Transcript Muscle Fibre Types

Muscle Fibre Types
There are two kinds of muscle
fibres
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Slow-twitch: red/dark in colour
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Generate tension slowly
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Relax slowly
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Able to maintain a lower level of tension for a
long duration
Useful during activities such as long-distance
swimming, cycling and running
Slow-twitch cont...
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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
What is an enzyme?
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An enzyme is a protein that acts as a catalyst
for chemical reactions
The enzyme itself is not affected by the
chemical reaction
Fast-Twitch Muscle Fibres
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More pale in colour
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Tense and relax quickly
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Can generate large amounts of tension for short
periods of time
High level of myosin ATPase and glycolytic
enzymes
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Activate 2-3x faster than slow-twitch fibres
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Short sprints, powerlifting, explosive jumping
The Importance of Myoglobin
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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
Three Fibre Types
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1 type for slow-twitch
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2 types for fast-twitch
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Type I or Slow-Oxidative (SO): these muscles
generate energy slowly
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More fatigue-resistant
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Depend on aerobic processes
Type IIA
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Type IIA or Fast-Oxidative Glycolytic (FOG)
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Intermediate
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High-speed energy release
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Glycolytic capacity
Type IIB
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Type IIB or Fast-Glycolytic (FG)
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Store a lot of glycogen and high levels of enzymes
necessary for quick contraction
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Does not require oxygen
The Distribution of Muscle
Fibre Types
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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
Tonic Muscles
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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
Phasic Muscles
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Higher % of type IIA and IIB fibres
i.e. The biceps – key muscle for lifting and
power in the arm
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Lower % of type I
How Do I Find Out My Muscle
Type?
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The only way to find
out what percentage
of muscle fibre types
are found in your
muscles is to have a
biopsy performed :(
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Must acquire a tissue
sample
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Take out a small
portion of the muscle
and placing it under a
microscope
Fibre Type and Athletic
Performance
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Read this section on page 93 of your textbook
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Answer the following questions:
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Give an example of a sport that requires fasttwitch 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)
Questions cont...
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Endurance athletes train their muscles to?
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The goal of an endurance workout is to?
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What is the outcome of endurance workouts?