Transcript Fast Twitch Fibres

• Types of muscle fibre.
• Muscle fibres & Sport.
• How muscles work in pairs.
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9
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Deltoid
Trapezius
Biceps
Triceps
Latissimus
Dorsi
Gluteals
Abdominals
Hamstring
s
Quadriceps
Gastrocnemius
Types of Muscle Fibre
There are two different types of muscle fibre which can be found in
muscles.
•Fast twitch fibres.
•Slow twitch fibres.
Fast Twitch Fibres
These contract faster than slow
twitch fibres & with much more
force. They are used whenever
rapid, powerful movements are
needed. They do not have a
good supply of oxygen, so they
tire very quickly. They are
suited to activities that need
bursts of strength & power
such as sprinting &
weightlifting.
Slow Twitch Fibres
These work for long periods
of time because they have a
good supply of oxygen. Slow
twitch fibres are not as big or
as strong as fast twitch
fibres, & they also take
longer to contract. They are
most suited to activities that
need endurance such as
long-distance running &
cycling.
Every muscle contains a mixture of these different fibres.
For example, in the gastrocnemius, there is a high percentage of fast
twitch muscles.
Athletes will have a different mix of fast & slow twitch fibres
depending on the sport they play. Distance runners have about 80%
slow twitch fibres while some weight lifters have 80% fast twitch
fibres.
activity
marathon
cross country skiers
cyclists
800m runners
untrained
shot putters
sprinters
average % ST
81
64
59
52
47
39
40
range of % ST
50
52
52
40
42
19
20
- 98
- 75
- 72
- 62
- 76
- 57
- 53
The table above shows the average % & range of slow
twitch muscle fibres in sports performers. Use the data
to explain the differences in muscle fibre relevant to the
events they perform.
How Muscles Work
Muscles usually work in pairs or groups.
To flex the elbow the biceps contracts & the triceps relaxes.
To extend the elbow the biceps relaxes & the triceps
contracts.
This is called ANTAGONISTIC MUSCLE ACTION. The
working muscle is called the prime mover or agonist.
The prime mover is helped by other muscles called synergists.
These contract at the same time, reducing unnecessary
movement when the prime mover contracts.
Muscle Action
Study the sequence of photogr aphs of the standing long jump
& deter mine the state of contr action/ r elaxation of the
Quadriceps, Hamstr ings & Gastr ocnemius muscles. Place an
‘X’ in the appr opr iate spaces in the table to indicate which
muscle is contr acted, & which is relaxed in the var ious
positions.