Static muscle work
The static muscle work is ideally isometric, i.e. the length of the muscle remains constant. The attachment of the muscle is as far away from the joint (pivot point) as possible (see Fig. 1). Working with a long lever arm means little effort, comparable to a crowbar, with which even heavy loads can be lifted easily, but the lever travel is only small.
In the fibers of statically working muscles such as the brachioradialis (see Fig. 2), there is a lot of myoglobin (= red muscle dye) for O2 storage. In static muscle work, the blood vessels in the muscle are permanently compressed by their own muscle mass. This results in reduced blood circulation and a lack of oxygen, which can partly be corrected by oxygen from the myoglobin. The tension of the brachioradial m. as an example of static muscle work.
With very long static work the lack of oxygen leads to anaerobic energy production. Lactate accumulates in the muscle and this over acidified. A further lack of energy causes a metabolic disorder in the muscle cell. This leads to an attempt at repair within the muscle and protein is deposited. These deposits are myogeloses (scars in the muscle).
Dynamic muscle work
Dynamic muscle work mainly affects our entire musculoskeletal system. Ideally, it is isotonic, i.e. the tension of the muscle remains constant as its length changes. Since changing conditions always cause slight fluctuations in the tension of the muscles, dynamic muscle work is in reality auxotonic.
The approach of the muscle should be as close as possible to the joint (see Fig. 3) so that a small contraction distance results in the largest possible movement excursion. Muscle fibers of dynamically working musculature contain little myoglobin because a short tension phase is followed directly by a relaxation phase, in which the oxygen debt is released again.
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