PDHPE
Nicole Goh
Preliminary Core 2: The Body in Motion
How do the musculoskeletal and cardiorespiratory systems of the body
influence and respond to movement?
Skeletal System
MAJOR BONES INVOLVED IN MOVEMENT
Bones have five main functions including:
 Support for the body, giving it shape, form and posture
 Protection of vital organs and soft tissue
 Assistance in body movement: Provide the attachment for muscles and serve as levers
 Manufacture of blood cells in the marrow cavities
 Provision of a storehouse for essential minerals such as calcium and phosphorus
Important Terms
 Long and short bones: Function has levers or to
transfer forces
 Flat bones: Provide protection for organs
 Cartilage: Prevents jarring and allows bones to
move freely on each other
Anatomical Terms
 Superior  Towards the head
 Inferior  Towards the feet
 Anterior  Towards the front
 Posterior  Towards the back
 Medial  Towards the midline of the body
 Lateral  Towards the side of the body
 Proximal  Towards the body’s mass
 Distal  Away from the body’s mass
STRUCTURE AND FUNCTION OF SYNOVIAL JOINTS
 Fibrous Joint  Immovable joint where no movement is possible
Eg. Bones of the cranium
 Cartilaginous Joint  Slightly moveable that permits limited movement
Eg. In the vertebral column
 Synovial Joint  Freely moveable that allows maximum movement
Eg. Hip joint
Ligaments
 Fibrous bands that connect the articulating bones

 Maintain stability in the joint by restricting excessive movement
 Tendons  Tough, elastic cords of tissue  Attach muscle to bone
 Synovial Fluid  Act as a lubricant, keeping joints well oiled and moving surfaces apart
 Forms a fluid cushion between two joint surfaces
 Provides nutrition for the cartilage and carries away waste products
1. Describe the function of the main structures of a synovial joint. (4 Marks)
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Nicole Goh
A synovial joint is one that is freely movable and thus allows maximum movement. It consists of
ligaments, tendons and synovial fluid. An example of this is the hip joint, which contains ligaments,
tendons, synovial fluid and cartilage. First of all, ligaments are fibrous bands that connect articulating
bones and help to maintain stability in the joint by restricting excessive movement. Furthermore, the
tendons are tough, elastic cords that attach muscle to bone to allow movement of the skeletal
system. The synovial fluid acts as a lubricant between the joint, hence acts as a fluid cushion
between the two joint surfaces. Finally, cartilage covers the surface of bones to further allow bones
to move freely over each other and hence produce maximum movement.
2. Explain how synovial joints allow human movement. (4 Marks)
A synovial joint is one that is freely movable and thus allows maximum movement. Examples of
synovial joints include the knee and elbow joints. Within a synovial joint, ligaments connect
articulating bones and help to maintain stability in the joint during movement by restricting
excessive movement while tendons attach muscle to bone. For example, the elbow is a synovial joint
where the bicep and tricep muscles are attached to the radius, ulna and the scapula bone in the
shoulder via tendons. During flexion and extension, the tendons pull on the bones to produce
movement whilst ligaments between the humerus and ulna help to stabilise the joint during
movement.
JOINT ACTIONS (EG. EXTENSION AND FLEXION)
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Nicole Goh
Identify the location and type of major bones involved in movement
Eg. long bones articulate at hinge joints for flexion and extension
Ball and socket
Hinge
Flexion and extension
Abduction and adduction
Circumduction
Flexion and extension
Pivot
Rotation
Sliding
Slight sliding movements
Saddle
Flexion and extension
Abduction and adduction
Circumduction
Shoulder
Hips
Elbow
Knee
Fingers
Neck
Forearm
Vertebrate
Bones of the wrist
Thumb
Muscular System
MAJOR MUSCLES INVOLVED IN MOVEMENT
MUSCLE RELATIONSHIP (AGONIST, ANTAGONIST)
 Agonist  Muscle that causes the major action; one that contracts (eg. bicep during flexion)
 Antagonist  Muscle that relaxes and lengthens to allow agonist muscle to contract
That is, antagonist muscles cause an opposite action to that cause by the agonist (eg. triceps)
 Stabiliser  Fixator muscles that act at a joint to stabilise it
1. With reference to one of the following images, or muscle groups you have studied, describe
the relationship between agonist and antagonist muscles. (3 Marks)
To produce movement, agonist muscles contract to cause the major action
while antagonist muscles relax and lengthen to help control the action
being made. In the first image, image A portrays the extension of the
elbow and thus the triceps act as the agonist muscles and contract while
the biceps act as antagonist muscles to relax and lengthen. In image B,
during flexion of the elbow, the biceps act as antagonist muscles while the
triceps act as antagonist muscles.
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Nicole Goh
TYPE OF MUSCLE CONTRACTION (CONCENTRIC, ECCENTRIC, ISOMETRIC)
 Isotonic (AKA Dynamic): Length of the muscle will change, becoming longer or shorter
- Concentric  Muscles shorten to cause movement at the joint
- Eccentric  Muscle lengthens while under tension; often happens with assistance of gravity
 Isometric  Muscle fibres activate and develop force but muscle length does not change
1. Describe how the skeletal and muscular body systems work together to enable movement.
(3 Marks)
The skeletal system relies on synovial joints to allow movement of the bones. The muscular system
works together with the skeletal system in order to produce movement. This is done by muscles,
which are attached to bones and the muscles pull on the bones, resulting in movement. The muscles
that pull on bones to produce a contraction movement are called agonist muscles whilst antagonist
muscles relax and lengthen to produce an extension movement. For example, during flexion of the
elbow, the biceps act as agonist muscles to contract and triceps act as antagonist muscles to relax.
Respiratory System
STRUCTURE AND FUNCTION
1. Nasal
4.Passages
Bronchi
- Hair- traps
dust,
which
is
Air passageways sneezed out
- Air is
warmed
filtered
provide
- Sends
air and
to alveoli
viatobronchioles
optimum conditions for gaseous exchange
5. Bronchioles
2. Pharynx
See “Bronchi”
- Conducting tube with-hairs
to filter
- Separates food and air
Alveoli
3. 6.
Trachea
- Smalltoairand
sacs
withthe
thin
walls
- Allows air to travel
from
lungs
- Close
to capillaries
- Lined with mucus
secreting
cells with hairs
Place
of
gaseous
that push foreign particles out ofexchange
the lungs
LUNG FUNCTION (INSPIRATION AND EXPIRATION)
Inspiration
 Diaphragm contracts and flattens
 External intercostal muscles lift ribs up and out
 This increases volume of chest cavity and decreases the air pressure in the lungs
 In response, air rushes into the lungs via the air passages
Expiration
 Diaphragm relaxes and moves up
 Internal intercostal muscles allow the ribs to return to its resting position
 Chest cavity decreases and so the air pressure inside lungs increases, hence it’s forced out
EXCHANGE OF GASES (INTERNAL, EXTERNAL)
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Nicole Goh




Air breathed in from the atmosphere contains 21% oxygen and 0.03% carbon dioxide
Pressure of oxygen is high in the alveoli and low in CO2
Blood in the capillaries are low in oxygen and high in CO2
This causes a pressure difference




Oxygen moves from air in alveoli across the alveolar-capillary wall into the capillary
Oxygen attached itself to haemoglobin in blood
CO2 unloads from the blood into the alveoli across the alveolar-capillary wall
This equalises the pressure of both oxygen and CO2
Analyse the various aspects of lung function through participation in a range of physical
activities
Effect of Physical Activity on the Respiratory System
 Respiratory system is responsible for circulating oxygen around the body and removing CO 2
 During PA, respiratory system increases available O2 to working muscles
 During pre-exercise phase, ventilation slightly increases as an anticipation for exercise
 When exercise beings, body requires increase of O2 and ventilation increases to respond to O2
needs and requirements of muscles at work
 Heart rate increases to increase supply of O2 to muscles
 After exercise (recovery period), ventilation falls rapidly as muscles have stopped working
 Muscles do not need as much O2
 But CO2 needs to be removed and so ventilation rates above rest are needed
Circulatory System
Three parts of the circulatory system:
1. Blood
2. Heart
3. Blood vessels
COMPONENTS OF BLOOD
Functions of Blood
 Transportation of oxygen and nutrients to the tissues
 Removal of carbon dioxide and wastes
 Protection of the body via the immune system (through clotting to prevent blood loss)
 Regulation of body’s temperature
Components of Blood
Plasma




Red Blood Cells




White Blood Cells


-
Contains 90% water
Also contains proteins, nutrients, hormones, salts and wastes
Transports these substances to nourish tissues so they can function
Controls body heat through sweating
Make up 45% of blood volume and 95% of blood cells
Contain iron and a protein called haemoglobin
Haemoglobin carries oxygen around the body
Made in bone marrow
Formed in bone marrow and lymph nodes
Protects the body from disease
Phagocytes: Engulf foreign material
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PDHPE
Platelets
Nicole Goh
- Lymphocytes: Product antibodies to fight disease
 Made in bone marrow
 Produce clotting substances
STRUCTURE AND FUNCTION OF THE HEART, ARTERIES, VEINS AND CAPILLARIES
Heart
Inferior Vena Cava
Superior Vena Cava
 Carries deoxygenated blood from lower half of the body
 Carries deoxygenated blood from upper part of the body
Pulmonary Artery











Pulmonary Vein
 Carried oxygenated blood from lungs to left atrium’
Aorta
Right Atrium
Left Atrium
Right Ventricle
Left Ventricle
Largest blood vessel in the body
Carries oxygenated blood from heart to every cell of the body
Accepts deoxygenated blood from major veins
Pumps collected blood to the right ventricle through the tricuspid valve
Receives oxygenated blood from lungs through pulmonary veins
Oxygenated blood passes through bicuspid valve to left ventricle
Receives deoxygenated blood from right atrium
Pumps it into the pulmonary artery to be carried to the lung
Received oxygenated blood from the left atrium
Pumps it into the aorta
Carries oxygenated blood from right ventricle to lungs
Note: Atrioventricular valves prevent backflow during systole (heart contracts to pump blood)
During diastole (heart relaxes and fills), they open to allow blood to flow to the ventricles
Arteries
 Have thick, strong elastic walls containing smooth muscles to withstand pressure of blood forced
through them
 Carry blood away from the heart
 Eventually branch off into arterioles and then into capillaries
Veins
 Have thin walls as blood pressure is low
 Valves in veins prevent backflow of blood during periods when blood pressure changes
 Carry deoxygenated blood back into the right atrium
 Pulmonary veins carry oxygenated blood from lungs to the left atrium
Capillaries
 Smallest of all blood vessels; link between arterioles and veins
 Walls are extremely thin to allow for exchange of substances
 Function: Exchange oxygen and nutrients for waste
PULMONARY AND SYSTEMATIC CIRCULATION
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Nicole Goh
Pulmonary Circulation
 Flow of blood from the heart to the lungs and back to the heart
Systematic Circulation
 Flow of blood from the heart to the body and back to the heart
BLOOD PRESSURE
 Blood pressure is determined by:
- Cardiac output: Increase in cardiac output = Increase in blood pressure
- Volume of blood in circulation: If blood volume increases due to increase water retention (eg.
high salt intake), then blood pressure increases
- Resistance to blood flow: Increased viscosity of blood results in greater resistance and thus,
elevated blood pressure
 Systolic pressure: Highest pressure recorded when blood is forced into the arteries during
contraction of the left ventricle
 Diastolic pressure: Lowest pressure recorded when the heart is relaxing and filling
 Blood vessels (eg. aorta) pump blood around the body and so experienced pressure against their
walls; aorta has the highest blood pressure
 Veins are returning blood back into the right atrium and so have comparably lower pressure
 Veins rely on muscle contraction to act as a pump
Analyse the movement of blood through the body and the influence of the circulatory and
respiratory systems on movement efficiency and performance
Movement of blood through the body
 Deoxygenated blood from the body is emptied into the right atrium via the inferior and superior
vena cava
 Blood travels to the right ventricle through the tricuspid valve
 Pulmonary artery carries the deoxygenated blood to the lungs for oxygenation
 Pulmonary vein carries the oxygenated blood from the lungs to the left atrium
 Blood travels to the left ventricle through the bicuspid valve
 Oxygenated blood is pumped through the aorta to the rest of the body
Explain how lung respiration is affected by increasing physical activity
 Lung respiration includes inspiration and expiration
 During physical activity, the working muscles require more oxygen
 Hence inspiration and expiration increases in order to increase the intake of oxygen and the
removal of wastes such as carbon dioxide
 Heart rate also increases to pump oxygenated blood to the working muscles
 As physical activity increases, depth of breathing also increases in an attempt to maximise oxygen
intake and CO2 expiration
 Amount of physical activity a person normally undertakes also affects lung respiration
 More fit person will be able to efficiently exchange gases compared to a sedentary individual
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PDHPE
Nicole Goh
What is the relationship between physical fitness, training and movement
efficiency?
Health-related components of physical fitness
CARDIORESPIRATORY ENDURANCE – BEEP TEST




AKA aerobic power
Ability to working muscles to take up and use oxygen that has been breathed in during exercise
Provides the necessary nutrients and O2 to cells during exercise
Important in: Endurance events such as cycling and marathons
MUSCULAR STRENGTH – HAND DYNAMOMETER




Ability to exert force against a resistance in a single maximal effort
Sufficient strength enables efficient movement and reduces the incidence of injury
Hand dynamometer
Important in: Weight lifting, gymnastics and rugby
MUSCULAR ENDURANCE – SIT-UP TEST
 Ability of muscles to endure physical activity for extended periods of time without undue fatigue
 Without it, technique deteriorates and efficient movement is jeopardised and the likelihood of
injury increases
 Important in: Cycling, cross-country running and rowing
FLEXIBILITY – SIT AND REACH TEST
 Range of motion about a joint OR the ease of joint movement
 Helps to prevent soft tissue injury and improve blood circulation
 Can strengthen the muscle if combined with isometric exercises
BODY COMPOSITION – SKIN FOLD CALLIPERS OR BMI
 Percentage of fat as opposed to lean body mass in a person
 Excessive storage of fat places additional strain on joints
Analyse the relationship between physical fitness and movement efficiency. Students
should consider the question, “To what degree is fitness a predictor of performance?”
(Relate all points together – See textbook and workbook for sample answers)
Skill related components of physical fitness
POWER
 Ability to combine strength and speed in an explosive action
 Vertical jump test or standing long jump
SPEED
 Ability to perform body movements quickly
 50m sprint
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AGILITY
 Ability to move body from one position and direction to another with speed and precision
 Shuttle run
COORDINATION
 Ability to harmonise the messages from the senses with parts of the body to produce smooth
and well controlled movements
 Enables athletes to learn more skills quicker and perform acquired skills more consistently
 Also decreases chance of injury
 Juggling with one hand
BALANCE
 Ability to maintain equilibrium while either stationary or moving
 Poor balance can lead to falls, poor technique and inferior skill execution
 Stork stand
REACTION TIME
 Time taken to respond to a stimulus
 Slow reaction time leads to poor skill execution and increased risk of injury
 Ruler test
Think critically about the purpose and benefits of testing physical fitness
Outline advantages and disadvantages of fitness testing. (5 Marks)
ADVANTAGES
Fitness testing examines an individual’s ability of health-related and skill-related physical fitness
including muscular strength and endurance as well as coordination and agility. The benefits of fitness
testing are that it allows individuals to discover their strengths and weaknesses regarding their body
and hence act accordingly to ensure maximum movement efficient without the risk of injury. For
example, a rugby player would undertake the beep test to test their cardiorespiratory endurance
whilst a sit up test would help to determine their muscular endurance. As a result, they’ll be able to
monitor their progress and hence structure effective training programs to enhance their sport
performance.
DISADVANTAGES
While fitness testing are generally quick and easy methods at assessing one’s fitness in the various
areas, there are also some disadvantages associated with some of the tests . For example, the sit and
reach test is a quick and easy method of determining one’s flexibility. Generally, being able to touch
your toes is an average result. However, people with long arms in proportion to their legs may find
this task easier and so it can produce unreliable results as it’s not truly testing one’s flexibility.
Furthermore, the muscle strength test is using a hand dynamometer, which in turn provides a value
of forearm strength. However, some people have may stronger leg muscles due to running and thus,
this test does not cater for all types of strength. Finally, any fitness tests that involve the use of time
as measurement may not be an accurate representation of the person’s speed as reaction time,
another fitness component is a factor in play. If a person has slow reaction time but fast speed in a
sprint test, this may affect their results as they’ll achieve a slower time overall.
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Nicole Goh
Aerobic and anaerobic training
FITT PRINCIPLE
Frequency
 Must train at least 3 occasions a week, but can increase to 5
 Aim to stress the body systems and cause an adaptation
 Resistance training: 3 sessions are sufficient while 4 is maximal to allow rest days in between for
muscle fibre to regenerate
Intensity
 Amount of effort required to gain a fitness benefit
 Measuring intensity (aerobic activity): Use target heart rate zone as a guide
 Target HR zone: Area surrounding target HR; use percentages of MHR
 MHR – 220bpm subtract your age
 Poor fitness: Work at 50-70% of MHR
 Good fitness: Work at 70-85% of MHR
 Resistance training: Intensity is established by varying load, repetition, sets or the rest period
Time
 Good health: Last 20 to 30 minutes
 Can increase to 40 minutes
 60 minutes+ can lead to overtraining and possible development of overuse injuries
 None of these times include warming up and cooling down
 Duration: 6 weeks is the minimal period for realisation of a training effect
Type
 Best type is continuous exercise that use large muscle groups
Eg. Running, cycling, swimming and aerobics
 These activities draw heavily on our oxygen supply
 Hence increases breathing rate, heart rate and blood flow to the working muscles
 Aerobic fitness improves as cardiorespiratory system adapts
 Resistance training: Low resistance with high repetitions is preferable
 Can be provided using many activities such as circuit training and resistance bands
Design an aerobic training session based on the FITT principle
How is the FITT principle used to improve aerobic training? (4 Marks)
The FITT principle involves adjusting the frequency, intensity, time and type of exercise in
accordance to a person’s training program or need to improve particular fitness component such as
cardiorespiratory endurance. In order to improve aerobic training, an individual should train at least
3 times a week though this can be increased to 5 sessions. Training 3-5 times a week aims to stress
the body systems and as a result, cause an adaptation. Meanwhile, the intensity a person should
train at ranges from 50-85% of their maximal heart rate, depending on their current level of fitness;
person with poor fitness should work at about 50-75% of their MHR while those with good fitness
can extend it to 70-85% of their MHR. Furthermore, to improve aerobic training, sessions should last
between 20-30 minutes, though should not exceed 60 minutes as this can lead to overtraining.
Finally, the best type in this scenario should be continuous exercises that utilise the large muscle
groups including running and cycling. Since these activities draw heavily on our oxygen supply, it will
hence improve our cardiorespiratory system by causing it to adapt.
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PDHPE
Nicole Goh
Compare the relative importance of aerobic and anaerobic training for different sports
Eg. Gymnastics versus soccer
Compare the importance of aerobic AND anaerobic training in TWO different sports/physical
activities. (6 Marks)
Depending upon what type of exercise an individual undertakes and at what intensity they’re
working at will determine if it’s aerobic or anaerobic in nature. Typically, aerobic training includes
swimming and cross country running, where an individual works at approximately 70-85% of their
maximal heart rate (MHR) at a low to moderate intensity and lasts for approximately 30 minutes.
These exercises are aerobic as they utilise the large muscle groups such as our quadriceps and
hamstrings in running whilst our biceps and triceps are also used in swimming. Due to the use of
large muscle groups, these activities draw heavily upon our oxygen supply in order to supply the
working muscles with the oxygen needed to function. Since cross-country running also improves
muscular endurance of the hamstrings and quadriceps, anaerobic training in the form of resistance
training may prove to be useful in improving muscular strength and endurance. On the other hand,
resistance training of the forearm may be useful for swimming as it can provide more power with
each stroke, and thus provide more thrust to propel the swimmer forward.
Meanwhile, anaerobic training such as sprints and weight training work in the anaerobic threshold
above 85% of an individual’s MHR. The main difference between anaerobic and aerobic training is
that anaerobic involves high intensity with repetitions but in a shorter time span as it focuses on
working with the absence of oxygen. As a result, circuit training with 2-minute exercises and short
intervals in between are useful for anaerobic training, as anything more than 2-minutes may turn
into aerobic training. This type of training is typically used by athletes to promote strength, speed
and power while body builders perform weight training to build muscle mass. In these scenarios,
aerobic training does not have an impact on the performance of an individual who aims to improve
the stated fitness components and thus, does not play a part at all during anaerobic exercise.
Overall, depending upon the type of sport or physical activity an individual participates in will
determine if they should undergo aerobic or anaerobic training to enhance their performance. That
is, aerobic training focuses on cardiorespiratory and muscular endurance while anaerobic training
mainly improves muscular strength, speed and power.
Complete the following table to illustrate some differences between aerobic and anaerobic
training. (3 Marks)
Training Intensity
Type of activity
Targeted fitness
components
Aerobic
Low to moderate intensity
Continuous exercise that utilise
the large muscle groups
eg. running, cycling and
swimming
Cardiorespiratory endurance
Anaerobic
High intensity
Large number of repetitions with low
weights
Eg. Lifting dumbbells, resistance
bands, circuit training
Muscular strength and power, agility
and muscular endurance
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Immediate physiological responses to training
Factor
Heart Rate
Ventilation Rate
(Depth and rate
of breathing –
breaths per
minute)
Stroke Volume
(Amount of
blood pumped
from the left
ventricle per
beat)
Cardiac Output
(Amount of
blood pumped
from the left
ventricle per
minute)
Lactate Levels
(Concentration
of lactic acid
present in the
blood, product
by breakdown of
carbs)
Immediate physiological
response
 Rises in anticipation of
exercise
 Linear increase until MHR
 Plateaus when steady
state is reached during
prolonged exercise
 Rises in anticipation of
exercise
 Second rise as rate and
depth of breathing
increases
 Rise corresponds with
increased oxygen
consumption and CO2
produced
 Increases due to need to
remove CO2 rather than
the need for oxygen
 Increases during exercise
 Greatest increase is from
period of rest to moderate
intensity
 Plateaus as exercise
intensity increases
Resistance Training
Recovery Period
 Increase in HR as
more repetitions
are performed
 The fitter you
are, the quicker
you recover
 Increase in
ventilation rates as
more repetitions
are performed
 Initial decline
followed by
gradual return to
normal states
 Virtually no change
from resting levels
 Sharp increase as exercise
commences
 Continues as workload
increases in order to
meeting exercising
muscles’ need for O2
 Concentration increases as exercise increases
 High intensity creates higher lactate levels
 Accumulates when we exercise above the lactate
inflection point
 High levels of lactate make it difficult for muscle
fibres to contract
 Once maximal
exercise ceases,
lactate levels will
begin to return
to resting levels
Examine the reasons for the changing patterns of respiration and heart rate during and
after submaximal physical activity
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PDHPE
Nicole Goh
How do biomechanical principles influence movement?
Biomechanics: Science concerned with forces and the effect of these forces on and within the
human body
 Choose the best technique to achieve our best performance with consideration to body shape
 Reduces the risk of injury by improving the way we move
 Design and use equipment that contributes to improve performances
Motion
THE APPLICATION OF LINEAR MOTION, VELOCITY, SPEED, ACCELERATION, MOMENTUM IN MOVEMENT AND
PERFORMANCE CONTEXTS
Motion: Movement of a body from one position to another
Linear motion: When the body and all parts connected to it travel the same distance in the same
direction and at the same speed
Eg. Skiing, swimming and sprint events
Angular motion: Motion of an object about a fixed point or fixed axis
Movements include: Rotating, spinning, swinging or rolling
Eg. Ballet, skateboarding and figure skating
Velocity: Displacement/Time
Displacement: Movement of a body from one location to another in a particular direction
Speed: Distance/Time
Acceleration: Rate at which velocity changes in a given amount of time
Positive acceleration: Increase in velocity
Negative acceleration: Decrease in velocity
Momentum: Quantity of motion that a body possesses
Momentum = Mass x Velocity
Linear Momentum: When moving bodies travel in a straight line
Angular Momentum: When moving bodies generate momentum that does not travel straight
Conservation of Momentum: Moment is always conserved in a close system
- Contraction and rebounds release heat and sound energy
- Also pushes the ball forward
Apply principles of motion to enhance performance through participation in practical
workshops
Example: 100m sprint
 Body position at the start promotes forward thrust and increases power by placing the centre of
gravity low in front of the torso
 Starting blocks allow legs to be in a more efficient position to deliver thrust
 Body position after crossing the line promotes deceleration with a backward lean in a upright
position. This causes the centre of gravity to return to within the body alignment
 Deceleration occurs with more heel strike long stride lengths
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Nicole Goh
Balance and stability
-
CENTRE OF GRAVITY
 Definition: Point at which all the weight is evenly distributed and about which the object is
balanced
 In the human body, position of centre of gravity depends on how body parts are arranged
 Varying the centre of gravity in the execution of a skill can enhance performance
 High jumping  Fosbury flop technique  Centre of gravity does need to clear the bar as it’s
outside of the body
 Scissor method  Jumper must propel their entire body over the bar as the centre of gravity
must clear the bar
-
LINE OF GRAVITY
 Definition: Imaginary vertical line passing through the centre of gravity; extends to the ground
 Indicates the direction that gravity is acting on the body
 Most stable: Line of gravity falls through the centre of the base of support
-
BASE OF SUPPORT
 Definition: Imaginary base that surrounds the outside edge of the body when it’s in contact with
a surface
 Narrow base: Small force is needed to make the person lose their balance
 Wide base: Essential for stability
 Closer the centre of gravity is to the base of support, the more stable the body is
 Together, they provide stability and explosive power to change directions quickly
Apply principles of balance and stability to enhance performance through participation in
practical workshops
Describe how balance and stability can be used to enhance performance. (4 Marks)
To enhance performance, an individual can manipulate their centre of gravity and hence the line of
gravity, as well as their base of support in order to best execute particular moves. For example,
tennis players often lower their centre of gravity by bending forward and widen their base of
support by standing with their feet apart in preparation to receive a fast serve. The wide base of
support enhances their balance and stability and also enabled the centre of gravity to be moved in
the desired direction more easily. Furthermore, the centre of gravity can be varied in the execution
of a skill in order to enhance performance. For example, normally, our centre of gravity is in the
middle of our body. Hence, a high jumper often employs the fosbury flop technique in contrast to
the scissor method as their centre of gravity does not need to clear the bar while in the scissor
method, the jumper must propel their entire body over the bar. As a result, balance and stability are
crucial factors to consider to enhance skills and performance in sporting events.
Describe how a gymnast applies the principles of balance and stability in performing a handstand.
(6 Marks)
The principles of balance and stability include the manipulation of the centre and line of gravity and
also a person’s base of support. The centre of gravity is defined as the point at which all the weight
of an individual is evenly distributed and about which the object is balanced while the line of gravity
is an imaginary line that falls that through the centre of gravity and extends to the ground. The base
of support is an imaginary base that surrounds the outside edge of the body when its contact with a
surface.
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PDHPE
Nicole Goh
First of all, a wider base of support provides more stability and thus, a gymnast should spread their
hands out further to maintain the handstand. Furthermore, gymnasts must have a high level of
control over their centre of gravity by tightening their stomach, shoulders and hips in order to keep
their body in a straight line. As a result, the line of gravity will fall directly through the centre of the
gymnast’s body and thus fall directly in the centre of the base of support. This maximises stability
and enables the gymnast to hold the handstand without falling over.
If the gymnast arches due to the position of their legs, such as the legs arching past their head, it will
cause the centre of gravity to shift outside of the body, leading to a loss of balance. This is also due
to the action of gravity acting on the legs so it will pull the gymnast’s body down towards the
ground. Therefore, this shows the importance of maintaining the centre of gravity within the body
by widening the base of support.
Fluid mechanics
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FLOTATION, CENTRE OF BUOYANCY
 Float: Buoyant force is greater than or equal to your weight
 Buoyancy: Upward force on the body experienced when immersed in water
 Centre of buoyancy: Point where the amount of volume under the water is equally distributed on
either side
 Keeping as much of your body under water as possible will maximise the amount of water
displaced; increases buoyant force and makes it easier to float
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FLUID RESISTANCE
 Drag: Force generated by an object when it travels through a fluid medium
 Lift: Force generated by an object moving through fluid that is in opposition to the gravitational
pull or weight of the object
 To improve resistance, make their bodies as smooth as possible
Eg. Close-fitting swimwear or shaving the body and head
 Effective kick in freestyle helps to keep the body streamlined and reduce drag
Apply principles of fluid mechanics to enhance performance through participation in
practical workshops
Outline how the dimpled design of golf ball surfaces allows greater distance to be achieved than by
striking a smooth ball
 Dimpled design enables it to trap ait at high velocities and thus create a smoother surface
 This reduces drag by redirecting more air pressure behind the golf ball rather than in front
 This higher pressure at the back forces them to go a longer distance
 Smooth balls do not allow this manipulation of pressure and thus do not go as far
Magnus Effect
 Refers to the effect of rotation or spin on objects in motion
 The effect explains why spinning objects (eg. golf balls) deviate from their normal flight paths
 Topspin: Occurs when a ball or object rotates forward on its horizontal axis
This causes it to drop sharply
 Backspin: Occurs when a ball or object rotates backward
This causes it to fall slowly at the end of flight
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PDHPE
Nicole Goh
Describe how principles of fluid mechanics have influenced changes in movement and
performance (eg. technique modification, clothing/suits, equipment/apparatus)
Explain how improved techniques and materials have been employed to reduce both profile and
surface drag in sporting activities
 Specially designed suits and swimwear in swimming activities have helped to reduce both profile
and surface drag; the suits are usually extremely tight, reducing cross-sectional size
 The suits can also entrap fluid in its surface and thereby reduce friction by producing a water-onwater effect on drag
 Streamlined body position; avoid entering head too early, which increases drag
 Arm stroke is curvilinear to allow pushing back on still water and this provides more thrust
 Cyclists also minimise cross-sectional size by tightly crouching and using specialised handle bars
to produce a shape that minimises drag
 Bikes will less spokes also minimise drag
1. Discuss how knowledge of the principles of fluid mechanics has influenced changes in
movement and performance. (5 Marks)
Understanding fluid mechanics including fluid resistance, flotation and the centre of buoyancy have
led to the introduction of various movements, techniques and equipment in order to enhance
performance.
For example, swimmers often wear specially designed swimwear including swimming caps to help
reduce profile and surface drag. Since the swimwear is extremely tight and conforms to the
swimmer’s body shape, this also helps to reduce cross-sectional size. Special suits in professional
swimming can also entrap fluid in its surface and hence reduce friction and fluid resistance by
producing a water-on-water effect on drag. Furthermore, understanding the principles of flotation
and how the centre of buoyancy can be affected has led to the improvement of swimming
techniques. For example, flotation arises when the buoyant force acting on the swimmer is greater
than or equal to their weight. Hence, keeping as much of their body under water as possible during
backstroke will increase the buoyant force, thus making it easier to float.
Furthermore, the Magnus effect is a form of fluid resistance that comes into play in ball sports such
as golf, tennis and cricket. This concept refers to the effect of rotation or spin on objects in motion
and also helps to explain why spinning objects such as a cricket ball deviate from their normal paths.
In the context of cricket, the cricket ball has both a shiny and a rough side, thus allow for the
manipulation of air pressure to cause the ball to spin a particular way and deceive the opponent.
When the ball is bowled, the rougher side experiences low pressure and high resistance. As a result,
the ball will favour the low pressure and move in that direction. Through the understanding of fluid
mechanics, sportsmen such as cricket bowlers have been able to enhance their skills and
performance.
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PDHPE
Nicole Goh
Force
Force: Push or pull acting on an object
Force = Mass x Acceleration
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HOW THE BODY APPLIES FORCE
 Body produces force primarily through the muscular system promoting movement of the skeletal
system
 Body is faced with opposing forces such as gravity, air resistance, water resistance and friction
 Internal Force: Ones that develop within the body (eg. contraction of quadriceps when kicking)
 External Force: Comes from outside the body (eg. gravity)
 Applied Force: Generated by muscles working on joints
 Reaction Force: Equal and opposite forces exerted in response to applied forces
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HOW THE BODY ABSORBS FORCE
 Force distributed over a large area has less impact than that applied to a smaller area
 Changing the impact from direct to oblique will lessen the force
 Joints bend or flex in response to the impact generated by the force
- This helps to prevent injury to surrounding tissue
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APPLYING FORCE TO AN OBJECT
Greater the force applied, the greater the speed and acceleration of that object
Objects of greater mass require more force to move them than objects of smaller mass
Centripetal force: Directed towards the centre of a rotating body
Centrifugal force: Directed away from the centre of a rotating body
Apply principles of force to enhance performance through participation in practical
workshops
1. In the context of a team game, describe how the body applies and absorbs force. (6 Marks)
Force itself is a push or pull acting on an object and a body primarily does this through the muscular
system promoting movement of the skeletal system. In a game of cricket, there are three players to
consider: the bowler, the batter and the fielders.
According to Newton’s second law, force equals to mass times acceleration. Therefore, angular
momentum generated by the run-up and the overarm action of the bowl results in greater
acceleration of the ball. A consequence of this is a greater application of force to the cricket ball. This
same idea can be applied to the batter as well. That is, as the batter swings his bat, he applies force
through the momentum of the swing in order to hit the ball over a large distance.
Furthermore, the absorption of force is most evident in the fielders including the wicket keeper, as
they catch the accelerating ball. Following Newton’s first law of motion, the cricket ball will continue
to remain in motion until an external force is applied to it. When a fielder catches a ball, they apply
force to it in order to prevent it from staying in motion and the absorption of the remaining force
due to the acceleration of the ball is done through flexion of the elbow and a carry through to the
waist and thus, prevents injury of the hand. Furthermore, cricket pads will also absorb force by
distributing the force over the area of the pad.
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