What does muscle fibre do in skeletal muscle?
Muscle fibres are multinucleated cells responsible for muscle contractions. Each muscle has between 10 000 and 450 000 fibres. There are two main types that can be distinguished by their colour. Red muscle fibres (also called Type 1 or slow-twitch fibres) acquire their colour from their good blood supply and high myoglobin content. They fatigue slowly, and use glycogen and fat as their fuels. White muscle fibres (also called Type 2 or fast-twitch fibres) have a more moderate blood supply, only use glycogen as fuel, and fatigue more quickly than the red fibres. However, they are bigger than the red fibres and their contractions are much more powerful. Red muscle fibres are adapted for aerobic activities of long duration. White fibres are adapted for short bursts of explosive anaerobic activity.
