Muscle Fibre Types

Question 1

Fibre types

Answer 1

Type 1
Type 2a
Type 2b

Question 2

Type 2a - fast twitch (ONLY TOP 3 + EG IMPORTANT)

Answer 2

Intermediate speed of contraction
Moderate force of contraction
Fatigue resistance (but not as much as type 1)
e.g. 400m sprint
Possess some aerobic characteristics and can develop aerobic characteristics
White

Question 2

Type 2b - fast twitch (ONLY TOP 3 + EG IMPORTANT)

Answer 2

High force of contraction
Rapid contraction speed
Low resistance to fatigue
e.g. 100m sprint
Purely anaerobic
White

Question 3

Type 1 - slow twitch (ONLY TOP 3 + EG IMPORTANT)

Answer 3

Slow contraction speed
Low force of contraction
Fatigue resistant
e.g. Marathon runner
Aerobic energy system
Contract repeatedly
Red

Question 4

size of neuron necessary for activation

Answer 4

The greater the diameter of the fibres, the larger the neuron needed to activate the muscle fibres

Type I muscle fibres have small diameters so stimulation from a small neuron.

Type IIa muscle fibres have intermediate-size diameters so stimulation from an intermediate-size neuron.

Type IIb fibres have a large diameter and need a large neuron to stimulate them.

Question 5

stimulus threshold

Answer 5

During low-intensity exercise, type I fibres are predominantly recruited as their fibre is small in diameter so the threshold is low

At higher level intensity, type IIa fibres are predominantly recruited as the fibre is larger in diameter so it has a higher stimulus threshold as it needs a larger neuron to stimulate

At very high-intensity exercise, type IIb fibres are predominantly recruited as the fibre is very large in diameter so its threshold is the highest of all three as it needs a larger neuron to stimulate

Question 6

role of genetics

Answer 6

Athletes with a high percentage of Type II fibres (80% +) are likely to be better at power/speed/explosive type events.
Athletes with a high percentage of Type I fibres (80% +) are likely to be better at endurance events.