arm, the efficiency decreases more and more.
Function and task
During concentric contraction, force is developed and converted into movement. The motor system is usually organized so that the fixed point is located at one of the involved bones of the joint. In this way, the location of the fixed point allows the free-moving bone to be pulled toward it by the concentric muscle work. Concentric contractions play the decisive role in many activities of daily life. They cause all movements in normal everyday life, in professional activities and in sports that serve active free movement and locomotion. A typical everyday activity is bringing the arm and hand to the mouth to eat or drink. When walking, the swing leg phase is characterized by concentric contractions. Hip and knee joints are flexed. Ankle and toe joints are extended to set the leg forward or backward. Countless athletic movements are characterized by concentric muscle activity. Any movement with at least one free end of movement that has a path gain as its goal is a concentric movement. This includes the kicking movements in soccer as well as the hitting and throwing movements in handball, volleyball or athletic throwing disciplines. Gymnasts use a complete free kinematic chain for the somersault. The impulse for the movement is provided by concentric contractions of various muscle chains in the legs, arms and trunk. A completely different, but nevertheless important, function of muscles is the generation of heat. In all types of muscular work, heat is generated in addition to force. By far the most during concentric contractions. This is because there are the best conditions for increased metabolism, which is the basic requirement for heat production. The heat produced is used in the muscle itself, but is also released to the surrounding body regions and organs. On the one hand, it is used there to maintain the core body temperature and the thermal environment, which are the optimal conditions for metabolic activities in the tissues, organs and cells.
Diseases and ailments
Certain injuries or diseases affecting the muscle itself or the systems that generate or conduct the necessary nerve impulses to the muscle can lead to muscle breakdown and consequent loss of function. The extent of subsequent damage depends on the nature of the disease and the size of the defects. Spinal cord injuries or lesions of individual nerves result in acute and often permanent loss of muscle function. Complete severance of the spinal cord results in paraplegia, in which all muscles fail whose supply area lies below the lesion. The higher the damage to the spinal cord, the more muscles and body areas are affected.In this context, one speaks of a high or deep cross-section. Damage to individual nerves leads to a failure of the muscles that receive their impulses from there. Such injuries often occur after external force and pressure (stab wounds, plaster casts) or, less frequently, during surgical interventions. The result is a flaccid paralysis with loss of function. The severed neural structures may be able to be surgically reconnected if the damaging event did not occur too long ago. A group of diseases that lead to muscle degeneration based on genetic defects are the so-called muscular dystrophies. They differ in terms of the speed of progression and the primary regions affected. What they all have in common, however, is the gradual progression to complete loss of muscle function. Although the eccentric contractions are initially more intensely affected, the concentric ones are also affected early on, especially with weight bearing and movements against gravity. Amyotrophic lateral sclerosis takes a similar, often very fulminant course. It is a degenerative disease, the cause of which has not yet been conclusively clarified. All muscles of the human body are progressively affected. Affection of the respiratory muscles usually leads to death. Basically, in typical sports injuries such as strains, muscle fiber tears and muscle ruptures, the eccentric contractions are affected first. Concentric muscle work, with the metabolic aspect described above, is affected only when the muscles are inactive for a long period of time. Except for injuries with immobilization, this is typical in the elderly who are permanently or prolongedly bedridden.
