Skeletal muscles are responsible for running, weight lifting, swimming, snooker, whatever the sport, and that is correct, but within our muscles there are fibres which have their own job to do, and depending on the activity, different muscle fibres are used. For example a long distance runner will use different muscle fibres than a sprinter.
The muscle fibres are in three categories, Type 1 and Type 2, but Type 2 can be further divided into Type 2a and Type 2b.
The muscle fibres adapt to whichever activity we are doing without us being aware of it.
Type 1 muscle fibres are also known as slow twitch fibres.
Type 1 or slow twitch fibres, contain lots of blood vessels and need a rich supply of oxygen in the blood to give lasting energy, for example long distance runners can keep going for a long time before they become fatigued.
Type 2 muscle fibres along with Type 2a and Type 2b are known as fast twitch fibres.
Type 2 or fast twitch fibres use anaerobic metabolism which means the body can produce energy without oxygen. This happens when using short bursts of energy for example using weights or sprinting.
Type 2a or fast twitch muscle fibres are a combination of slow twitch and fast twitch fibres. They use both oxygen and anaerobic metabolism to produce energy.
Type 2b or fast twitch muscle fibres use anaerobic metabolism but are the quickest to fatigue, however they produce immense power in fast bursts of strength or speed.
So to summarise, Type 1 fibres are for marathons or cycling, and Type 2 fibres including type 2a and 2b for running to catch the bus!