Types of muscle fibre Flashcards
What are the 3 types of muscle fibre?
Slow twitch muscle fibres (aerobic)
- Type 1 (slow oxidative/slow twitch)
Fast twitch muscle fibres (anaerobic)
- Type 2a (Fast oxidative glycolytic)- FOG
- Type 2x (fast twitch glycolytic)- FTG
Facts
1) All muscles in the body contain all 3 types of muscle fibre- the proportions are determined at birth.
2) Av. proportions throughout the whole body is around 50% slow twitch and 50% fast twitch.
3) Muscle fibres are grouped into motor units.
4) Training can slightly affect these proportions.
Characteristics of Type 1 muscle fibres pt.1
1) Large stores of triglycerides
2) Slow contraction time
3) Low amounts of force produced
4) Small motor neuron size
5) High aerobic capacity
6) Low anaerobic capacity
Characteristics of Type 1 muscle fibres pt.2
7) High myoglobin levels
8) High capillarisation
9) High oxidative enzyme activity
10) High mitochondria levels
11) Better adapted to low intensity, long duration endurance work
12) Low fatigability
Characteristics of Type 2a muscle fibres (FOG) pt.1
1) Large stores of Glycogen and Glycolytic enzymes (PFK)
2) Fast contraction time
3) Powerful contraction
4) Large motor neuron size
5) Medium aerobic capacity
Characteristics of Type 2a muscle fibres (FOG) pt.2
6) High anaerobic capacity
7) Better adapted for high intensity endurance events (1 mile run)
8) Medium fatigability
9) High glycolytic enzyme activity
10) FOG fibres have a larger diameter
11) Large motor unit
Characteristics of Type 2x muscle fibres (FTG) pt.1
1) Large stores of PC- increasing the potential for short term regeneration of ATP
2) Fastest contraction time
3) Powerful contraction
4) Large motor neurone size
5) Low aerobic capacity
Characteristics of Type 2x muscle fibres (FTG) pt.1
6) Very high anaerobic capacity
7) High fatigability
8) Better adapted for explosive events (100m sprint)
9) High glycolytic enzyme activity
10) FTG fibres have a larger diameter
What does FFEESSO stand for?
F- Fatigability
F- Force of contraction
E- Energy source
E- Enzyme activity
S- Speed of contraction
S- Size of motor neuron
O- Oxygen used?
What are the functional aspects of muscle fibres?
- Contraction speed
- Force produced
- Aerobic capacity
- Anaerobic capacity
- Fatigability
- Glycolytic enzyme activity
- Oxidative enzyme activity
- Motor neurone conduction capacity
What are the structural aspects of muscle fibres?
- Motor neurone size
- Mitochondrial density
- Myoglobin content
- Capillary density
- PC stores
- Glycogen stores
- Triglyceride stores
Training and muscle size
Any increase in size as a result of training is due to an increase in the size of fibres not number.
Hypertrophy occurs due to the following factors:
Hypertrophy- following power and strength training (anaerobic)
- Increased size and number of myofibrils.
- Increased sarcoplasmic volume- fluid that allows for better conductivity (increased strength of contraction)= ATP-PC + AGS
- Increased stores of ATP, PC and Glycogen
Hypertrophy- following endurance training
- Tearing will occur
1. Increased capillarisation
2. Increased number and size of mitochondria
3. Increased myoglobin stores
4. Increased glycolytic enzymes
Effects of training on types of muscle fibre- endurance training
- Endurance training can result in a small % of fibres being converted from Type 2x (FTG) to Type 2a (FOG).
- An excess of endurance training can lead to a loss of speed.
