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Anatomy for Sport Science: Muscles
In this assignment I am going to be talking about the different types of muscles within the
body
There are three different types of muscles within the human body
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The three types of muscle include; Cardiac, smooth and
skeletal muscles
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This means that the
muscles movement cannot be actively controlled, for example, we cannot control how our
heart (cardiac muscle) beats ourselves, through thinking about the action
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Like its name suggests, Smooth muscle has a smooth
appearance
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This muscle type is controlled by
the Autonomic Nervous System (ANS), causing slow
rhythmical contractions, aiding the passage of food
down the oesophagus, for example
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This type of involuntary
muscle has a very specialised function and is again under control of the Autonomic Nervous
System (ANS)
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The
cardiac muscle has its own pacemaker, which can create its own nervous impulses, this is
called autoythmicity
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A large number of Mitochondria, Myoglobin and a constant blood flow, increases
the rate of aerobic respiration within the heart muscle leading to high contractile strength
and endurance
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Within sport the cardiac muscle is vital as it pumps,
oxygen and nutrient rich blood around the body, supplying all of the
other working muscles
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Now, I will talk about the Skeletal muscles, these voluntary muscles are attached to our
bones via tendons
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When the muscles are receiving messages from the Central nervous
system (CNS) the muscle will contract, and then when these signals stop, the muscle relaxes
again
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As
you can see in the diagram, there are many nuclei
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Actin and Myosin are responsible for muscle contraction
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The different types of muscle
fibres are categorised into Type I, Type IIa and
type IIb, they are all identified by their
characteristics such as the speed of their
contractions
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Slow twitch fibres are
used during movement which requires continuous muscle contractions over a long period of
time, such as running a marathon or long distance cycling, and are therefore adapted to low
intensity aerobic exercise
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Alongside Myoglobin, a protein which oxygen binds to provide the muscle with extra
energy
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This type of fibre can work both
aerobically and anaerobically (with or without oxygen) in order to produce movement
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This allows
fast contractions over a longer period of time
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Type IIb muscle fibres
have the highest rate of contraction however they fatigue very quickly
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These stores are used up very quickly, leading to fatigue
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If we look at Muscle twitch fibres in relation to different sports people and the sports that
they compete in, we can determine the proportions of the different types of twitch fibre
that each different individual may have
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This may
explain why some individuals excel at particular sports naturally, due to the proportions of
Twitch fibres that they have
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I would have inherited
some of Slow twitch fibres however, because I train aerobically, my body and fibre types will
have adapted over time
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This may suggest that I also naturally have
a fair amount of Type IIb fast twitch fibres too, which would have been genetic as I have

never really done any anaerobic training
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If we look at a voluntary muscle it is made up of numerous muscle fibres bundled together,
into what we call fascia
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Nerves are intertwined with the muscle fibres
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When the brain sends out a signal, it travels along the nerves to these fibres
telling them whether to shorten (contract), lengthen (relax) or tense
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When a nervous impulse arrives at the neuromuscular junction a chemical called
Acetylcholine is released, causing Calcium ions to be released
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Now, the Troponin
can bind to another protein called Tropomyosin, which spirals around the Actin filaments
active site
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This allows Myosin to then move in and Bind to the Actin filament forming a
Crossbridge
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The distance between the Z lines is reduced
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Skeletal muscles are often arranged in Antagonistic pairs
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The
muscle within the pair that is contracting is often called the Agonist whilst the muscle that is
relaxing would be known as the Antagonist
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The Synergist stabilises the joint that is in use by assisting the agonist
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For example, the Brachioradialis
and the brachialis assist the biceps during a bicep curl by stabilising the elbow joint
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In order for the Agonist to achieve its maximum, the
fixator stabilises the origin
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Types of Contractions
The brain sends impulses to the muscles, these impulses tell the muscles to pull on bones
(contract) that they are closely attached to in order to produce movement
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During Isometric contractions the muscle stays the same length as it works, as a result of
this there is no movement
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Concentric contractions cause the muscle that is working to shorten under a load or tension
as the origin and insertion move closer together
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For example, when performing a squat
exercise, the Quadriceps lengthen on the way down
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On the
way back up, a concentric contraction occurs, as the Quadriceps shorten
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These movements are generally exercises that are used to test
and improve strength within the muscles
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These include, contractibility, elasticity,
excitability and extensibility
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For example, we can look at how forcefully
the muscles are able to contract within a sprinters legs during a 100m race
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Muscle elasticity is all about stretch recoil
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So for example,
before we exercise we stretch the muscles, in order to warm them up, they also return

straight back to their normal shape as soon as the body returns to a neutral position and the
muscles cool back down
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This means that a muscle is able to respond to a specific stimuli
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This for example, is seen within a lot of people who
practice yoga as well as gymnastics
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When a muscle has high excitability, it will also cause a larger number of muscle fibres to
contract, at a faster rate
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Therefore, where the excitability of a muscle is high, so
is the contractibility
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This is definitely beneficial for a sprinter, who
wants to create fast, powerful movements for short periods of time
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This means that they are activated when the muscle first contracts
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For example, the soleus, contains a larger number of slow
twitch fibres as although it allows plantar flexion of the foot to take place, it also works to
extend and support the knee
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This means that the
muscle is able to continue to contract to a number of different lengths
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The degree of extensibility will be higher in the muscles of an individual, who uses more
slow twitch muscle fibres, in exercises such as yoga or sports such as gymnastics and some
martial arts
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Also if a muscle is contracting slower, it will be able to extend further than a muscle
that is moving through a rapid contraction
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Those individuals who compete in sports such as deadlifting,
boxing and sprinting, involving more fast twitch muscle fibres, are not likely to have good
extensibility as they only require the muscle to contract to a certain degree, for a short
period of time
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One common link between all of the muscles within the body is they all have some degree
of elasticity
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The only
difference here is the speed at which they do so
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This is linked to the
excitability of the muscles and how fast they allow the muscle fibres slide
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