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Concepts of Energy

Energy - Ability to perform work or put mass into motion (J)

Work - Ability to apply force over distanxe (N) FORCE x DISTANCE

Power - Rate at which we can work (W)

Adenosine Triphosphate (ATP)

  • Made up of Adenosine and three simple phosphates - held together by energy
  • Broken by the enzyme ATPase - releases energy (exothermic)
  • Stored in the muscles - quickly broken down

ATP Resynthesis

  • Reversible - Endorthermic (requires energy from either 3 energy systems) - coupled reaction - product from one used for another


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The ATP/PC (Alactic System)

  • Anaerobic
  • Uses ATP and PC
  • Found in the sarcoplasm - muscle cell
  • ATPase and Creatine kinase - control this
  • PC > C + Pi = E
  • Net total = 1 ATP

ATP broken down by ATPase..

When low levels of ATP and high levels of ADP..

Phosphocreatine is broken down by creatine kinase...

This produces energy...

and the phosphate can resynthesis ADP to ATP

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Advantages and Disadvantages


  • Does not require o2
  • PC is stored in muscle cel - avialable
  • Quick reaction
  • provides energy for explosive high intensity exercise and movements
  • No fatigue By products
  • PC quickly resynthesises


  • Only small amounts of ATP and PC
  • 1 PC resynthesises 1 ATP
  • Only provides energy for 8 - 10 seconds

Training adaptations

  • Anaerobic training increases body stores of ATP and PC
  • Delays threshold between ATP/PC and lactic acid system
  • Increase duration of high intensity activity to 1-2 seconds
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Lactic Acid System

  • Anaerobic
  • Uses Glycogen and Glucose
  • Found in the Sarcoplasm of the muscle cell
  • Enzymes used: Glycogen, phosphorylation, PFK, LDA
  • Processes: Glycogen to glucose - glucose to pyruvic + energy - to lactate acid
  • Lactic acid causes a Low pH which inhibits enzymes
  • Net Total = 2 ATP

Muscle / live glycogen transffered to Glucose by Glycogen Phosphorlyase...

Glucose converted into Pyruvic acid by phosphofructokinase... this releases energy....

Pyruvic acid is converted into Lactic Acid by Lactate dehydrongenase

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Advantages and Disadvantages of Lactic Acid System


  • Large glycogen store in muscle/liver
  • Resynthesises two molecules of ATP
  • Quicker supply of energy than aerobic
  • PFK and glycogen phosphorylation activated due to decrease of PC
  • Energy for high intensity exercise lasting between 10 and 180 seconds
  • Aerobically and anaerobically


  • Not as quick as ATP/PC system
  • Produces lactic acid
  • Reduces pH
  • Leads to muscle fatigue and pain

Training Adaptations :Increase body's tolenance to lactic acid, Increases bodys store of glycogen ,Delays OBLA prolonging threshold - work at a higher intensity

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The aerobic System

  • Aerobic Glycolysis: Aerobic, same as glycolysis HOWEVER pyruvic acid converted into coenzyme A - Acetyl coA (as there is o2) two moles of ATP
  • Krebs cycle: Aerobic, Acetyl CoA combines with oxaloacetic acid which makes citric acid...... In the matrix a series of reactions occur ....
  • CO2 is produced and removed via the lungs..
  • Hydrogen atoms are removed (oxidation)
  • Energy is produced to resynthesise two molecules of ATP
  • Oxaloacetic acid is regenerated.
  • Electron Transport Chain: Occurs in the cristae. Hydrogen atoms combine with coenzymes NAD and FAD = forming NADH and FADH
  • They are then carried down the electron transport chain..
  • Here Hydrogen is split into H+ and E- (provides suffiecent energy to resynthesise 34 ATP and H join with oxygen to make water
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Advantages And disadvantages of ETC


  • Large potential store of Glycogen and FFA stores
  • effiecent ATP resynthesis when good supply of o2
  • Large ATP resynthesis - 38 moles
  • Provides energy for a long moderate intensity for long duration
  • No fatiguing by-products


  • Slower rate of ATP resynthesis
  • Requires more o2
  • More complex series of reactions
  • cannot resynthesis ATP at start of exercise

Training Effects

  • Raised storage of muscle liver glycogen
  • Increase/prolong aerobic threshold
  • Improve efficency to remove lactic acid
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  • Fats are broken down by enzymes into free fatty acids and glycerol
  • FFA's are used as energy fuel within the aerobic system
  • They are broken down into Acetyl CoA....
  • They produce more Acetyl CoA then Glucose producing energy
  • HOWEVER requires 15% more oxygen
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Energy Continuum

Shows How energy systems interact to provide energy for the resynthesis of ATP

Highlights the predominance of each energy system

Factors affecting the energy systems used

  • 1) Exercise Intensity and duration - anaerobic (ATP/PC - lactic acid) aerobic (aerobic system)
  • 2) Energy system threshold - point at which is taken over by another system (ATP/PC - less then 10, Lactic -10 to 90 seconds, Aerobic - 3 +)
  • 3) o2 Supply - insufficient o2 - LA system sufficient - aerobic)
  • 4) Fuel Availabiliy - PC runs out first, Then glycogen then glycogen when there is insuffiicent oxygen
  • 5) Enzyme activation level - Without enzymes there would be no reactions and no energy for ATP resynthesis
  • 6) Fitness Level - More fit - more efficient their respiratory and cardiovascular system are. Aerobic threshold can increase - reach OBLA later
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Recovery Process

Aim is to restore the body to its pre-exercise state: by the removal of by-products and replenishment of fuels used up

After exercise respiratory and heart remain elevated which is the key process known as Excess post-oxygen consumption (EPOC) Oxygen level above what is at resting level during recovery required to restore the body to its pre-exercise state...Two stages of EPOC:

  • Alactacid Debt (rapid recovery) - restoration of phosphogen stores resynthesising ATP and PC. Also replenishing myoglobin and haemoglobin
  • Takes 3-4 litres of oxygen - takes 3 minutes
  • Lactacid debt (slow recovery stage) - removal of lactic acid which is converted into pyruvic acid or glycogen. This occurs by remaining high body temp, adrenalin, cardaic output
  • Requires 5-8 litres of oxygen and takes 24 hours
  • Co2 removal -elevated respiration and heart rate helps aid removal of co2 by blood plasma in red blood cells (carbonic acid) and haemoglobin
  • Glycogen replenishment - large amount can be restored up to 10 to 12 hours but all takes 2 days. a high carbohydrate diet can make it completly recovered within 1st 2 hours
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Implicatons of Recovery Process for sessions

  • Recovery process allows us to figure out work-relief ratio - interval training
  • This is more efficient as it increases the quality intensity of training within a training session
  • ATP/PC - Relief ratio is typically longer (1:3)
  • Lactate - Work ratio same as ATP/PC but decrease relief ratio (1:2)
  • Vo2 Max - Relief ratio is typically shorter (1:1)- work relief ratio longer in duration and intensity
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