Transcript Muscle fibres

Muscular system recap.
Classifications of muscles
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There are three types of muscle you
need to know.
Cardiac muscle
Skeletal muscle
Smooth muscle
Cardiac muscle
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Found only in the
heart.
Not under our
control
The muscle cells
look like one big
line
Smooth muscle
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The muscle cells
are spindle shaped.
Located around the
major organs.
Muscle is not under
our control.
Skeletal muscle
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Muscle is attached to
the bone via tendons.
The muscle cell is
spindle formed and
consists of fibres the
overlap.
When electricity is
induced to the muscle
fibres they become
shorter.
The muscles cells are
voluntary, (under our
control).
Using muscles
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Muscle fatigue
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Muscle atrophy
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When your using your muscles a lot and they don’t
get enough oxygen, they become tired or FATIGUED.
If you don’t use your muscles enough they become
smaller and wasted, this is called MUSCLE ATROPHY.
Cramp
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A sudden contraction of a muscles that wont relax,
caused by a lack of blood supply to the muscle.
The sliding filament theory
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The sliding filament theory is very
complex, but can be simplified by
thinking of the muscles like a giant
comb, the teeth of the come are the
muscle fibres and when the muscle
contracts these fibres overlap pulling
the tendons together making the
muscle shorter.
Antagonistic - agonist
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Muscles can only pull, because of this
they must work in pairs.
When one muscle contracts to move
the skeletal system this is called
agonist.
The muscle that relaxes is called the
antagonist.
The purpose of tendons
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Tendons are
formed at the end
of the muscles and
attach the muscle
to the bone
allowing the body
to move.
The purpose of ligaments
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Ligaments are
designed to
support joints by
attaching to both
bones making the
joint secure during
twisting and
stretching
movements during
sport.
Types of muscle contraction
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Isometric contraction
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Muscle stays the length, its like trying to
move an immoveable object.
Isotonic contraction
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When the muscles move and (become
shorter and longer) just like weight lifting.
Muscle Fibre Types
Learning Outcomes
By the end of this session you should
be able to:
1. Identify 3 different types of fibres
2.
3.
Describe the characteristics of each
type
Identify which sports use each type
Muscle Fibre Types
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Muscles are composed of thousands and
thousands of individual muscle fibres
Not all fibres are alike in structure and
function
Can be classified into 3 types:
• Type I
• Type IIA
• Type IIB
Type I Fibres
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Slow twitch or slow oxidative fibres:
Red in colour
Large amounts of mitochondria,
myoglobin and capillary network
Work slowly (split ATP at a slow rate)
Able to repeatedly contract or maintain
contraction for a long duration
High resistance to fatigue
Fibres work mainly aerobically
Type IIA Fibres
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Fast twitch or fast oxidative glycolytic
fibres (FOG)
Similar to Type I Fibres
Red in colour
Large amounts of myoglobin, many
mitochondria and capillaries
Resistant to fatigue
Work rapidly to split ATP, fast contraction
speed
Work aerobically or anaerobically
Used in high intensity, short duration
activities such as 200m swim or 800m
Type IIB Fibres
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Fast twitch or fast twitch glycolytic (FTG)
fibres
White in colour
Low number of myoglobin, few
mitochondria, few capillaries
Fatigue easily
Fast contraction speed, split ATP quickly
Much stronger force of muscle contraction
These are used for activities of a very high
intensity (anaerobic)
• e.g. powerlifting or 100m sprint
Fibre Mix
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Most skeletal muscle is a mixture of
all 3 types
Proportion of types varies in relation
to usual action of the muscle
For example – the postural muscles
of the neck and back and leg have a
higher proportion of Type I Fibres
Why do you think this is?
Fibre type and athletic success
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Some outstanding
athletes have a much
higher percentage of
whatever fibre type is
most advantageous to
their event
Elite distance runners
- calf muscles
composed of 90%
slow twitch (Type I)
fibres
Fibre type and athletic success
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Sprinters - 92% fast twitch (Type II)
fibres
What role does genetics play in
determining this?
The slow and fast twitch
characteristics of muscle fibres
appear to be determined early in life,
perhaps within the first few years
Fibre type and athletic success
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Studies have revealed that identical twins
have nearly identical fibre compositions
Little evidence showing change of fibre
type from a few weeks training
More recent evidence suggests the
possibility of fibre type change with high
volume of training
However, the percentage of change is too
small to make a difference in sports that
require a high percentage of one fibre
type to another
Effects of Exercise on Fibre
Type
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Can change the characteristics of some
fibre types
Some Type IIB fibres can transform into
Type IIA fibres with long distance
endurance training
Prolonged endurance training has been
shown to increase the diameter of Type
IIB fibres, increase the no. of
mitochondria within the fibres, and
increase the capillaries surrounding the
fibres
The fibres can then use the aerobic energy
system more efficiently
Effects of Exercise (cont)
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Strength training
can increase the
size of Type IIB
fibres (greater
muscle mass hypertrophy)
No increase in the
number of fibres