The body in motion

How do musculoskeletal and cardiorespiratory systems influence and respond to movement?

Skeletal system

Terminology:

Anterior: Toward or on the front of the body: in front ofThe pectorals are on the anterior aspect of the bodyPosterior: Towards or on the back of the body: behindThe rhomboids are on the posterior aspect of the bodySuperior: Toward the head or upper part of a structure: aboveThe humerus is superior to the radiusInferior: Toward the lower part of a structure: belowThe tibia is inferior to the femurMedial: Toward or at the midline of the body: inner sideThe adductors are on medial to the abductorsLateral: Away from the midline of the body: outer sideThe abductors are on the lateral aspect of the legProximal: Closer to the origin of a point of referenceThe elbow is proximal to the wristDistal: Further from the origin or point of referenceThe foot is distal to the knee

Three planes of the body Sagittal – vertical plane which cuts the body into left and right Frontal or lateral plane - lies vertically however divides the body into anterior and

posterior parts. Transverse plane lies horizontally and divides the body into superior and inferior

parts.

Three planes of the body The sagittal axis passes horizontally from posterior to anterior and is formed by the

intersection of the sagittal and transverse planes. The frontal axis passes horizontally from left to right and is formed by the intersection

of the frontal and transverse planes. The vertical axis passes vertically from inferior to superior and is formed by the

intersection of the sagittal and frontal planes.

Skeletal system consists of 206 bones, joints between bones, cartilage and ligamentsProvides: framework, maintains posture, protects internal organs, produces red blood cells in bone marrow, provides and maintains calcium reserves for bone growth and repair, serves as levers for body movement.

Major bones in movement: Long bone: weight baring, protect against stress and act as levers

Short bones: as wide as they are long, primary function of providing support and stability with little movement

Flat bones: strong flat plates of bone with main function of providing protection for vital organs and a base for muscular attachment

Irregular bones: bones which do not fall into any other category in the body

Structure and function of synovial joints Freely moveable Connections between bones Have a cavity which contains synovial fluid which lubricates the joint. Ligaments are fibrous bands which help stabilise the joint.

Joint type Movement at joint Example StructureHinge Flexion/extension Knew/elbowPivot Rotation Top of neckBall and socket Flexion/extension,

adduction/abduction, internal and external rotation

Shoulder/hip

Saddle Flexion/extension, adduction/abduction, circumduction

CMC joint of thumb

Condyloid Flexion/extension, adduction/abductionCircumduction

Wrist/MCP

Gliding Gliding movements Intercarpal joints

Structure and function of synovial joints Articular capsule – capsule that encloses the joint cavity Articular cartilage – a connective tissue covering the surface of articulating bones Synovial fluid – a secretion that lubricates and nourishes the articular cartilage Tendons- fibrous cords of dense connective tissue that attaches muscle to bone Ligaments – dense connective tissue that attaches bone to bone.

Types of joints movements:

Flexion: Bending parts at a joint so that the angle between them decreases and the parts come closer together (bending the lower limb at the knee).

Extension: Straightening parts at a joint so that the angle between them increases and the parts move farther apart (straightening the lower limb at the knee).

Hyperextension: Excess extension of the parts at a joint, beyond the anatomical position (bending the head back beyond the upright position).

Dorsiflexion: Bending the foot at the ankle toward the shin (bending the foot upward).

Plantar flexion: Bending the foot at the ankle toward the sole (bending the foot downward).

Abduction: Moving a part away from the midline (lifting the upper limb horizontally to form a right angle with the side of the body).

Adduction: Moving a part toward the midline (returning the upper limb from the horizontal position to the side of the body).

Rotation: Moving a part around an axis (twisting the head from side to side). Medial rotation involves movement toward the midline, whereas lateral rotation involves movement in the opposite direction.

Circumduction: Moving a part so that its end follows a circular path (moving the finger in a circular motion without moving the hand).

Supination: Turning the hand so the palm is upward or facing anteriorly (in anatomical position).

Pronation: Turning the hand so the palm is downward or facing posteriorly (in anatomical position).

Eversion: Turning the foot so the sole faces laterally.

Inversion: Turning the foot so the sole faces medially.

Protraction: Moving a part forward (thrusting the chin forward).

Retraction: Moving a part backward (pulling the chin backward).

Elevation: Raising a part (shrugging the shoulders).

Depression: Lowering a part (dropping the shoulders).

Major Bones

Muscular System More than 600 muscles in the body Muscles are attached to bones and are called tendons The main of muscles is to contract Muscles shorten, causing joint movement, then relaxing as opposing muscles pull the

joint back into position

Three types of Muscles Skeletal muscles are primarily attached to bones and it moves the skeleton. It is

said to be striated. Contraction is under our direct control and so the movement of the muscles is said to be voluntary

Cardiac muscles form most of the heart. This is striated and involuntary Smooth muscles are located on the walls of our internal structures such as

stomach, blood vessels and intestines. Non striated and usually involuntary The muscles point of attachment it the more stationary bone is called the origin The insertion of muscles is the point of attachment at the moveable end. This

tends to be away from the bodies main mass The muscle action refers to movement made at the joint when the muscle

contracts

Muscle relation Most muscle of the musculoskeletal system work in pairs – agonist and antagonist The muscles that contracts or shortens is called the agonist The muscles that acts against or in the opposite direction to the agonist is called the

antagonist Antagonist moves body part back to original position Stabilisers or fixator muscles act as a joint to stabilise it, giving the muscles a fixed

base

Types of Muscle Contraction Concentric contraction – cause the muscle to shorten as it contracts. Example,

bending the elbow from straight to fully flexed, causing concentric contraction of the bicep

Eccentric – opposite of concentric and occur when muscle lengthens as it contracts. Example ; kicking a footy, the quads contract concentrically to straighten the knee and the hamstrings contract eccentrically to decelerate the motion of the lower limb

Isometric contractions – occur when there is no change in the length of the contraction muscle. For example ; this occurs when carrying an object in front of you as the weight of the object is pulling your arms down to your muscles are contraction to hold the object at the same height

The Respiratory System

Every cell in our body needs a constant supply of oxygen and food to maintain life and keep body operating effectively

The cardiorespiratory system is made up of cardiovascular and respiratory systems Provides us with oxygen and eliminates carbon dioxide and other waste through the

blood in a process known as respiration

Structure and Function Lungs are paired organs lying in the thoracic cavity Located either side of the heart, surrounded by strong connective tissue called pleural

membrane Each lung is divided by fissures into lobes. Left lung has 2 lobes, right lung has 3.

Right is thicker, broader and shorter than the left

Bronchi Right and left primary bronchi are formed from the branching of the trachea. In the

lung the primary bronchus in each lung branches into secondary and the tertiary bronchi

The process continues until the tiniest branches of the whole system are the air passages called the bronchioles, which are less than 1mm in diameter.

Alveoli Ends of the bronchioles (terminal bronchioles) feed into the pulmonary bronchioles

In the bronchioles are small sacs called alveola. They are covered in tiny capillaries. The exchange of gases occurs between the alveolar and capillary walls across a thin membrane.

Lung Function Breathing is the process by which air moves in and out. Controlled by the brain in two

phases; inspiration and expiration. During inspiration the diaphragm contracts and flattens. This increases the volume of

the chest cavity and pulls the walls of the lungs outwards, which in turn decreases air pressure in the lungs.

During expiration the diaphragm relaxes and moves upwards to allow the ribs and other structure to return to their resting position. The volume of the chest cavity is therefore decreased which increases air pressure. Air is consequently forced out to make the pressure inside and outside the lungs about equal.

Exchange of Gases Oxygen moves from the air in the alveoli across the alveolar- capillary wall into the

blood, where it attaches itself to haemoglobin in the red blood cells. At the same time, carbon dioxide is unloaded from the blood into the alveoli across

the alveolar-capillary wall to be breathed out.Gas Inhaled Air (%) Exhaled Air (%)

Oxygen20.93 16.4

Carbon dioxide

0.03 4.1

Nitrogen and other gases

79.04 79.5

The pressure of oxygen arriving at the alveoli is high and the pressure of it in the capillaries is low. Therefore oxygen diffuses from the alveoli into the blood. The opposite is true for carbon dioxide

How does the exchange of gases occur within our body? The exchange of gases occurs in the two stages of inspiration and expiration

During inspiration the diaphragm contracts and flattens. This expands the volume of the chest cavity and takes in oxygen. This oxygen then travels through the lungs, to the alveoli. The oxygen arriving at the alveoli is high in pressure. From the alveoli the oxygen diffuses into the blood via the alveolar-capillary wall into the blood where it attaches itself to the haemoglobin.

At the same time as this, the carbon dioxide from the blood travels through the alveolar-capillary wall into the lungs. This carbon dioxide is low in pressure. It is then breathed out through the process of expiration, which is where the diaphragm relaxes and moves upwards and returns the volume of the lungs to its starting position pushing out the carbon dioxide.

Effect of physical activity on respiration The rate and depth of breathing often increase moderately even before the exercise

begins Once exercise starts the rate and depth if breathing increase rapidly. This is due to

stimulation of sensory receptors in the body’s joints as a result of the movement The increases in the rate (frequency) and depth (tidal volume) of breathing provide

greater ventilation and occur, generally, in proportion to increases in the exercise effort.

A spirometer is a sophisticated testing of lung function that can be used to measure the following lung volumes

Vital capacity – the volume of air inspired in a normal breath after we have forcibly exhaled the air remaining in the lungs

Residual volume – the air that is still trapped in our lungs after we have forcibly exhaled

Total lung volume – the combination of vital capacity and residual volume

Circulatory System

Consists of heart, blood and other vessels Purpose: cardiovascular system delivers oxygen and nutrients to cells, removes waste

from cells and maintains the balance of water in the body

Components of Blood Blood accounts for 8% of our total body weight Healthy adult males have around 5-6 litres of blood in their bodies, while females

have around 4-5 litres of blood Its colour depends on the amount of oxygen. Deoxygenated is dark red. Oxygenated is

light red. Plasma makes us 55% of volume in blood (91.5% is water; the other 8.5% is made up

of nutrients, waste products, proteins, enzymes and hormones.) The other 45% is erythrocyte (red blood cells), leucocytes (white blood cells) and

platelets.

Plasma Much of the C02 and very small amounts of O2 are also carried in a dissolved state in

plasma Water(91.5%) is a significant component of the circulatory system and controls body

heat through sweat If sweating is extreme, excessive loss of water from plasma and tissues can decrease

blood volume, making frequent hydration necessary.

Erythrocytes (red blood cells) 99% of the formed elements is blood Contain an oxygen carrying pigment called haemoglobin, which gives blood its

colour Erythrocytes live for around 120days, and are replaced at around 2 million per

second Formed in the adult red bone marrow of some bones

White blood cells Exist in our bodies to combat infection and inflammation Formed in the bone marrow and lymph nodes Phagocytes, which engulf foreign material and harmful bacteria Lymphocytes, which produce antibodies to fight disease

Thrombocytes (platelets) Involved in the process of clotting, and help to repair slightly damaged blood vessels They have a life span of five to nine days

The Heart The heart is an involuntary muscle with striated muscle fibres

An adults heart weighs around 300 grams It is situated in the chest cavity in a space called the thoracic cavity, located between

the diaphragm , sternum and vertebral column Two-thirds of the mass of the mass lies to the left of the midsaggital line

Structure of the heart The superior chambers of the heart are called the left and right atrium The ventricles are quite large because they are responsible for propelling blood from

the heart into circulation around the body Dense connective tissue structure called valves prevent the back flow of blood into

chambers by opening and shutting when the heart contracts and relaxes

Arteries Carry blood away from the heart to tissues (red) They have thick elastic walls because blood is pumped through them at high pressure

in surges The arteries become smaller at the ends, further away from the heart

Veins Carry blood from tissues back to the heart (blue) The small vessels at the ends of veins are called venules The walls of veins are thinner and less elastic than artery walls, because the pressure

decreases as the blood gets closer to the heart Valves within veins prevents the blood from flowing back the wrong way against the

force of gravity

Capillaries Are very small networks of vessels through which nutrients are exchanged between

blood and the cells of the body They lie between arterioles and veins, connecting both systems Capillary walls are extremely thin consisting of a single layer of flattened cells.

These walls allow oxygen, nutrients, and hormones from the blood to pass easily through to the interstitial fluid, then into the cells of the body’s tissues

Cardiovascular system

Deoxygenated blood enters the right atrium via the superior and inferior vena cava It then pass through to the right ventricles From here it goes to the lungs via the left and right pulmonary arteries. In the lungs carbon dioxide is released and oxygen is picked up. This process is

known as pulmonary circulation Oxygenated blood then enters the left atrium via the pulmonary veins It then enters the left ventricle It travels to the rest of the body via the Aorta and goes to the upper and lower

extremities via a number of arteries. This is known as assystemic circulation

Fitness

Components of fitness Fitness means many things to many people Fitness is the ability to carry out everyday tasks without undue fatigue and to cope

with unforeseen situations (such as running to catch a bus) and having energy to enjoy leisure pursuits

Fitness is often equated with being healthy, but its meaning does not merely include physical well being

Health related components of Fitness The health-related components of physical fitness are all those aspects of fitness that

enable us to maintain our health, perform daily tasks and jobs, perform well in sporting activities and help protect us from sickness

They are the physical factors that, if we neglect them, may cause us to perform poorly and become unhealthy

Cardiovascular Fitness (Aerobic Fitness) This is also sometimes known as stamina and is the ability of your body to

continuously provide enough energy to sustain submaximal levels of exercise. To do this the circulatory and respiratory systems must work together efficiently to provide the working muscles with enough Oxygen to enable aerobic metabolism.

If we have good cardiovascular fitness then our health is also good as it helps with:o Fat metabolismo Improved delivery of Oxygeno Faster removal of waste productso Decreased levels of stress

Strength Strength is defined as the ability of a muscle to exert a force to overcome a resistance. Strength is important for our health as it enables us to :

o Avoid injurieso Maintain good postureo Remain independent (in older age)

Flexibility

Flexibility is the movement available at our joints, usually controlled by the length of our muscles. This is often thought to be less important than strength or cardiovascular fitness.

However, if we are not flexible our movement decreases and joints become stiff. Flexibility in sports allows us to perform certain skills more efficiently, and it is also important in other sports to aid performance and decrease the risk of injury.

In daily activities we must be flexible to reach for something in a cupboard, or off the floor. It also helps:

o Prevent injuries

o Improve postureo Reduce low back paino Maintain healthy jointso Improve balance during movement

Muscular Endurance

Muscular endurance, unlike strength, is the ability of a muscle to make repeated contractions over a period of time.

This is used in day-to-day life in activities such as climbing stairs, digging the garden and cleaning. Muscular endurance is also important in sports, such as football (repeated running and kicking), tennis (repeated swinging of the arm to hit the ball) and swimming (repeating the stroke).

Body Composition

Body composition is the amount of muscle, fat, bone, cartilage etc. that makes up our bodies. In terms of health, fat is the main point of interest and everything else is termed lean body tissue.

Excess body fat can contribute to developing a number of health problems such as heart disease and diabetes

Place strain on the joints, muscles and bones, increasing the risk of injury

Skill related components of fitness the skill related components of physical fitness are related to the performance aspect

of an activity they are the functional capacities that enable us to perform physical activities with

greater skill elite athletes will have very high levels of skill related fitness

Power muscular power can be defined as the ability to exert maximum force in the shortest

possible time combination of strength and speed

Speed the ability of the muscles to contract quickly this translates into fast movement of body parts speed is often determined by the individuals muscle fibres

Agility the ability to change direction or body positions quickly, while still maintain balance power, speed, balance, coordination and reaction time are components of agility

Coordination the result of the interaction between the body’s sense of perception and the Central

Nervous System

Good coordination makes movement appear smooth and flowing

Balance The body’s ability to maintain its equilibrium Equilibrium is lost when a person falls over or loses control of their body

momentarily Can be static or dynamic

Reaction time The time taken to respond to an external stimulus

Measuring health and skill related components of fitness The measurement of physical fitness usually involves the use of laboratory or field

tests to measure particular components No one test will measure all health and skill related components These results are then recorded and evaluated

Reasons to measure physical fitness Evaluate progress Make comparisons with others Develop accurate training programs Set realistic, achievable fitness goals Assess strengths and weaknesses Identify medical problems

Aerobic and AnaerobicAerobic = with oxygenAnaerobic = without oxygen

Aerobic training Aerobic exercise uses oxygen to help break down or metabolise energy sources to create

movement This type of exercise is performed at low to moderate intensity and at a steady pace and can

continue for an extended time, as long as there is fuel Exercises include jogging, swimming, walking Beneficial to cardio respiratory system

FITT PRINCIPLE Frequency = how often. 3-5 times a week Intensity = how hard. 60-85% Time = how long. 20 minutes Type = what sort of activity. Relevant to muscle groups and energy systems

Anaerobic training Involves a workload that is intense and short in duration This type of exercise relies on stored energy in the bod that can be metabolised in the

absence of oxygen Anaerobic exercise is short in duration time due to a limited supply of stored energy

and production of lactic acid which slows or impairs muscular contraction Many team sports rely on short intermittent bursts if anaerobic activity

To improve anaerobic fitness we need to:o Work hard at performing and enduring specific anaerobic movementso Practise the required movements at or close to competition speedo Use of activities such as interval training where periods of intense work at

interspersed with short burstso Utilise resistance training exercises to further develop the muscles required for

the movement

What is the relationship between physical fitness, training and movement efficiency?

Immediate physiological responses to training These are the changes that take place within specific body organs and tissue during

exercise

Heart Rate Is the number of times the heart beats per minute (BPM) A low resting heart rate is indicative of a very efficient cardiovascular system Our heart rate increases according to the intensity of our exercise effort Maximal heart rates are observed during exhaustive exercise In a fit person, heart rate levels off during protracted exercise reaching a steady state For an unfit person, heart rate continues to rise gradually as exercise is prolonged

Heart rate is therefore a good indicator of the intensity of exercise and may be used as a fundamental measure of a person’s cardiovascular fitness

Ventilation rate Refers to our depth and rate of breathing and is expressed in litres per minute When we begin to exercise the demand for more oxygen by the muscles cells causes a

ventilation response During rest, the ventilation rate is about 12 breathes per minute, causing the lungs to

consume around 500 millilitres of air per breath Once exercise starts, the rate and depth of breathing intensifies. This is matched by an

increase in oxygen consumption and carbon dioxide production, triggering elevated respiratory activity.

Stroke volume The amount of blood ejected by the left ventricle during a contraction. It is measure in

mL/beat When exercise increases, the amount of blood that the heart dischargers (per beat)

increases considerably Stroke volume is determine by

o The ability to fill the ventricles by blood volumeo The ability to empty the ventricles as a result of ventricular contractions

Stroke volume increases during exercise, with most of the increases being evident as the person progresses from rest to moderate exercise intensity

Why is there such a difference? This large increase is the availability of oxygenated blood to the working muscles explains their superior performance

It should be noted that the increase in stroke volume occurs as a result of more blood returning to the heart. This promotes a more forceful contraction.

Cardiac output Increases the same way as stroke volume It is a product of heart rate and stroke volume Cardiac Output (CO) = heart rate (HR) X stroke volume (SR) Cardiac output increases in response to physical demands being made on the body Output for both trained and untrained is approx. 5 litres, because elite athletes have a

lower heart rate

The immediate response to training indicates noteworthy differences between the two groups. While untrained people are able to increase cardiac output to around 20-22 litres per minute during exercise, highly trained endurance athletes can increases it to 35-40 litres per minute. This is achieved with a lower normal heart rate

During exercise 84% of the blood goes to the muscles because it needs the oxygen

Lactate Levels Lactate is a salt formed from lactic acid that accumulates during intense anaerobic

activity Lactate is a chemical formed during the breakdown of carbohydrates in the absence of

sufficient oxygen This lactate is continually resynthesised providing the body with energy Generally lactate flows freely in the blood and its concentration increases as the

workload is increased. High levels of lactate are produced when we exercise and there is insufficient oxygen

available to the muscle cells It accumulates rapidly when we exercise above the Lactate Inflection Point (LIP),

which occurs at about 80-90% MHR for trained athletes. This point is much lower for untrained athletes Lactate or lactic acid increases in the blood during exercise. If exercise is vigorous,

lactate increases rapidly and inhibits performance if levels rise to high

How do biochemical principles influence movement?

Motion – the application of liner motion, velocity, speed, acceleration, momentum in movement and performance contexts

Biomechanics A science concerned with forces and the effect of these forces on and within the

human body Is very important to understanding techniques in sport

It is of value to both coach and player because it is concerned with efficiency of movement

Motion Movement of a body from one position to another How motion is classified depends on the path followed by the moving object

Linear motion Takes place when a body and all parts connected to it travel the same distance in the

same direction and at the same speed Example – a person standing still on an escalator or in a lift The easiest way to determine if a body is experiencing linear motion is to draw a

straight line connecting two parts of the body for example, the neck and hips If the line remains in the same position when the body moves from one position to

another, the motion is linear Examples include swimming and sprint events where competitor race following a

straight line from start to finish.

Angular motion Angular momentum is shown in sports where bodies generate momentum, but they do

not travel in a straight line ; for exampleo Tennis serveo Football kicko Golf swing

In each of these cases, the body part of it, or an attachment to it such as a golf club or tennis raquet, is rotating

Angular motion is the quantity of angular motion in a body or part of a body When moving bodies do not travel in a straight line, it is called angular motion.

Velocity Velocity is equal to displacement divided by time Displacement is the movement of a body from one location to another in a particular

direction, or an ‘as the crow flies’ measurement Velocity is equal to displacement divided by time Velocity is used for calculation where the object does not move in a straight line An example is a runner in a cross country race.

Speed Speed is equal to the distance covered divided by the time taken to cover the distance Much of our potential for speed is genetic and relates to the type of muscles fibre in

our bodies However, individuals can develop their speed as a result of training and technique

improvements, the basis of which is the development of power and efficiency of movement.

Acceleration Acceleration is the rate at which velocity changes in a given amount of time When a person or object is stationary, the velocity is zero. An increase in velocity is

referred to as positive acceleration. A decrease is negative acceleration

The ability to accelerate depends largely on the speed of muscle contraction, but use of certain biomechanical techniques, such as forward body lean, can improve performance.

Momentum Refers to the quantity of motion that a body possess Product of mass and velocity. M= mV

Balance and stability

Centre of gravity The centre of gravity of an object is the point at which all weight is evenly distributed

and about which the object is balanced In the human body, the position of the centre of gravity depends upon how the body

parts are arranged, that is, the position of the arms and legs relative to the trunk

Base of support The amount of ground that supports you is your base of support When you stand up with your feet straight together, you have a small base of support Standing with your legs apart gives you a larger base of support Balance and stability improve with a larger base of support

Line of gravity The line of gravity is an imaginary vertical line passing through the centre of gravity

and extending to the ground The closer the line of gravity moves to the outer limits of the base of support, the less

stable we become.

Fluid mechanics Fluid mechanics is a branch of mechanics that is concerned with properties of gases

and liquids. For example cycling, snowboarding and swimming

Flotation To float is to maintain a stationary position on the surface of the water Buoyant force is the upward force on an object produced by the fluid in which is

fully or partially submerged The density of a boy or object refers to its mass per unit of volume Our body floats readily on water when the forces created by its weight are matched

equally or better by the buoyant force of the water For an object to float it needs to displace an amount of water that weights more than

itself If our weight density is high, that is we are relatively fat free, the body sinks in water.

Conversely if we have higher proportions of less compact tissue, such as fat, we tend to float.

The degree of density changes the buoyancy of an object or body Objects with densities higher than that of water (more mass) sink Object with densities lower than that of water (less mass) float It is common for people to sink non-uniformly from a horizontal stationary floating

position and this usually begins with the feet

The positioning of tissues such as the lungs, relative to the legs impacts on flotation and affects which parts sink first

What are the differences between moving on land and moving in air? Water and air environments are both fluid environments As our bodies move through these we are subject to various forces Immersed in water, there are two opposing forces actin on our bodies Gravity is a force pulling the body down Buoyant force is a force pushing up against a body When a body is wholly or partially submerged in a fluid, an upward buoyant force is

exerted on the body which is equal to the weight of the volume of fluid displaced Buoyant force > gravity = float. Buoyant force < gravity = sink The buoyant force and the force of gravity will remain constant. Density is the main

force acting on the body which includes bone structure, body fat.

Fresh bone = most dense. Muscle = next, similar to water. Fat = least dense People with a greater amount of body fat float better Legs sink first as they are denser and are mainly muscle and bone The lungs when full of air, act like a balloon Centre of gravity and buoyancy are generally located around the same place Centre of gravity is located around the navel Centre of buoyancy is located around the chest cavity

Fluid mechanics – fluid resistance Drag is the force that opposes the forward motion of a body or object, reducing its

speed or velocity Drag forces run parallel to flow direction (airflow , water), exerting a force on the

body in the direction of the stream The amount of drag experienced depends on a number of factors including

o Fluid density: because water is denser than air, forward motion in this is more difficult

o Shape: if a body or object is streamlined at the front, and tapered towards the tail, the fluid through which it is moving experiences less turbulence and this results in less resistance

o Surface: a smooth surface causes less turbulence, resulting in less drago Size of frontal area: if the front of a person or object (area making initial

contact with the fluid) is large, resistance to forward motion is increased

Much has been done to try to minimise resistance forces that oppose movement in fluid mediums

For exampleo Technique: cyclists, speed skaters and downhill skiers all bend forward at the

trunko Tactics: distance runners and cyclists follow one another closely where

possibleo Clothing: tight body suits made of special friction- reducing fabrics are won

by swimmers, cyclists and runners

o Equipment design: designs of equipment’s such as golf balls, golf clubs, cricket bats, bicycle helmets and surfboards are continually being modified to make them more aerodynamically efficient

The Magnus Effect Air effects flight of all projectiles When a ball spins there is a force perpendicular to the spin axis An outer layer of air sticks to the ball and rotates with it On the side of the ball that this outer layer collides with the air flowing past the ball, it

decelerates causing a high pressure area On the opposite side, the spinning ball moves in the same direction as the flowing past

it, which accelerates the ball creating a low pressure area As a result it curves in the direction of the low pressure area

Forces A force is something that causes or has the potential to cause, divert or slow the

movement of an object which it acts Force is measured in a unit called a Newton The muscles that contract to exert a force on the bones, cartilage and ligaments are an

example of internal force Any forces exerted outside the body (such as gravity, friction and air resistance) are

external forces The four common properties of forces are:

o Magnitude (an amount: how much is applied)o Direction (the angle at which the force is applied)o Point of application ( the specific point at which the force is applied to a body)o Line of action (represents a straight line through the point of application in the

direction that the force is acting)

Newtons Lawso First law: Every object in a state of uniform motion tends to remain in that state of

motion unless an external force is applied to it. Such as when a ball is rolledo Second law: The relationship between an object's mass m, its acceleration a, and the

applied force F is F = ma. Acceleration and force are vectors in this law. The direction of the force vector is the same as the direction of the acceleration vector. A golf ball being putted on a green

o Third law: For every action there is an equal and opposite reaction. Weights being lifted

Contact forcesThere are six types of contact forces:

o Athletes are in contact with the ground, and the reaction force that applies to the athlete is called the ground reaction force

o The force that two bones apply to each other across a joint is called the joint reaction force

o Friction is the force that resists the motion of one surface across anothero In many sports, motion is affected by the fluid in which it is performed. This is

called fluid resistance

o Force of inertia affects movemento When material changes its length when a force is applied to it, the force is said

to be an elastic force.

Summation of forces is the combined amount of forces action on the body or an objecto Summation of forces is affected by the:

o Number of body parts used in the movemento Order and timing of their involvemento Force and velocity generatedo Way in which body arts are stabilised for other body parts to act upon

Centripetal and centrifugal forceso When objects move along a curved path, a centre-seeking force acts towards the

centre of the rotation. It is called the centripetal force.o There is also an equal and opposite centre-fleeing force.

The momentum of the speeding body must be gradually decreased by joint actions, allowing forces to be absorbed

InertiaInertia is the property of matter by which it retains its state of rest or its velocity along a straight line so long as it is not acted upon by an external force.

Safety when collidingo There is a number of simple precautions to ensure safer collisions and impacts

between ourselves and other bodieso Use a large surface areao Keep as great a distance as possible between the impacting playerso Use as much mass as possible when landing or catchingo Regulate the position of one’s centre of gravityo Use materials other than body partso Protect projections of the body during impacto ‘give’ with the impact