MyoBravo Bedienungsanleitung / Operators Manual
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Fibres of type IIa are therefore capable of fast contractions, which are marked
by a significant expenditure of energy, that should also be maintained for long
periods of time. The fibres are therefore relatively resistant to tiredness.
Type IIb (white muscular system)
This type is also known as FG-fibres (fast twitch glycol fibres – fast contract-
ing fibres with glycolytic metabolism). This fibre is stimulated by a phasal
motoneuron with a cellular body
and a very big axon
that transmits impulses
into the muscle at very high velocity. These fibres are white and contain a high
level of glycogen and glycolytic enzymes, that enables them to release a high
level of anaerobic energy. The contraction is quite fast and produces great
power. Due to lack of mitochondrion, these fibres will not be able to endure
long-lasting activities and fatigue easily, especially in an untrained muscle. Fi-
bres of type IIb play a very important role in all human activities, which re-
quire an explosive expenditure of energy, e.g. sports like sprinting, weight lift-
ing, swimming, jumping etc.
Spread of muscular fibres
Nearly all human muscles show a mixed form of different fibre types. The
aforementioned types of fibres appear in diverse percentages in the muscles.
The relation between fibres of Type I and Type II can vary considerably. The
muscles for posture (back and stomach muscular systems) show a higher
proportion of Type I fibres, whereas muscles for movement / motion (leg and
arm muscular systems) usually consist mainly of Type II fibres.
