Muscles
Your body has over
600 muscles to
enable it to move.
There are 3 types of
muscle:
1. Heart (cardiac)
muscle, which is
only found in the
heart.
2. Involuntary
(smooth) muscle,
found in places
like your iris,
intestines,
oesophagus.
3. Voluntary
(skeletal) muscle,
any muscle that
you can
consciously
control.
(External oblique)
Hamstrings
Quadriceps
Cardiac / Heart muscle
Cardiac muscle has a built in ‘pacemaker’, known as the sino-atrial
node, that controls the rate of the heartbeat. The rate of
heartbeat is an involuntary action but can be influenced by factors
such as stress, medication, illness and exercise.
These factors change the amount of hormones which are
released, which result in a change of heart rate.
Involuntary (smooth) Muscle
Found in organs, digestive system and blood
vessels, these muscles are completely controlled
by the autonomic nervous system (spinal cord).
Called smooth muscle due to its smooth
appearance under a microscope.
Voluntary (skeletal) Muscle
This type of muscle is attached to the skeleton
and provides movement and stability. It is also
called striated muscle because of its stripey
appearance under a microscope. The muscles
are controlled by the central nervous system
(brain), therefore it requires conscious thought
for movement to occur.
Muscle Type
Muscle Structure
Primary Function
Control
Mechanism
Location
Cardiac Muscle
A combination of
striated and
smooth muscle
tissue
Allows pumping
action of the
heart, during rest
and exercise
The heart’s
automatic
nervous system
assisted by the
autonomic
nervous system
(ANS)
Heart
Involuntary
Muscle
Smooth
Maintains the
different functions
of many vital
organs of the
body
Controlled
Blood vessels,
without conscious organs
thought.
ANS
Skeletal Muscle
Striated or striped To provide
movement of the
body
Central Nervous
system (CNS)
with conscious
thought.
Attached to
bones
Muscle Movement
• A tendon is a tough but flexible tissue that connects muscle to bone.
It is skeletal muscle that is responsible for movement during sporting
activity.
• Muscle can only pull, therefore, during muscular contraction, muscles
pull on bone to cause movement.
•To cause movement, muscle tissue contracts. The cells of the muscle
use chemical energy to work. This energy is created from the foods we
eat. Carbohydrate foods are the main fuel provider for muscle
contraction.
Antagonostic Pairs
Muscles work in pairs to provide movement for
physical activity.
• Prime
mover (agonistic) – This muscle determines the
movement of an action via contraction. For example, during a
bicep curl, the prime mover during the flexion phase is the biceps.
• Antagonistic – This muscle works together with the prime
mover but creates an opposite action. For example during the
bicep curl, during the flexion phase the triceps enables the arm to
bend at the elbow joint for the bar to move to the shoulder girdle.
Bicep curl flexion
Prime Mover
(shortens)
Antagonist
(lengthens)
Muscle Contractions
There are 3 main types of muscle contraction occurs. Two where
obvious movement occurs and one where there is no obvious
movement visible.
Isometric contraction is where the muscle stays the same length
during contraction, or when activity is being carried out. Tension
occurs in the muscle but the distance between the ends stays the
same.
Isotonic Concentric contraction is where the muscle shortens
when performing an action. There is obvious movement when the
ends of the muscle move closer together.
Isotonic Eccentric contraction is occurs when the muscles
lengthen under tension. The ends of the muscle moves further
away during an action.
Phase of Play
Muscle Group
Prime mover
Contraction
The lock after the scrum
has engaged
Quadriceps
Hamstrings
Gastrocnemius
Quadriceps
Isometric
The arms after the ball
has been thrown in from
a lineout
Triceps
Biceps
Triceps
Isotonic concentric
contraction
Isotonic eccentric
contraction
The draw back of the
leg as it prepares to kick
the ball.
Hamstrings
Quadriceps
Hamstrings
Isotonic concentric
contraction
Isotonic eccentric
contraction
Effects of Exercise on the Muscular System
Short Term
• An increase in blood flow to the exercising muscles, due to the increased demand of
oxygen by these muscles.
• An increase in the demand of fuel by the working muscles to complete the activity.
• An increase in the waste products that are produced by the working muscles resulting in
the demand for these waste products (e.g carbon dioxide, lactic acid) to be removed by the
body muscles.
• An increase in body temperature due to the muscles working harder to provide
movement.
Long Term
• Muscles become bigger and stronger depending on the type of exercise you
undertake. It takes up to six weeks for changes to the body to be seen.
However, it only takes two weeks for these changes to be lost if exercise does
not continue.
The increase in size of muscles through exercise is called
‘hypertrophy’