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Muscle fibers

It is known that the quality of the contraction of a muscle depends, essentially, on the percentage of the type of fibers that compose it. The endowment or the percentage distribution of the different muscle fibers is genetically determined

(Weineck 2001).

There are two main types of muscle fibers:

Red type I fibers, thin and slow called ST (slow twitch = slow-twitch fibers).These fibers intervene in low-intensity muscular work (high oxidative capacity, low glycolytic capacity).Their capillarization is 4.8 capillaries, on average, per fiber.

White type II fibers, clear, thick and rapid called FT (fart twitch = fast-twitch fibers).These fibers come into action in intense muscular stress and rapid force. Their capillarization is 2.9 capillaries, on average, per fiber.

There are three sub-categories of FT fibers, namely:

1 Type IIa fibers (oxidative-glycolytic capacity);

2 Type IIb fibers (high glycolytic capacity);

3 Type IIc fibers (high oxidative capacity and good glycolytic capacity, also called intermediate fibers).

According to some research, champion athletes enjoy a genetic privilege. The research has discovered a DNA gene called "alpha-actinin-3" that controls the production of actinin in muscle, a key constituent of fast-twitch fibers. The alpha-actin-3 gene exists in two main alternative forms, called “alleles”, given as a gift by each of the parents, which can be the same or different, can be presented with a double pair

 of RR alleles, determine the presence of the sprint protein in the muscle;

 of XX alleles, do not command the production of actinin;

 of RX alleles, partial actinin production, majority of the population