TeachPE.com
Teach PE



Sports Coaching

A LEVEL PE


GCSE PE



Home > Anatomy & Physiology > Muscle fiber Types

Muscle Fiber Types

 

Within skeletal muscle there are three types of fiber:

Type I

Type I fibers are also known as slow twitch fibers. They are red in colour due to the presence of large volumes of myoglobin and so oxygen and high numbers of Mitochondria. Due to this fact they are very resistant to fatigue and are capable of producing repeated low-level contractions by producing large amounts of ATP through an aerobic metabolic cycle.

For this reason the muscles containing mainly type I fibers are often postural muscles such as those in the neck and spine due to their endurance capabilities Also, athletes such as marathon runners have a high number of this type of fiber, partly through genetics, partly through training.

Type IIa

Type IIa fibers are also sometimes known as fast oxidative fibres and are a hybrid of type I and II fibers. These fibers contain a large number of mitochondria and Myoglobin, hence their red colour. They manufacture and split ATP at a fast rate by utilising both aerobic and anaerobic metabolism and so produce fast, strong muscle contractions, although they are more prone to fatigue than type I fibers. Resistance training can turn type IIb fibers into type IIa due to an increase in the ability to utilise the oxidative cycle.

Type IIb

Often known as fast glycolytic fibers they are white in colour due to a low level of myoglobin and also contain few mitochondria. They produce ATP at a slow rate by anaerobic metabolism and break it down very quicky. This results in short, fast bursts of power and rapid fatigue. As mentioned above, this type of fiber can be turned into type IIa fibers by resistance training. This is a positive change due to the increased fatigue resistance of type IIa fibers. These fibers are found in large quantities in the muscles of the arms.

Now Test Yourself

1. Which type of fibers make up the majority of postural muscles?










Flip card >

1. Which type of fibers make up the majority of postural muscles?



  • Slow twitch







Next Card >

2. Type 2a fibers are red in colour due to the high content of what?










Flip Card >

2. Type 2a fibers are red in colour due to the high content of what?



  • Mitochondria and myoglobin






Next card >

3. Type 2b fibers are often called what?











Flip Card >

3. Type 2b fibers are often called what?



  • Fast glycolytic







Next card >

4. Can training cause changes in muscle fiber type? If so, which?










Flip Card >

4. Can training cause changes in muscle fiber type? If so, which?



  • Yes, type 2b can change to type 2a






Next card >

5. Marathon runners would have more of which type of muscle fibre?










Flip Card >

5. Marathon runners would have more of which type of muscle fiber?




  • Slow twitch (type 1)




Start again with first card >



 

Next - Shapes of muscles >>

Sprinters have fast twitch fibres

Resources:


Learn More About:
   
 

Find us on Facebook

Teach PE