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Chemical compound made up of adenosine and two phosphate molecules



Chemical compound made up of adenosine and three phosphate molecules
Energy released by splitting of third adenosine to create ADP and one inorganic phosphate



Situation where all three energy systems contribute to ATP production, with one system being the major contributor at any time


The food fuels

Carbs: glucose after digestion, primary source of energy
Fats: FFA's after digestion, secondary source of energy
Protein: amino acids after digestion, tertiary source of energy


Chemical fuel: ATP

- no ATP= no energy for muscle contractions= fatigue
- energy released when third phosphate molecule splits off
- only very small amount stored in muscles where it can be quickly accessed
- ATP resynthesised through use of energy from breakdown of PC or nutrients


Aerobic glycolysis

Breakdown of glycogen with sufficient oxygen releasing ATP, CO2, H20 and heat


Anaerobic glycolysis

Breakdown of glycogen with insufficient oxygen, releasing ATP, lactic acid, lactate and hydrogen ions



- can be broken down aerobically or anaerobically
- has more bonds than PC so takes longer to recharge ATP
- Preferred over fats as requires less oxygen to breakdown, allowing greater oxygen supply to working muscles
- use solely at maximal and predominant at sub max



- main source of fuel at rest
- can only be broken down aerobically because they are very large and take a long time to recharge ATP



Building blocks of tissue growth and repair
Used for energy in extreme circumstances as it requires a lot of oxygen to break down


Carbohydrate fat fuel mixture

During prolonged activities, body uses both carbs and fats
In the early stages, glycogen is primarily used but fats are the preferred fuel under these conditions, so the sooner FFA's are used, the greater the capacity of body to reserve glycogen for later stages


Lactate inflection point

- point when body can just prevent accumulation of hydrogen ions in working muscles
-maximal lactate production matched by maximal lactate removal
-beyond this point, lactic acid produced faster than it can be broken down, lactate accumulates in muscles and moves into bloodstream


Fate of lactate

- reconverted into Pyruvate and oxidised in muscle cells where it is produced

-enters bloodstream and used as a fuel by the heart and slow twitch muscle fibres where there are many mitochondria

-converted into glucose in liver which is used as energy or stored as glycogen


Oxygen deficit

- oxygen demand exceeds supply from systems at start of work
- as oxygen deficit continues, ATP obtained from anaerobic systems
-always occurs at the onset of exercise
-respiratory, cardiovascular and circulatory systems can't act quick enough to satisfy oxygen demand


Steady state

Oxygen supply meets demand
Contributes to lactate breakdown, removal and conversion back into useful forms


Oxygen debt/ EPOC

- at completion of work, ATP demand decreases dramatically but oxygen consumption still greater than resting
-active recovery extends oxygen consumption, helps in removal of metabolic by products
- OXYGEN DEBT = VO2 during recovery - resting VO2


Summary of ATP PC System

Fuel Source: phosphocreatine
Intensity: High, greater than 95% max HR
Duration of dominance: 1-5sec (peak power 2-4)
Speed of ATP production: explosive, instantaneous, small amounts
By Products: inorganic phosphates and ADP
Total Duration: 0-10 sec


Summary of Anaerobic Glycolysis system

Fuel Source: glycogen
Intensity: high intensity, greater than 85% max hr
Duration of dominance: 5-60sec (peak power 5-15 sec)
Speed of ATP production: fast but longer than ATP PC
By Products: lactic acid, hydrogen ions, ADP
Total Duration: 10-75 seconds


Summary of Aerobic system

Fuel Source: FFA (at rest) and CHO, fats and proteins (maximal/submaximal)
Intensity: resting and sub maximal, less than 80% max hr
Duration of dominance: greater than 75sec (peak 1-1.5min)
Speed of ATP production: medium, determined by oxygen availability, large ATP production
By Products: CO2, H20, heat
Total Duration: greater than 75sec


PC Depletion

- most common form of fatigue
- small amounts of ATP stored in muscles (1-2sec) and small amounts of PC (about 10sec) and a bit longer in larger muscles
- PC is split to put ADP and inorganic phosphate back together
- passive recovery of 30sec replenishes 70% of PC stores


Glycogen Depletion

- occurs during prolonged exercise exceeding 2hr duration and results in a failure to supply sufficient ATP for muscular contractions
-carbs used predominantly at max intensity and FFA at sub max
- muscle glycogen used first, then liver glycogen then FFA


Glycogen Depletion continued

-rate of ATP resynthesis decreases when body switches to FATS as major ATP producer at 2-3hr mark of prolonged endurance
-fats require more complex chemical reactions and more oxygen to break down
-This reduced oxygen availability at muscles for ATP production
- fats decrease speed of ATP resynthesis and increase risk of working anaerobically, high leading to fatigue


Accumulation of hydrogen ions and lactate

- anaerobic metabolism at high intensity and limited oxygen
-increases muscle acidity, inhibiting glycolytic enzymes- reducing rate of ATP resynthesis and therefore muscle contractions
-decreased calcium released within the muscles-reducing myosin coupling actin, resulting in muscles contracting with less force


Elevated body temperature

-evaporation is the main means of heat loss during exercise
-sweat is produced to provide bodily cooling
-as core temp increases: sweat increases. Blood redistributed away from working muscles to skin surface in order to maximise evaporative cooling via sweat. Less blood,oxygen,fuels flowing to working muscles, resulting in aerobic becoming increasingly anaerobic with less waste removed


Refuelling PC

- Passive rest relishes PC most rapidly
- Recovery needs to be either total rest or low enough intensity where PC isn't called upon
- Rate of restoration depends on amount depleted, more forceful contractions drain more PC
- 30s rest=70%, 180s=98%


Active recovery

-Maintains oxygen levels higher than rest: speed up H+ and lactate removal
-creates a muscle pump where the muscle presses on the blood vessels surrounding the working area, increasing the oxygen supply and waste removal
-prevents venous pooling and keeps blood circulating


Increasing LIP

-regular endurance training increases proportion of slow twitch fibres and increases the ability to oxidise glycogen and fatty acids in mitochondria
- >85% max HR approx LIP
- athlete able to exercise at a higher intensity aerobically, decreasing reliance on anaerobic glycolysis that is associated with fatiguing metabolic by products