slow & fast twitch muscle fibres

What slow twitch muscles fibres are:

Slow twitch muscle fibres are fibres specifically adapted for long periods of exercise. They are specialised for slow, more sustainable contractions. Slow twitch fibres mainly respire aerobically.

Examples of slow twitch muscle fibres:

Muscle fibres from a chicken or cows leg. Muscle fibres found in the thighs of marathon/long distance runners.

Key features of slow twitch muscle fibres:

• They are red/dark, meaning they contain a large amount of myoglobin
• They contain a large number of mitochondria
• Have little sarcoplasmic reticulum
• A low glycogen content
• A large amount of capillaries
• They are fatigue resistant

What fast twitch muscle fibres are:

Fast twitch muscle fibres are muscle fibres specifically adapted for rapid, intense contractions. Almost completely respire anaerobically. Panic muscles fibres.

Examples of fast twitch muscle fibres:

In the wings of a chicken, in the legs of a sprint/short distance runner.

Key features of fast twitch muscle fibres:

• Pale in colour, so have a small amount of myoglobin
• Only contains a few mitochondria
• Extensive amounts of sacroplasmic reticulum
• High glycogen content
• Only have a few capillaries
• Fatigue quickly