edexcel a level physical education a 9536 next previous unit 6 a.1.1 edexcel examinations a level...

Unit 6 A.1.1

Edexcel A Level Physical Education A 9536

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Edexcel ExaminationsA Level Physical Education

A 9536

Unit 6 : Section Apart 1

Scientific Principles of Exercise and Performance

Unit 6 A.1.2


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INDEX19 - SKELETAL MUSCLE ANATOMY - STRUCTURE /

PHYSIOLOGY20 - SKELETAL MUSCLE ANATOMY - STRUCTURES SARCOPLASMIC RETICULUM / TROPOMYOSIN TROPONIN21 - STRUCTURE and PHYSIOLOGY of MUSCLE CELL

CONTRACTION STRUCTURE of a SARCOMERE / CONTRACTION22 - PHYSIOLOGY of MUSCLE CELL CONTRACTION EXCITATION and CONTRACTION23 - PHYSIOLOGY of MUSCLE CELL CONTRACTION

RELAXATION24 - STRENGTH OF MUSCLE CONTRACTION FACTORS AFFECTING25 - ATP - ADENOSINE TRIPHOSPHATE26 - ATP - RESYNTHESIS OF ATP27 - ATP / PC ALACTIC SYSTEM - THE PC SYSTEM28 - ATP / PC ALACTIC SYSTEM - THE PC SYSTEM THE COUPLED REACTION29 - ATP / PC ALACTIC SYSTEM - THE PC SYSTEM EFFECT OF TRAINING30 - THE LACTIC ACID SYSTEM - GLYCOLYSIS31 - THE LACTIC ACID SYSTEM - EVENTS / SPORTS

EFFECTS OF CONTINUED HIGH INTENSITY EXERCISE 32 - THE AEROBIC SYSTEM GLYCOLYSIS / KREB’S CYCLE (CITRIC ACID CYCLE) ELECTRON TRANSPORT CHAIN33 - THE AEROBIC SYSTEM34 - THE AEROBIC SYSTEM AEROBIC RESPIRATION / EXERCISE TYPES35 - THE ENERGY CONTINUUM36 - THE ENERGY CONTINUUM FACTORS AFFECTING PROPORTIONS OF ENERGY

SYSTEMSVARIATION IN CONTRIBUTION OF ENERGY SYSTEMS

Index

3 - ENERGY - DEFINITIONS4 - ENERGY CONCEPTS

APPLICATIONS / RATES OF ENERGY EXPENDITURE5 - INVESTIGATIONS

RUNNING UP STAIRS (Margaria Staircase Test)ENERGY VALUE OF FOOD EATEN

6 - ENERGY CONCEPTS7 - METABOLISM - ENERGY METABOLISM BASAL METABOLIC RATE (BMR) / TOTAL METABOLIC

RATE8 - MOTOR NEURONE STRUCTURE

CELL BODY / DENSRITES / AXON9 - TRANSMISSION OF NEURAL IMPULSE

AN ACTION POTENTIAL10 - TRANSMISSION OF NEURAL IMPULSE - CONDUCTION OF

ACTION POTENTIAL / MYELIN SHEATH11 - TRANSMISSION OF NEURAL IMPULSE

The MOTOR END PLATE / FUNCTION / ACTION12 - IMPULSE TRANSMISSION AT A NEUROMUSCULAR

JUNCTION13 - PRODUCTION OF COORDINATED MOVEMENT

MOTOR NEURAL FIRING PATTERNS / SINGLE FIBRE TWITCH WAVE SUMMATION

14 - PRODUCTION OF COORDINATED MOVEMENTMOTOR NEURAL FIRING PATTERNS / MULTIPLE FIBRE TWITCHES / SPATIAL SUMMATION

15 - PRODUCTION OF COORDINATED MOVEMENTMOTOR NEURAL FIRING PATTERNS / MULTIPLE FIBRE TWITCHES / GRADATION OF CONTRACTION

16 - CONTROL OF COORDINATED MOVEMENTTHE CEREBELLUM / THE LEARNING OF SPORTS SKILLS

17 - CONTROL OF COORDINATED MOVEMENTRECIPROCAL INNERVATION

18 - SKELETAL MUSCLE ANATOMYTENDON / CONNECTIVE TISSUE / FASCICULI / MUSCLE FIBRE / MYOFIBRIL / SARCOMERE

Unit 6 A.1.3


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ENERGYDEFINITIONS

ENERGY• is the capacity to do workWORK• = force x distance moved• measured in joules JCHEMICAL ENERGY• is energy that is produced by a complex series of chemical

reactions• which can then be made available as :KINETIC ENERGY• is energy due to movement• which results from muscular contractionsPOTENTIAL ENERGY• is stored energy due to gravityPOWER• is the rate at which energy is used• the energy used per second• unit watt W

Energy Concepts

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ENERGY CONCEPTS

APPLICATIONS• warming-up • the construction of training

programmes• prevention of fatigue• delay of fatigue• recovery from fatigue• nutrition• performance• bodyweight control• body temperature maintenance

GENERAL CHARACTERISTICS• measurement of energy

expenditureDIRECT METHOD• involves burning of food• and measuring heat energy

producedINDIRECT METHOD• involves measurement of oxygen

consumed or oxygen uptake during exercise

RATES OF ENERGY EXPENDITURE (per kg of body mass)

• above basal requirements - kJ kg-1 min-1

sitting at rest 0.14walking 0.2jogging / swimming (moderate) 0.6cycling (moderate) 0.46vigorous exercise 0.8

Energy Concepts

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INVESTIGATIONS

RUNNING UP STAIRS (Margaria Staircase Test)

• energy gained = weight x height• power = energy (joules)• time taken (sec)• answer in watts

ENERGY VALUE OF FOOD EATEN• calculate full energy value of food eaten• compared with measured energy output• results show that only a small proportion of

the energy is converted into useful work

Energy Concepts

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ENERGY CONCEPTS

Energy Concepts

ENER GY

sports activitiesand the energy

continuum

generalcharacteristcis

defi nitions

applications

the recoveryprocess

fuel forexercise

ATP

ATP - PC system(alactic)

lactic acid system

aerobic system

system 1

system 2system 3

m olecular m usclecell structures

Unit 6 A.1.7


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METABOLISM

ENERGY METABOLISM• total intake of food sufficient to supply enough energy to :

– keep cells alive– keep systems working– meet demands of life

BASAL METABOLIC RATE (BMR)• this is the least rate of energy usage needed to carry out basic

body functions• measured after lying down after 8 hours sleep / 12 hours fasting

TOTAL METABOLIC RATE• sum of BMR + energy required for all daily activities

Energy Concepts

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MOTOR NEURONE STRUCTURECELL BODY• includes nucleus and cytoplasm• membrane is receptive to stimuli from other

neurones

Molecular Muscle Cell Structures

DENDRITES• highly branched processes which extend

out from the cell body• specialised to receive stimuli from

sensory organs or from other neurones

AXON• conducts nerve impulses to other cells

(nerve, muscle, gland cells)• special structures include :

– myelin sheath insulates nerve– nodes of Ranvier are gaps in myelin

sheath where action potential jumps from node to node

– axon terminal ends with synaptic end bulbs containing neurotransmitter substances

– enabling action potential to be applied to adjacent cells

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AN ACTION POTENTIAL• transmission of neural messages along a

neurone is an electrochemical process• an action potential is initiated when sufficient

numbers of Na+ ions diffuse into the neuron


TRANSMISSION of NEURAL IMPULSE

• this depolarises the axon to a critical threshold level

• called the all-or-none law

• followed by repolarisation back to the resting potential

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TRANSMISSION of NEURAL IMPULSECONDUCTION of an ACTION POTENTIAL in a MYELINATED AXON• the myelin sheath insulates the axon• the action potential travels from node to node in a wave-like action

The MYELIN SHEATH offers :• increased conduction velocity• less costly in terms of ion run-down• since ion exchange only occurs at the nodes of Ranvier

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The MOTOR END PLATEFUNCTION• to transfer an impulse from the motor

neurones to the muscle fibre block• this causes all muscle fibres attached

to this end-plate to contract


TRANSMISSION of NEURAL IMPULSE

The ALL OR NONE LAW• stimulation of the motor

neurone will result in contraction of ALL the fibres in that motor unit

SYNAPSE• a junction where the axon of

one neurone interacts with another neurone

ACTION• nerve action potential is followed by the

muscle action potential• a delay of 0.5 milliseconds occurs due to

release of transmitter substances (such as acetylcholine from synaptic knobs) which initiate the muscle action potential

• the area of depolarisation travels down muscle cell passing the entrances to ‘T’ vesicles which secrete Calcium ions needed to initiate muscle contraction

• each different fibre type (slow twitch, fast twitch etc) is innervated by a separate and different type of motor neurone

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Ach= Acetylcholine

Molecular Muscle Cell StructuresIMPULSE TRANSMISSION at a NEUROMUSCULAR JUNCTION

Unit 6 A.1.13


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PRODUCTION OF COORDINATED MOVEMENT

MOTOR NEURAL FIRING PATTERNS• all-or-none law• all fibres associated with a single motor unit are fired at

once• different fibre groups (attached to different motor units) are

fired at different times

SINGLE FIBRE TWITCH

WAVE SUMMATION• the same fibre group fired repeatedly will build the force

exerted by wave summation


Unit 6 A.1.14


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PRODUCTION OF COORDINATED MOVEMENTMOTOR NEURAL FIRING PATTERNSMULTIPLE FIBRE TWITCHES

SPATIAL SUMMATION• different fibre groups are fired in succession to control a movement• the total force across the space of a muscle is the sum of the

effect of different fibre groups


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PRODUCTION OF COORDINATED MOVEMENT

MOTOR NEURAL FIRING PATTERNSMULTIPLE FIBRE TWITCHES

GRADATION OF CONTRACTION• refers to the ability of muscle to produce forces • varying from very light to maximum force or tension• achieved in two ways :

– increasing the frequency of stimulus (wave summation)

– varying the number of motor units recruited• example in hockey :

– fine control of movement required for a flick– as opposed to the maximum effort required for a full hit


TETANIC CONTRACTION• no time for relaxation between motor unit firing• causes complete lock up of muscle

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CONTROL OF COORDINATED MOVEMENT

THE CEREBELLUM• the balance of fine and gross control is under the control of the

CEREBELLUM• to produce smooth coordinated movement, the cerebellum

compares the intended movement with the actual movement (from sensors within the moving structure)

• if a difference is detected, the cerebellum sends impulses to the appropriate motor units in the spinal cord which would produce a correction

THE LEARNING OF SPORTS SKILLS• in sport, the cerebellum is involved in the learning of fine

motor skills (as in archery) or gross motor skills (as in weight lifting)

• gross movements use leg and arm muscles having about 1000 muscle fibres associated with one motor unit

• fine movements (of the eyes and fingers for example) require muscles with far fewer (10 - 100) muscle fibres controlled by a single motor unit


Unit 6 A.1.17


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CONTROL OF COORDINATED MOVEMENT

CONTROL• control is achieved by changing the frequency of stimulus -

wave summation• by increasing or decreasing the number of motor units

in operation - gradation of contraction• and as a result of different motor units being activated in

turn across a muscle - spatial summation• to enable very small forces to be maintained if required• and changes in muscle forces to occur

RECIPROCAL INNERVATION• this is the self-regulation of rhythmic movements between

one muscle and its antagonist• control of movements requires regulation of relaxation of

antagonists during dynamic activity of an agonist


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TENDON• dense connective tissue• attaches muscle to boneCONNECTIVE TISSUE• called fascia (epimysium,

perimysium, endomysium)• holds muscle tissue together• allows free movement• stabilises nerves and blood

vesselsFASCICULI• bundle of muscle fibresMUSCLE FIBRE• muscle cell contains many myofibrils• several nuclei inside sarcolemma• mitochondria positioned throughout• sarcoplasm contains fat / glycogen stores, myoglobin, PC,

ATPMYOFIBRIL• protein filamentsSARCOMERE• the basic contractile unit


SKELETAL MUSCLE ANATOMY

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STRUCTURE• called STRIPED or STRIATED

muscle• every muscle cell is long and thin

called a MYOFIBRIL• this runs lengthways down the

muscle• each muscle cell has several nuclei

just under the SARCOLEMMA

PHYSIOLOGY• voluntary• neurogenic

(actively controlled by thoughts of sportsperson, and innervated by action of nervous system)

• DEPOLARISATION (in the motor end plate) stimulates energy release

• this energy provides the work necessary for muscle contraction



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STRUCTURES INVOLVED• the motor unit• VESICLES in cell sarcoplasm pump

out CALCIUM ions (Ca++)• Ca++ activates ATPase• this releases energy bond by

ATP -> ADP + Pi + energy

• this occurs in MITOCHONDRIA



SARCOPLASMIC RETICULUM (SR)• a network of tubules and sacs in muscle cells• these t-tubules transmit muscle action potential to myofibril• the SR is also a storage site for Ca++

TROPOMYOSIN• long protein molecule that covers active myosin sites enabling actin to

bind to myosin during contraction of the muscleTROPONIN• a molecule spaced at intervals along actin filaments• at rest troponin holds the tropomyosin in position to prevent exposure of

the myosin binding sites on actin filaments

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STRUCTURE and PHYSIOLOGY of MUSCLE CELL CONTRACTION

STRUCTURE of a SARCOMERE• the Z lines are the ends of the sarcomere• which are attached to actin filaments which

comprise the I zone of the relaxed unit• the myosin filaments lie in between actin

filaments which they just overlap (relaxed)• the H zone is the space between the ends of

the actin filaments


CONTRACTION• during contraction the cross-bridges

between the myosin and actin filaments pull them towards one another

• this increases the overlap and pulls the Z lines towards one another

Unit 6 A.1.22


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PHYSIOLOGY of MUSCLE CELL CONTRACTION

EXCITATION and CONTRACTION• a neural action potential travels via a motor

neurone to the motor-end plate • to create a muscle action potential over the muscle

fibre’s sarcoplasm• and inward along the ‘T’ tubules• triggering the release of Ca++ from

‘T’ vesicles (located within SR) into the sarcoplasm

• where it binds to a troponin molecule on an actin filament

• tropomyosin molecules on the thin actin filament move exposing actin’s active sites

• energised myosin cross-bridges bind to actin’s active sites

• and use their energy (released from ATP) to pull the thin actin filaments towards the centre of the sarcomere (called the power stroke)

• attach, detach, reattach of cross-bridges is called the ratchet mechanism

• this cycle repeats itself as long as ATP is available• when fully contracted the H zone disappears


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PHYSIOLOGY of MUSCLE CELL CONTRACTION

RELAXATION• after the impulse is over, the SR actively pumps Ca+

+ back into its sacs• tropomyosin returns to its position• blocking actin’s active sites• muscle fibre returns to its resting length


Unit 6 A.1.24


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STRENGTH OF MUSCLE CONTRACTION

FACTORS AFFECTING THE STRENGTH OF MUSCLE CONTRACTION

Muscle Strength

STR EN GTH O FMUSC LE

C O N TR A C T I O N

m etabo lic condition(fatigue)

recruitm ent o fm otor units

(num ber o f fibresactivated)

in itial length o fm uscle fibres

(length tensionrelationship)

am ount o f load(stretch reflex)

Unit 6 A.1.25


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ATP

ATP - ADENOSINE TRIPHOSPHATE

• ATP is the energy currency linked to intensity and duration of physical activity

• ATP exists in every living tissue• its breakdown gives energy for all life functions

• energy released during tissue respiration is stored in the chemical bonds in ATP

• energy is released during the reaction :

• ATP --> ADP + Pi + energy

• ATPase is an enzyme which facilitates this reaction• ADP is adenosine diphosphate• the reaction is exothermic - it releases energy

• the supply of ATP in muscle (and other tissue) will only last for 2 seconds if vigorous exercise is undertaken

• therefore ATP needs to be regenerated by other chemical reactions if exercise is to continue past 2 seconds

• example : an exercise like standing long jump would use energy from stored ATP

Energy Systems and the Energy Continuum

Unit 6 A.1.26


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ATP

RESYNTHESIS OF ATP

• ATP is resynthesised from ADP within the following reaction :

• energy + ADP + Pi ---> ATP

• this is an endothermic reaction - energy is given to the molecule to enable the reaction to happen

• this energy will be derived from food fuels

• there are 3 main systems by which this resynthesis occurs


resynthesis o f A TP fromA DP, P i and energy

ATP - PC system(alactic)

lactic acid system

aerobic system

Unit 6 A.1.27


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ATP / PC ALACTIC SYSTEM - THE PHOSPHOCREATINE SYSTEM

ATP / PC SYSTEM

• for activity which lasts between 3 and 10 seconds

• for high intensity maximum work

• example : flat out sprinting - 100m sprint

• no oxygen is needed - ANAEROBIC

• the chemical reactions within this system are a coupled reaction


Unit 6 A.1.28


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THE COUPLED REACTION

• ATP is resynthesised via phosphocreatine (PC)• PC is stored in muscle cell sarcoplasm

• the following reactions takes place :

• PC ---> Pi + C + energy

• energy + ADP + Pi ---> ATP

• the two reactions together are called a coupled reaction

• these reactions are facilitated by the enzyme creatine kinase

• the net effect of these two coupled reactions is :• PC + ADP ---> ATP + C

• PC is recreated in muscle cells during the recovery process

• this requires energy and is an endothermic reaction

Unit 6 A.1.29


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EFFECTS OF TRAINING ON THE ALACTIC ANAEROBIC SYSTEM

• muscle cells adapt by :– increase in ATP and PC stores

• therefore the ATP / PC system provides energy for slightly longer

• when exercise is taken at maximum effort• the alactic / lactic threshold is delayed

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THE LACTIC ACID SYSTEMTHE LACTIC ACID SYSTEM

• depends on a chemical process called GLYCOLYSIS• glycolysis is the breakdown of sugar


• the breakdown of glycogen in this way is facilitated by the enzymes glycogen

phosphorylase (GPP), phosphofructokinase (PFK)

• this process is ANAEROBIC and takes place in the SARCOPLASM of the muscle cell

• no oxygen is needed

• the end product of this reaction (in the absence of oxygen) is lactic acid

• the enzyme facilitating the conversion from pyruvic acid to lactic acid is lactate dehydrogenase (LDH)

• carbohydrate is stored as GLYCOGEN in the muscles and liver

• the breakdown of glycogen provides the energy to rebuild ATP from ADP

Unit 6 A.1.31


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THE LACTIC ACID SYSTEMEFFECTS OF CONTINUED HIGH INTENSITY EXERCISE

• lactic acid accumulates• this produces muscle fatigue and pain• the resultant low pH inhibits enzyme

action and cross-bridge formation• hence muscle action is inhibited• physical performance deteriorates


EVENTS AND SPORTS• up to 30 - 60 seconds• 400m run• 100m swim• after exercise stops, extra oxygen is

taken up to remove lactic acid by changing it back into pyruvic acid

• the OXYGEN DEBT

TRAINING• develops body adaptations :

– the ability to tolerate higher levels of lactic acid– more glycogen is stored– the lactic acid / aerobic threshold is delayed

Unit 6 A.1.32


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THE AEROBIC SYSTEM

STAGE ONE - GLYCOLYSIS• this takes place in muscle cell SARCOPLASM• and is identical to the lactic acid system• ATP regenerated = 2ATP per molecule of glucose

STAGE TWO - KREB’S CYCLE (CITRIC ACID CYCLE)• occurs in the presence of oxygen• taking place in the muscle cell MITOCHONDRIA within the inner fluid

filled matrix• pyruvic acid (from glycolysis) promoted by enzymes of the citric

acid cycle, or fatty acids (from body fat) facilitated by the enzyme lipoprotein lipase or protein (keto acids - from muscle) act as the fuel for this stage

STAGE THREE - ELECTRON TRANSPORT CHAIN• occurs in the presence of oxygen• within the cristae of the muscle cell MITOCHONDRIA• hydrogen ions and electrons have potential energy which is

released to produce the ATP


Unit 6 A.1.33


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THE AEROBIC SYSTEM

STAGE ONE - GLYCOLYSIS


STAGE TWO - KREB’S (CITRIC ACID) CYCLE

• 2 molecules of pyruvic acid combine with oxaloacetic acid (4 carbons) and acetyl coA (2 carbons)

• to form citric acid (6 carbons)• the cycle produces H+ and electron pairs,

and CO2, and 2 ATP• fats and proteins enter the cycle

STAGE THREE - THE ELCTRON TRANSPORT CHAIN

• the H+ and electron pairs have potential energy

• which is released in a controlled step by step manner

• oxygen combines with final H+ ions to produce water and 32 ATP

Unit 6 A.1.34


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THE AEROBIC SYSTEM

AEROBIC RESPIRATION• the net effect is of an endothermic reaction

• glucose + 36 ADP + 36 Pi + 6O2 ---> 6CO2 + 36 ATP + 6 H2O

• fat fuels produce 2 ATP less than glucose

AEROBIC EXERCISE TYPES• low intensity, long duration activities• examples : game of hockey, 800m swim, long distance jog


Unit 6 A.1.35


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THE ENERGY CONTINUUM

THE ENERGY CONTINUUM• this describes the process by which

ATP is regenerated via the different energy systems

• depending on the intensity and duration of exercise

• each of the alactic, lactic acid and aerobic systems contribute some ATP during the performance of all sports

• one or other of the energy systems usually provides the major contribution for a given activity

• the diagram shows approximate proportions of ATP resynthesised via aerobic / anaerobic for some sporting activities


Unit 6 A.1.36


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THE ENERGY CONTINUUMOTHER FACTORS AFFECTING THE PROPORTIONS OF ENERGY SYSTEMS • used in any given exercise activity are :

– level of fitness (whether adaptations to training have included enhancement of relevant enzymes - which would for example postpone levels of lactate accumulation)

– availability of O2 and food fuels, for example a high CHO diet would assist replenishment

of glycogen stores which would then be available for glycolysis

VARIATION IN CONTRIBUTION OF ENERGY SYSTEMS• as time progresses during intense exercise, the following chart

shows the contribution of the different energy systems to the resynthesis

of ATP


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