Musclefibre

The Muscle Fiber Types:

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Muscle Fiber Types

Type I :Slow Twitch Fibers

-They are red in color due to the presence of large volume of myoglobin and so oxygen and high number of mitochondria.

-they are suited to endurance activity using the aerobic energy system which relies on oxygen from the blood for the supply of energy. 

-Slow twitch fibres are smaller and develop less force than fast twitch fibres.  Walking or cycling for 30 minutes at low intensity would use mostly slow twitch fibres.

Type IIA :Fast Oxidative Fibers

-Are hybrid of type I and II fibers and it has fast contraction speed and can use aerobic energy sources as well as anaerobic energy sources. 

-Fast twitch IIa fibres are ‘white fibres’ as they are less reliant on oxygen supplied by the blood for energy and therefore fatigue faster than slow twitch fibres.

-Fast twitch type IIa fibres are suited to speed, strength and power type activities, such as moderately heavy weight training (8-12 reps) and fast running events such as the 400metres.

Type IIB:Fast Glycolytic Fibers

-They are white in color due to a low level of myoglobin and also contain few mitochondria.

- Fast twitch IIb fibres contract extremely rapidly, create very forceful muscle contractions and fatigue quickly.

-fast twitch type IIb fibres are also suited to speed, strength and power type activities.  Heavy weight training (1-3 reps), power lifting, and 100metre sprints are examples of activities that predominantly require IIb fibres.

A.Type I C. Type IIbB.Type IIa

Table of Muscle FibreTypes: Type I

fibres

Type II

A fibres

Type II

B fibres

Contraction speed (ms)

Slow (90-140

ms)

Fast (50-100 ms)

Very Fast (40-90 ms)

Size of motor neuron Small Large Very Large

Resistance to fatigue High Intermediate Low

Activity Used for

Endurance type activities

Short: high intensity

activities

Very short :maximal intensity activities

Force production Low High Very High

Efficiency High Medium Low

Number of Mitochondria High Medium Low

Myoglobin content High Medium Low

What determines how many of each muscle fibres type an individual has?

1. Genetics: - You are genetically programmed to having a certain percentage of each muscle fiber based on

your parents’ genes.  

It is thought that the average person is born with around 60% fast twitch and 40% slow twitch fibres, however some individuals can be born with larger amounts of fast twitch or slow twitch fibres and may therefore be more suited to either high force or long duration activities.

2. Hormone levels within the blood:  

-The amount of hormone in the blood will affect the fibre type of an individual and how big the fibres are.

3. Training undertaken:  -Fibre type and the ability to

change fibre type is a common area of debate amongst exercise physiologists.  There is no evidence as yet to show that fibre type can be changed, however there is evidence to show that fibres adapt to the type of training they are exposed to. 

Video: Muscle Fiber Types:

More Video Info

Evaluation: Identify the kinds of muscle fiber type

Assignment:

•Research what are the different muscle shape . Write it on a whole sheet of paper(yellow paper).

References:

http://www.ptdirect.com/training-design/anatomy-and-physiology/musculoskeletal-system/skeletal-muscle-2013-anatomy-and-fiber-types

http://www.youtube.com/watch?v=0XhSlRkytkE

http://www.youtube.com/watch?v=eWySnjSzpSM