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ENERGY CONCEPTS
CHEMICAL ENERGY: Plants convert SUNLIGHT into energy which is stored
within the BONDS of chemical COMPOUNDS or MOLECULES. This is then
passed to HUMANS in the form of FOOD. It is stored as CHO, PROTEIN or
FATS. We then further store this energy in a HIGH ENERGY compound called
ADENOSINE TRI-PHOSPHATE (ATP). ATP can be immediately used as
energy by the body. Energy found between the bonds of ATP is called ....
POTENTIAL ENERGY: This is when energy is ready to use, for example when
muscles CONTRACT. This energy is called …
KINETIC ENERGY: which is energy in the form of MOVEMENT.
ENERGY is the ability to perform WORK or put MASS into MOTION. In
human terms it means contracting muscles for physical activity. It is measured
in JOULES (J) which is equivalent to 1 NEWTON force or 1Kg acting over a
distance of 1 metre. It can also be measured in CALORIES and this is
equivalent to 4.18 Joules.
WORK is when a FORCE is applied to a body to move it over a distance.
WORK = FORCE (N) X DISTANCE MOVED (M) measured in Joules
POWER is the RATE at which WORK can be done. It is work divide by time.
POWER = WORK / TIME or (FORCE (N) x DISTANCE (M)) / TIME (secs)
The UNITS are WATTS (W). Force X Distance = PURE STRENGTH
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ADENOSINE TRI PHOSPHATE (ATP)
ATP is made up of a complex element called ADENOSINE and three simple
elements called PHOSPHATEs (P). These elements are held together by
BONDS which are HIGH ENERGY bonds. An ENZYME called ATPase breaks
the bonds between 2 of the Phosphates. When it does this it releases ENERGY
which is used for muscular CONTRACTIONS. This is an EXOTHERMIC
reaction because it RELEASES ENERGY as it progresses.
The COMPOUND which is left is called ADENOSINE DI PHOSPHATE (ADP).
If there is no ATP present then energy for work is not possible. The body only
has a LIMITED CAPACITY to store ATP. It can only last for 2 to 3 SECONDS
of work. After this time the body has to find a way of RESYNTHESISING
ADP back into ATP again. It has lost a Phosphate. ADP must find another to
REBUILD it an become reusable. This is an ENDOTHERMIC REACTION
because energy is REQUIRED from somewhere to progress.
The body has 3 ENERGY SYSTEMS with which to re-synthesise ADP to ATP.
The ATP / PC SYSTEM
The LACTIC ACID SYSTEM
The AEROBIC SYSTEM
Each system uses energy from one reaction to use in another reaction. This is
called a COUPLED REACTION
ENERGY SYSTEMS
• The 3 Energy Systems that re-synthesise ATP from ADP are the 1) ATP/PC
system 2) Lactic Acid System 3) Aerobic Energy System
• When ATP levels fall and ADP levels rise an ENZYME called CREATINE
KINASE is released and this breaks the PC bond in an EXOTHERMIC
reaction. This energy is used to re-synthesise ATP from ADP in an
ENDOTHERMIC reaction
1. The ATP / PC system can work ANAEROBICALLY as well as AEROBICALLY
but it does NOT require 02. It takes place in the SARCOPLASM of the cell.
However it can only supply enough PC to re-synthesise ADP to ATP for 3 to 10
seconds during MAXIMAL intensity. In recovery, Creatine and Phosphate (Pi)
are re-synthesised back to PC
TRAINING ADAPTATIONS: Anaerobic Training overloads the ATP / PC
system and increases the muscle’s ATP and PC stores which delays the
THRESHOLD between using this system and the Lactic Acid System by 2 secs
ADVANTAGES: No 02, Quickly Available, Quick Reaction, Explosive,
Powerful, No Fatiguing By Products, PC re-synthesised quickly
DISADVANTAGES: Stores are small, 1PC re-synthesises 1ATP, Only energy for
8 – 10 secs
ENERGY SYSTEMS
2) The LACTIC ACID SYSTEM: This system uses GLYCOGEN to re-synthesise
ADP back to ATP. The energy released through breaking down glucose is used
to do this. This is also a COUPLED and ENDOTHERMIC reaction. Glucose is
CHO in the body and when it is stored it is called GLYCOGEN. The decrease in
PC stores activates the ENZYME GLYCOGEN PHOSPHORYLASE which
breaks down the glycogen into glucose. It is then further broken down into
PYRUVIC ACID in a process called GLYCOLYSIS. The process takes place in
the SARCOPLASM, does not require 02 and is called ANAEROBIC
GLYCOLYSIS. This process releases 2 ATP from one glucose molecule
During Glycolysis the ENZYME PHOSPHOFRUKTIKINASE (PFK) causes
the breakdown into Pyruvic Acid but without 02 this breaks down further into
LACTIC ACID by the ENZYME LACTATE DEHYDROGENASE (LDH). This
process re-synthesises energy for 2 – 3 minutes of high intensity exercise but if
activity is MAXIMAL it will only last 30 seconds
ADVANTAGES: Relatively QUICK, no 02 required, Glycogen readily available
DISADVANTAGES: OBLA, Inhibition of ENZYMES due to lower Ph,
increased FATIGUE, stimulates PAIN receptors
TRAINING ADAPTATIONS: Overloading this system will increase LACTATE
BUFFER and delay OBLA
ENERGY SYSTEMS
3) The AEROBIC ENERGY SYSTEM: This has 3 stages to re-synthesise ATP. All
3 systems require 02 to break down 1 molecule of Glucose
STAGE 1: AEROBIC GLYCOLYSIS: This is the same process as anaerobic
glycolysis but instead the presence of 02 INHIBITS the accumulation of
LACTIC ACID. The 02 uses PYRUVIC ACID and this combines with
‘CoENZYME A’ to become ‘ACETYL CoENZYME A’. This takes place in the
SARCOPLASM.
STAGE 2: KREB’s CYCLE: The ‘ACETYL CoENZYME A’ now combines with
OXALOACETIC ACID to form CITRIC ACID in the MITOCHONDRIA. This is
then broken down to produce 4 EVENTS 1) C02 is produced and removed 2)
HYDROGEN ATOMS are removed (Oxidation) 3) OXALOACETIC ACID is
regenerated which is used again 4) Energy is produced to re-synthesise 2 ATP
STAGE 3: The ELECTRON TRANSPORT CHAIN (ETC): HYDROGEN
ATOMS released in Stage 2 combines with CoENZYMES NAD and FAD to
form NADH and FADH. These are carried down the ETC where HYDROGEN
is split into HYDROGEN IONS (H+) and HYDROGEN ELECTRONS (e-).
This takes place in the MITOCHONDRIA and 3 EVENTS follow 1) e- split
from the atom and pass down the ETC 2) This provides ENERGY to synthesise
34 ATP 3) H+ combines with 02 to form water (H20)
ENERGY SYSTEMS
ADAVANTAGES: large GLYCOGEN & FFA stores, 02 supply Large synthesis,
High DURATION (3 mins to 1 hr), No fatuiging BY PRODUCTS (C02/H20)
DISADVANTAGES: Slower Resynthesis, Requires 15% more 02 supply for
FFAs, COMPLEX reactions, Initial DELAY of synthesis at start of activity,
Limited ENERGY during high intensity activity
FATS (TRIGLYCERIDES) are broken down by ENZYME LIPASE into FFAs
which are the broken down into ACETYL CoA. This is where it enters the
KREB Cycle. They can produce more Acetyl CoA than Glucose but require
15% more 02. TRAINING increases Glycogen in muscle and liver, increases
mobilisation of Enzymes and uses FFAs early = Aerobic Threshold increased
• TOTAL ENERGY YIELD from the Aerobic System is 38 ATP from one
molecule of Glucose
• 2 ATP from Anaerobic Glycolysis
• 2 ATP from the Kreb’s Cycle
• 34 ATP from the ETC
EQUATION for AEROBIC RESPIRATION:
C6 H12 O6 + 6O2 = 6C02 + 6 H20 + ENERGY (for 38 ATP re-synthesis)
Glucose is completely broken down in the Aerobic system by 02 into C02 and H20
ENERGY CONTINUUM
• The Energy Continuum is a GRAPHICAL display of how the energy systems
INTERACT together to provide energy for the re-synthesis of ATP. It
highlights the PERCENTAGE of each of these 3 systems relating to both the
DURATION and the INTENSITY of the activity.
• Each sport/physical activity requires di8fferent percentages from each system.
They RARELY work in ISOLATION. Some activities are mainly AEROBIC
whilst others are ANAEROBIC. Most use a COMBINATION of all 3
Draw the following graph to represent how the Energy Systems Interact.
X Axis = Time in minutes from 0 to 360 seconds and the Y Axis = Capacity of
Energy System in % from 0 to 100%. Plot the following data for 3 lines
1) ATP / PC System (12, 98) (16, 50) (22 ,5)
2) Lactic Acid System (Anaerobic Glycolysis) (2, 1) (15, 60) (20, 95) (45, 98)
(120, 93) (180, 50) (240, 35) (300, 25)
3) Aerobic Energy System (10, 10) (20, 25) (120 , 40) (300, 70) (360, 98)
Highlight the points at which the PREDOMINAT energy system changes
THE 6 FACTORS THAT AFFECT THE TYPE OF ENERGY SYSTEM USED
1) INTENSITY and DURATION of the exercise: when the intensity is
ANAEROBIC HIGH INTENSITY SHORT duration the system will be ATP/PC
When intensity is LOW and duration is LONG the system will be AEROBIC.
When intensity reaches a point that the aerobic system cannot be used it uses
the LACTIC ACID system but this produces LACTIC ACID. The LACTATE
THRESHOLD crossed when blood lactate is above resting levels. When blood
lactate reaches 4mmol/L and above then OBLA has been reached. Fatigue will
occur
2) ENERGY SYSTEM THRESHOLDS: a threshold is the POINT at which an
energy system is taken over by another. ATP/PC system is 2-10seconds. ATP /
PC changes to Lactic Acid System at 10 – 90 seconds. Lactic Acid to Aerobic
System changes at 90 seconds to 3 minutes. After this it is the Aerobic System
unless INTENSITY is high.
3) 02 AVAILABILITY: As long as 02 supply is there the Aerobic System will resynthesise ATP. If there is INSUFFICIENT 02 the LACTIC ACID system will be
used. This is dependent on Respiratory and CV EFFICIENCY
THE 6 FACTORS THAT AFFECT THE TYPE OF ENERGY SYSTEM USED
4) FUEL AVAILABILITY: PC will be used for SHORT, HIGH intensity activity.
Duration cannot be sustained when PC stores DEPLETE and intensity remain
HIGH. PACING can conserve PC stores and RECOVERY periods can resynthesise them. GLYCOGEN is the MAJOR fuel for the first 20 minutes of
activity. It is readily available in the muscles and requires 15% less 02 than
FFAs. It takes 2-3 minutes to use this though as sufficient 02 has not had time.
Between 20 – 45 minutes FFAs will be broken down as well but only if
intensity is LOW because of the need for 15% more 02. High LIVER
GLYCOGEN levels will allow the athlete to maintain a higher intensity After 2
HOURS glycogen is DEPLETED and FFAs must be used. Unless athletes
reduce intensity to allow 02 supply they may HIT THE WALL.
5) ENZYME ACTIVATION LEVELS: Reactions cannot take place without them.
CREATINE KINASE is released when ADP increases and ATP decreases. This
activates the PC system. PFK is released when PC decreases and this activates
the Lactic Acid system. PFK is also released when ADRENALIN increases and
INSULIN decreases, activating the AEROBIC system
6) FITNESS LEVELS: The more aerobically fit an athlete is the better 02/C02
transport which is essential to break down glycogen and FFAs. Conserving
glycogen is crucial to delay OBLA and aerobic and lactate THRESHOLDS
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THE RECOVERY PROCESS
The Recovery process is concerned with the events AFTER exercise. It is
important DURING exercise to allow performers to MAINTAIN performance
and also AFTER exercise to SPEED UP their recovery. The aim is to
RESTORE the body to its PRE EXERCISE STATE by removing BY
PRODUCTS and by the REPLENISHMENT of FUELS.
After exercise the body does not return immediately to its pre exercise state.
RESPIRATION and HEART RATE remain elevated. This is known as EPOC
(EXCESS POST EXERCISE 02 CONSUMPTION) or 02 Debt. It has 2 STAGES:
ALACTACID DEBT: (RAPID RECOVERY Stage) This restores stores of
PHOSPHAGEN and the re-synthesis of ATP , PC, MYOGLOBIN and Hb. It
requires approximately 3-4 Litres of 02 and takes about 3-4 minutes but 50%
are restored in 30 seconds and 75% restored in 1 minute
LACTACID DEBT: (SLOW RECOVERY Stage) Early research thought this
was responsible for the removal or re-conversion of LACTIC ACID into either
PYRUVIC ACID (which can be used as fuel) GLYCOGEN or PROTEIN. Now
it is thought that it supports A) METABOLIC FUNCTIONS such as HIGH
TEMPERATURE, B) remaining HORMONES such as adrenalin, and C)
elevated CARDIAC OUTPUT to reduce temperature. It requires 5-8 Litres of
02 and can take between 1-24 hours depending on the exercise intensity
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THE RECOVERY PROCESS
Increased levels of C02 formed during exercise is removed as CARBONIC
ACID, CARBOAMINOHAEMOGLOBIN, or in the PLASMA. The
CHEMORECEPTORS stimulate the RCC and the CCC to ensure that
respiration and heart rate are ELEVATED during recovery to assist C02
removal.
A major factor of MUSCLE FATIGUE is GLYCOGEN DEPLETION. Most can
be REPLENISHED within 10-12 hours after exercise. Complete recovery can
take 2 DAYS in prolonged endurance events. FAST twitch fibres can replenish
quicker. CARBOHYDRATES in recovery are crucial for this to happen
Draw the following graph for Glycogen Depletion: X axis = Time of Exercise
(0 to 1 hour )and Recovery (0 to 24 hours). Y axis = Muscle Glycogen % (0 to
100%)
Plot the following:
A) Exercise Time 0 mins = 100%, 1 hour = 30 %
B) Recovery Time 4 hours = 50%, 8 hours = 60%, 12 hours = 70%, 16 hours
= 77%, 20 hours = 83%, 24 hours = 90%
Label the graph