Composition | Muscle Fiber

Composition

In total, a muscle fiber consists of about three-quarters water, 20% protein (half of which is provided by the contractile proteins actin and myosin) and 5% ions, fats, glycogen (an energy store) and nitrogenous substances.

Types of muscle fibers

Two different types of muscle fibers are distinguished by their function. On the one hand there are the phasic, fast twitching muscle fibers (FT-fibers) and on the other hand the tonic, slow twitching muscle fibers (ST-fibers). The slowly twitching muscle fibers are also called red or type 1 fibers.

Their red color is due to the fact that they have a high concentration of myoglobin, which is an oxygen reservoir. Due to the high oxygen content, these fibers can apply a limited amount of force over a long period of time. They tire very slowly, but are not capable of high performance.

Such muscle fiber cells are found in the diaphragm or the eye muscles, among other places, i.e. muscles that are relatively permanently active but do not normally have to perform at high levels. The fast-twitching muscle fibers (type 2 or white fibers), on the other hand, contain less myoglobin but have a more pronounced sarcoplasmic reticulum. This makes it possible to release and also reabsorb a large number of calcium ions very quickly, which means that high performance can be achieved very quickly.

However, these fibers also consume more energy and tire more quickly than the slowly twitching fibers. This type of muscle fiber is found primarily in muscles that are geared to fast, short-duration activities. For example, sprinters usually have a high proportion of white muscle fiber cells.

Injuries

If a muscle fiber suddenly undergoes a very strong stretching and the connective tissue is no longer strong enough to absorb it, a muscle fiber tear may occur.This injury is a very painful event and is often described by those affected as a sensation similar to a knife wound. Usually the tear is palpable as a depression and is accompanied by bruising. Tears in the muscle fibres of the calf muscles are particularly frequent, as these are exposed to particularly high loads, especially the dangerous braking movements.

The treatment of a torn muscle fiber is based on the PECH principle: P for pause, E for ice, C for compression and H for elevation. If this therapy is carried out early, a torn muscle fibre normally heals on its own within a few days without further complications and consequences.