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Muscle Fibre Types

And muscular contractions

+Key Concepts

Muscles consist of slow-twitch and fast-twitch fibres. These fibres are suited to certain types of physical activity and assist with an athlete’s capacity to create forceful or sustained muscle contractions.

Muscle contractions can be isotonic (concentric and eccentric) and isometric

+Muscle fibre types

There are two basic types of muscle fibres we have in the body Fast twitch (2 types) and slow twitch

Most people would have about a 50:50 split of the two different types

Each fibre is better suited to a different type of activity (based on its intensity)

+Slow Twitch (Type 1 fibre)

Red in colour

Contract slowly over a longer period of time

Best suited to aerobic and endurance type activities

Exert less force and can contract repeatedly

+Fast Twitch (Type 2a)

Very similar characteristics to Slow Twitch fibres

Have the ability to contract very forcefully over a longer period of time

+Fast Twitch (Type 2b)

While in colour

Contract rapidly over a shorter period of time

Best suited to anaerobic and high intensity activities

Exert great force in bursts of power and speed

+Athletes and their fibre types

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Types of muscle contractions

+Overview

There are three types of muscles contractions classified by the movement they cause Isotonic Isometric

+Isotonic

The most common type of contraction

Occurs when there is a change in muscle length as tension is developed

Muscle is shortening = isotonic concentric

Muscle is lengthening = isotonic eccentric

+Isometric

This type of contractions is characterised by the muscle contracting without causing movement.

Example: Holding your body in a squatting position

It is quite difficult to maintain this contraction for a long period of time