GCSE PE. YR10.
UNIT C5.
MUSCLES AND MUSCLE ACTION.
1. 3 TYPES OF MUSCLE.
1. VOLUNTARY MUSCLE e.g. biceps, triceps.
Also called SKELETAL MUSCLE.
We can actively control these muscles.
They are attached to the skeleton and cause movement.
2. INVOLUNTARY MUSCLE -
These are also called SMOOTH MUSCLE.
We cannot control these muscles.
They are found in internal organs such as the digestive and
circulatory systems.
They contract and relax automatically.
3. CARDIAC MUSCLE -
This is also INVOLUNTARY MUSCLE.
We cannot control this muscle.
The walls of the HEART are the only example of it.
The heart contracts rhythmically and continuously without tiring
for the whole of our life.
2. DIAGRAM OF THE MUSCULAR SYSTEM.
World of Sport Examined Teacher Resource Pack. Page 11.
3. FUNCTION OF MUSCLES.
See separate FUNCTIONS OF MUSCLES resource sheet.
Pupils use textbook to complete table.
4. MUSCLE FIBRES.
Muscles are made up of many muscle cells or fibres. Muscles contract (shorten) because these fibres
do. More fibres will be needed to contract for larger forces. There are two types of muscle fibre:
SLOW TWITCH FIBRES.
-
Contract slowly, without much force but can work for long periods under great stress.
They are deep red in colour.
They have a good oxygen supply which is necessary for creating energy.
Suited for endurance activities. E.g. long-distance running or swimming.
FAST TWITCH FIBRES.
-
Contract much quicker with much more force. They tire quickly.
They are white in colour.
Their oxygen supply is not as good.
They are suited for explosive events such as sprinting.
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Different muscles have different mixtures. Gastrocnemius has a lot of fast twitch fibres and so
standing on your toes is tiring.
Different people have different mixtures. Distance runners may have as much as 80% slow twitch
whereas some weight lifters may have 80 % fast twitch.
Each individual inherits their mixture from their parents. You cannot change it.
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5. MUSCLES AND MOVEMENT.
Skeletal muscles are responsible for all of our voluntary movement. They cause us to produce
complicated series of movements required for sporting actions. Muscles are attached to the skeleton
and pull on bones in order to cause movement across a joint. They cannot push.
Tendons attach muscles to bones at both ends.
The Origin is the where the tendon attaches the muscle to the end of the bone not moving.
The Insertion is where the tendon attaches the muscle to the end of the bone that moves.
E.g.
Elbow Joint -
Biceps
Triceps
Knee -
Quadriceps
Hamstrings
Origin = Scapula
Insertion = Radius
Origin = Humerus & Scapula
Insertion = Ulna
Origin = Pelvis & Femur
Insertion = Tibia
Origin = Pelvis & Femur
Insertion = Tibia & Fibula
ANTAGONISTIC PAIRS.
An antagonistic pair is two muscles which work together in order to move a limb. They must work
together as each can only pull to cause movement. Muscles cannot push.
Agonist - The muscle causing the prime movement.
Antagonist – The muscle which relaxes to allow the agonist to cause the prime movement.
E.g.
Elbow Joint -
Flexion Extension -
Knee Joint
Flexion Extension -
Agonist = Biceps.
Antagonist = Triceps.
Agonist = Triceps.
Antagonist = Biceps.
Agonist = Hamstring.
Antagonist = Quadriceps.
Agonist = Quadriceps.
Antagonist = Hamstring.
FLEXOR – Any muscle which pulls in order to flex or bend a joint.
EXTENSOR – Any muscle which pulls in order to extend or straighten a joint.
6. TYPES OF MUSCULAR CONTRACTION
There are different ways that muscles can contract. These come under two main categories:
1. ISOTONIC CONTRACTIONS.
These occur when the muscle contracts and changes in length.
e.g.
Dumb-bell curl. Biceps contracts (and shortens) in order to raise the dumb-bell. Triceps
relaxes. Biceps contracts (and lengthens) in order to lower the dumb-bell under control.
Triceps relaxes.
CONCENTRIC CONTRACTION.
When a muscle performs an ISOTONIC CONTRACTION and shortens. Dumb-bell UP.
ECCENTRIC CONTRACTION.
When a muscle performs an ISOTONIC CONTRACTION and lengthens. Dumb-bell DOWN.
2. ISOMETRIC CONTRACTIONS.
When a muscle contracts but stays the same length.
e.g.
During the dumb-bell curl, if the movement is stopped with the elbow at right angle, the bicep
is contracting but staying the same length.
Also:
Rugby scrum, tug of war, push hands together.
7. MUSCLE TONE AND POSTURE.
Muscle Tone – Our voluntary muscles are in a constant state of very slight tension even when stood
still ready and waiting to be used. This is called muscle tone. The closest muscles get to being totally
relaxed is during sleep. Poor muscle tone may lead to poor posture (see below). Exercise makes our
muscles stronger and thus our muscle tone better as we find it easier to maintain this contraction.
Posture – Posture is the way we hold our body when we are standing, sitting or walking. Good posture
has our whole body upright and well balanced. The position looks elegant and comfortable. If we are
not our weight becomes unevenly distributed and some muscles will have to carry extra weight. G
Possible causes of bad posture - Poor muscle tone, poor flexibility, weak muscles in lower back, legs
and abdominals, slouching over a desk for long periods, ill-fitting or high heeled shoes and being
overweight.
Improving posture – Exercise to improve muscle tone, muscular strength and flexibility. Awareness
and application of good posture habits.
Results of good posture – An individual who feels and looks good.
Posture when lifting – Use legs to lift weight – bend knees, keep back straight, keep weight close to
body.
FUNCTIONS OF MUSCLES.
For each of the following muscles, describe the movement(s) it causes and on which
joint. Also give an example of it’s use in a specific sport or a weight training exercise
used to strengthen it. Follow the example you have been given.
MUSCLE
MOVEMENT CAUSED
SPORTING EXAMPLE
BICEPS
Flexion at the elbow.
Biceps curl and chin-ups.
TRICEPS
DELTOID
TRAPEZIUS
LATISSIMUS DORSI
PECTORALS
ABDOMINALS
GLUTEALS
QUADRICEPS
HAMSTRINGS
GASTROCNEMIUS