Unit 1: The Body in
Sport
2. Understanding the muscular
system and how it is affected
by exercise
In this section you will
learn how the skeletal and
muscular systems are
linked in the creation of
movement during sports
activities. You will also
learn about the structure
of joints and levers in the
production of movement.
Classification of muscles
• All sports performers need to be able
to move. Movement is possible
through the use of muscles, but not
all muscles bring about movement.
• There are three different types of
muscle tissue that make up the
muscular system.
• Can you name them?
The three different types of
muscle tissue are:
1. Cardiac muscle, which is only found in
the heart.
2. Smooth muscle, also known as
involuntary muscle.
3. Skeletal muscle, also known as voluntary
muscle
•
The structure and function of each of
these muscle tissues are very different,
and they are controlled by different
methods
Cardiac Muscle
• This type of muscle is only found in
the heart, and is a special form of
involuntary muscle in that we have
no direct conscious control over it. It
also differs from voluntary muscle in
that it does not tire, but continues to
contract and relax throughout our
lives.
Involuntary or Smooth
Muscle
• Examples of this type of muscle can
be found in parts of the digestive
tract propelling food through the
digestive system and the blood
vessels that aid blood flow away
from the heart to all parts of the
body.
Skeletal or Voluntary Muscle
• This type of muscle is attached to
the skeleton of the human body and
is responsible for bringing about
movement and maintaining body
posture. These muscles are
controlled by the central nervous
system and we move these muscles
with conscious thought.
Your body has over 600 muscles to
enable it to move.
You are going to concentrate on just 11. Can you
name any muscles?
•
•
•
•
•
•
Hamstrings
Quadriceps
Triceps
Deltoid
Latissimus dorsi
Gastrocnemius
• Bicep
• Pectoral
• Gluteus maximus /
Gluteals
• Trapezius
• Abdominals
Anterior View of the
muscular system
Posterior view of the
muscular system
Muscle and Sporting action
Triceps - Extends lower arm at the elbow
Volleyball player has arms outstretched to block the
ball
Biceps - Flexes arm at the elbow
Tennis serve – racket preparation, when racket is
behind head
Deltoids - Abducts upper arm at the shoulder
Preparation for a cartwheel in gymnastics
Pectorals - Adduction of upper arm at the shoulder
Arm action in front crawl (pull)
Trapezius - Adducts and rotate scapula, rotation of
head at atlas and axis
Lifting of the head to watch the flight of the shuttle
in badminton
Muscle and Sporting action
Gluteals - Extends the leg at the hip
Running action, one leg is left stretched back
behind the other
Quadriceps - Extends the leg at the knee
Follow through after kicking a ball in football
Hamstrings - Flexes the leg at the knee
Taking the leg back in preparation to strike the ball
in rugby
Gastrocnemius - Plantar flexion of the foot
Going up onto toes prior to take off in a diving
competition
Latissimus dorsi - Adducts and rotates the
humerus at the shoulder
Pulling the arm back in archery
Abdominals - Flexes and rotates the trunk
Forward action in sit ups
Structure and function of skeletal
muscle
Skeletal muscles are
made up of many
thousands of fibres.
These in turn are
made of even
smaller fibres called
myofibrils. It is
within these smallest
fibres that the
contraction of the
muscle takes place.
Muscle movement
• Skeletal muscle has a vast supply of
nerve and blood vessels. Skeletal
muscle is also termed voluntary
muscle because movement is created
via conscious thought process.
Muscles pull to produce movement.
In other words, the cells of the
muscle tissue contract and then relax
to their original size.
How Muscles Work:
When you move a
part of your body
your muscles will
either:
• CONTRACT –
Bulge (get fatter)
and shorten
Or:
• RELAX – Return to
their original
length
Muscle Contraction
• Muscles work (contract and shorten) when
stimulated (told to do so) by the central nervous
system (CNS). The brain sends messages via the
spinal cord to the muscles it wishes to move. The
spinal cord acts like a telephone wire.
• Muscular tissue has the ability to contract
(shorten and bulge) and then return to its
original length because it has ELASTICITY.
• Voluntary / Skeletal muscles usually works across
a joint. They are attached to both bones by
strong cords called Tendons.
• Tendons are white, flexible, very strong and are
different shapes depending upon the muscle.
• In other words Tendons are the cords that
connect Muscles to Bone so a muscle has
tendons at both ends.
Antagonistic Pairs
Muscles work in pairs to provide movement for
physical activity, for example the biceps and triceps
work together to create movement.
Antagonistic pairs
Prime movers – these
muscles determine the
movement of an action via
contraction. For example
during the bicep curl, the
prime mover during the
flexion phase is the bicep.
Antagonistic – this muscle
works together with the
prime mover but creates an
opposition action. Using the
example of the bicep curl
again, during the flexion
phase the triceps enable the
arm to bend at the elbow
joint for the bar to move
towards the shoulder girdle.
Antagonistic pairs
During the downward phase
of the bicep curl the opposite
occurs. For example the
prime mover (Agonist) is the
triceps and the antagonistic
muscle is the bicep.
Origins and Insertion
Muscles PULL on Bones – muscles are
attached to two different bones with
tendons.
To make a joint move – one of these
bones will move but not the other
• ORIGIN –attached to the STATIONARY
bone
• INSERTION – attached to the MOVING
bone
Origins and insertion
Muscle Contraction
Muscles contract to produce movement. There are
three main types of muscle contraction: two where
obvious movement occurs and one where no
obvious movement is visible.
• Isometric contraction is where the
muscle stays the same length during
contraction, or when the activity is being
carried out. Tension occurs in the muscle
but the distance between the ends stay
the same
Muscle Contraction
• Isotonic concentric contraction is
when the muscle shortens when
performing an action. There is obvious
movement when the ends of the muscle
move closer together.
• Isotonic eccentric contraction occurs
when the muscles lengthen under tension.
The ends of the muscle move further away
during an action.