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Unit 1 Task 2.B
Functions of the muscular system
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Antagonist pairs: Antagonist muscle pairs work together to create
movement. When the prime mover the agonist contracts the antagonist
relaxes. These types of muscles work in pairs such as the biceps and the
triceps in the arm and the quadriceps and hamstring in the leg.
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Synergist: Synergist contractions in a muscle stabilises a joint that
movement is occurring in. example in a bicep curl the synergists help
stabilise the elbow joint and help movement take place. It is the
brachioradialis and brachialis that help stabilise the joint in a bicep curl.
Fixator:The fixator muscles stabilize a section of the body when
another section moves. The muscle allows the antagonist muscles to move
effectively during normal movement or exercise Some muscles attach to
one or more bones. When a person performs a bicep curl, for example,
the bicep flexes the elbow. The bicep connects to the bone in two places,
and the fixator allows one area to move during the curl. As the bicep
contracts, the radius and scapula come together. The fixator muscle
prevents the scapula from moving in order to achieve full movement of
the radius area.
Types of contraction
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Isometric: Isometric contractions occur when there is no change in the
length of the contracting muscle. This can occur when you are carrying an
object in front of you as the weight of the object is pulling your arms down
but your muscles are contracting to hold the object at the same level .The
amount of force a muscle is able to produce during an isometric contraction
depends on the length of the muscle at the point of contraction.
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Concentric: Concentric contractions are those which cause the muscle to
shorten as it contracts. An example is bending the elbow from straight to fully
flexed causing a concentric contraction of the Biceps. Concentric contractions
are the most common type of muscle contraction and occur frequently in
daily and sporting activities.
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Eccentric: Eccentric contractions are the opposite of concentric and occur
when the muscle lengthens as it contracts. This is less common and usually
involves the control or deceleration of a movement being initiated by the
eccentric muscles agonist. For example, when kicking a football, the
Quadriceps muscle contracts concentrically to straighten the knee and the
Hamstrings contract eccentrically to decelerate the motion of the lower limb.
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Isokinetic: Isokinetic contractions are similar to isotonic in that the
muscle changes length during the contraction, where they differ is that
Isokinetic contractions produce movements of a constant speed.
Fibre Types
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Type 1: Type 1 muscle fibres are known as slow twitch fibres. They
contain high amounts of myoglobin, oxygen and mitochondria having high
amounts of these make the muscles more resistant to fatigue. This means
that type 1 muscle fibres are best suited to long distance sports such as
running or cycling because they don't fatigue as fast as other muscle
types.
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Type 2a: Type 2a fibre types are known as fast twitch oxydative fibres.
These fibres contain a large number of mitochondria and Myoglobin
similar to type one fibres but without the oxygen. They manufacture and
split Adenosine triphosphate at a fast rate by utilising both aerobic and
anaerobic metabolism and so produce fast, strong muscle contractions,
although they are more prone to fatigue than type I fibres. Type 2a fibres
are in the middle of fast twitch fibres and slow twitch fibres. They are
best suited to sports such as 400/800m as they don't fatigue as fast and
they can maintain speed they cant go as long as fast twitch fibres.
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Type 2b:
Type 2b fibres are known as fast twitch glycolytic fibres
which means that they fatigue fast. They produce ATP at a slow rate by
anaerobic metabolism and break it down very quickly This results in short,
fast bursts of power and rapid fatigue.