Download Anatomy for Sport and Exercise Week 4: Types of Muscular

SPORT AND EXERCISE SCIENCE
Anatomy
Muscular Contractions.
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Learning Outcomes
By the end of this session you should
be able to:
 Explain the terms origin and
insertion
 Identify at least 4 different roles of
muscles
 Explain the terms isotonic,
concentric, eccentric, isometric and
isokinetic contraction
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Ongoing Task

Try to complete worksheet 38 and 39
as we go through the lecture.
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Muscle Attachment
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Attached to bones by TENDONS
Muscles always cross at least 1 joint
(some, e.g. rectus femoris, cross 2
joints)
When a muscle contracts, the ends
are pulled towards each other,
exerting a force on the attached
bones, and producing movement at
the joints
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Origin and Insertion


The fixed attachment point is called
the ORIGIN point of the muscle (i.e.
the end of the muscle attached to a
bone that does NOT move)
The moving end is called the
INSERTION point of the muscle (i.e.
the end of the muscle attached to a
bone that does move)
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Example
Insertion
Origin
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Muscles and Movement
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Muscles can only pull, they cannot
push
They must, therefore, work in pairs
in order for movement to occur
Muscles that work together are called
ANTAGONISTIC PAIRS
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Roles of Muscles

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AGONIST (prime mover) - the muscle
that contracts to cause a movement (e.g.
the bicep muscle contracts to cause the
arm to bend)
ANTAGONIST – the opposing muscle to
the agonist (in the example this would be
the triceps)
Antagonist must relax and lengthen to
allow movement to occur (i.e. bending the
arm)
Known as RECIPROCAL INNERVATION
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Roles of Muscles (cont)
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SYNERGIST – muscles that help the prime
mover to produce the desired movement
(sometimes called neutralisers as they
prevent undesired movements) (e.g. the
brachialis acts as synergist when the
elbow is bent)
STABILISER – a muscle that stabilises the
origin of the prime mover (e.g. the deltoid
contracts (but does not move) to stabilise
the origin of the biceps)
FIXATOR – muscles that contract to keep
other joints of the body still
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Types of Contractions
Contraction = development of tension
within the muscle

Isotonic
• Concentric
• Eccentric
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
Isometric
Isokinetic
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Isotonic Contractions
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Involves movement
Contractions can be either concentric
(shortening) or eccentric
(lengthening)
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Concentric Contraction

A muscle actively
shortens and
thickens, creating
movement around
a joint (e.g. the
biceps
concentrically
contracts to allow
the elbow to bend)
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Eccentric Contraction
A muscle contracts but lengthens
 2 ends of the muscle are drawn apart
 Acts against gravity to control movement
(acts like a brake)
(e.g. the biceps that contracted
concentrically to curl the elbow will be
subject to an eccentric contraction to
control the lowering of the arm against the
force of gravity)

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Isometric Contraction
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A muscle contracts (develops tension) but
no movement occurs, therefore no change
in muscle length (e.g. curl the arm
upwards and then hold in that position, or
tug of war)
The tension in the muscle is exactly the
same as the opposing force
Fixator muscles often contract
isometrically
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Isokinetic Contraction
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
Muscle worked at maximum tension
throughout its range at a controlled
speed
Requires expensive specialised
equipment (often used for
rehabilitation)
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Student Practical
Worksheet 40 and 41

Work in pairs and carry out the following
exercises:
•
•
•
•
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Press ups
Sit ups
Arm wrestle
Ski squat
What muscles are being worked?
What type of contractions are taking
place?
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Learning Outcomes
By the end of this session you should
be able to:
 Explain the terms origin and
insertion
 Identify at least 4 different roles of
muscles
 Explain the terms isotonic,
concentric, eccentric, isometric and
isokinetic contraction
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