1. Muscle Fibre Types

2. There are two kinds of muscle fibres
Slow-twitch: red/dark in colour
Generate tension slowly
Relax slowly
Able to maintain a lower level of tension for a long duration
Useful during activities such as long-distance swimming, cycling and running

3. Slow-twitch cont...
Have low levels of an enzyme called myosin ATPase – used to provide instant energy for muscle contraction
Also have low levels of glycotic enzymes which allow the release of glycogen within muscles

4. What is an enzyme?
An enzyme is a protein that acts as a catalyst for chemical reactions
The enzyme itself is not affected by the chemical reaction

6. Fast-Twitch Muscle Fibres
More pale in colour
Tense and relax quickly
Can generate large amounts of tension for short periods of time
High level of myosin ATPase and glycolytic enzymes
Activate 2-3x faster than slow-twitch fibres
Short sprints, powerlifting, explosive jumping

7. The Importance of Myoglobin
The differences between muscle fibre types = the extent to which the muscle relies on oxygen in the production of energy
Myoglobin is a protein that delievers oxygen to working muscles
This allows energy-producing biochemical reactions to be sustained over a long period of time
Using aerobic processes for energy production = ability to sustain activity longer

8. Three Fibre Types 1 type for slow-twitch 2 types for fast-twitch
Type I or Slow-Oxidative (SO): these muscles generate energy slowly
More fatigue-resistant
Depend on aerobic processes

9. Type IIA Type IIA or Fast-Oxidative Glycolytic (FOG)‏ Intermediate
High-speed energy release
Glycolytic capacity

10. Type IIB Type IIB or Fast-Glycolytic (FG)‏
Store a lot of glycogen and high levels of enzymes necessary for quick contraction
Does not require oxygen

11. The Distribution of Muscle Fibre Types
A muscle's fibre makeup determines its function and at the same time what a muscle does gives us an indication of what it is made of
Use the terms tonic muscles and phasic muscles as a way to describe basic functions

12. Tonic Muscles
Assist the body with maintaining posture or stability during walking, standing, throwing, etc
High % of type I fibres (slow-twitch)‏
i.e. Soleus – performs dorsiflexion and is key in maintaining body posture

13. Phasic Muscles Higher % of type IIA and IIB fibres
i.e. The biceps – key muscle for lifting and power in the arm
Lower % of type I

14. How Do I Find Out My Muscle Type?
The only way to find out what percentage of muscle fibre types are found in your muscles is to have a biopsy performed :(
Must acquire a tissue sample
Take out a small portion of the muscle and placing it under a microscope

15. Fibre Type and Athletic Performance
Read this section on page 93 of your textbook
Answer the following questions:
Give an example of a sport that requires fast- twitch muscles fibres and an example of a sport that requires slow-twitch
How would an elite athlete maximize their performance?
What is the goal of the workout of an Olympic shotputter and a hockey player (think of the energy system they use)

16. Questions cont... Endurance athletes train their muscles to?
The goal of an endurance workout is to?
What is the outcome of endurance workouts?