1. Muscular system: Fibre types and contractions
BTEC L3 Sport
Kevin Browne

2. Aims of the lesson Outline the types and difference of fibre types
To identify the main function of the muscular system
Outline and describe the roles of muscle in order to provide it main function

3. Task
Individually write your own description of what a slow twitch fibre
Key words may include
Contraction
Endurance
Energy production
Force production

4. Slow twitch fibre
These will be red in colour as they have good blood supply. They will have a dense network of blood vessels making them suited to endurance work and they are slow to fatigue
They contain many mitochondria to make them more efficient at producing energy using oxygen

5. Individually write your own description of what a fast twitch fibre
Use the same keywords as before
FTF will contract as twice as quick as STF and are thicker in size. They have a poor blood supply and are whiter in appearance and will fatigue quickly.
They are harder faster contractions making them suitable for sprinters

6. What's the difference between type 2a and 2b
The type that is used depends upon the chosen activity. Type 2b fibres work when a person is very close to their maximum intensity.
Type 2a work at slightly lower intensities but still much higher than slow twitch fibres
Can you give me an example of this?

7. Characteristics
Slow twitch (T1)
Fast oxidative glycolytic F.O.G (T2A)
Fast twitch glycolytic. F.T.G. T2B
Speed of contractions
Force of contractions
Size
Mitochondrial density
Myoglobin density
Fatigability
Aerobic capacity
Capillary density
Anaerobic capacity
Motor neuron size

8. Characteristics
Slow twitch (T1)
Fast oxidative glycolytic F.O.G (T2A)
Fast twitch glycolytic. F.T.G. T2B
Speed of contractions (ms)
Slow (110)
Fast (50)
Force of contractions
low
High
Size
Smaller
Large
Mitochondrial density
Lower
Low
Myoglobin density
Fatigability
Fatigue resistant
Less resistant
Easily fatigued
Aerobic capacity
Medium
Capillary density
Anaerobic capacity
Motor neuron size
Small

9. Contracting muscles What is the main function of muscles?
Simply movement
When a muscle contracts it pulls on the tendon which in turn pulls the bone and makes the bone
When muscles contract they work as a group in that the muscles contracting is dependent on the other muscles doing their job
A muscle can play one of the four roles

10. 4 roles
Agonist (prime mover): the muscle contracts to produce the desired movement
Antagonist : this muscle relaxes to allow the agonist to contract
Synergist : this muscle assists the agonist in producing the desired movement
Fixator :these muscles will fix joints and the body in position to enable the desired movement to occur.

11. During the upward phase of the bicep curl the biceps are the agonist and are contracting concentrically. During the downward phase the biceps are still the agonist but this time they are contracting eccentrically. They are in effect acting as a brake, resisting gravity to control the downward phase of the exercise.
This is sometimes a difficult concept to understand and you may find it useful to try the exercises and feel how the muscles are working.

12. Movement Agonist Antagonist Fixator Synergist Elbow Flexion Biceps
Triceps
Deltoids
Brachialis
Get the students to think of other examples after going through this with them as a class

13. Concentric
Eccentric
Muscle length
Shortens under tension
Lengthens under tension
Effect on movement
Causes movement
Controls movement
Example 1
Bicep curl upward phase
Bicep curl lowering phase
Example 2
Leg extension
Upward phase of a lateral pull down the biceps and latissimus dorsi are controlling the movement

14. Summary
Questions
You tell me!
True or false