Energy Systems
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Types of energy
•Chemical
•Mechanical
•Heat
•Light
•Electric
•Nuclear
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Laws of Thermodynamics
• energy transfer always
proceeds in the
direction of increased
entropy and the release
of free energy
• 1- Energy cannot be
created or destroyed
– Chemical energy 
mechanical energy
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Definitions
• Enzymes
– Highly specific protein catalysts
– Accelerate the forward and reverse reactions
– Are neither consumed nor changed in the reaction
• Coenzymes
– Complex nonprotein organic substances
– facilitate enzyme action by binding the substrate
with its specific enzyme
– transport chemical groups from one enzyme to
another.
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Catabolism and Anabolism
Catabolism :
Metabolic pathways that break down
molecules into smaller units and release
energy
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Overview of Catabolism
FFA’s
Figure 3.4, simplified
Glucose
Amino acids
glycolysis
deamination
NH 2
Acetyl CoA
oxidation
TCA
Cycle
CO 2
FADH + H +
mitochondria
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NADH + H +
Electron
Transport
Chain
Anabolism
Covalent bonding of
electrons, protons and small
molecules to produce larger
molecules  building up
- Catabolism and anabolism
function in a dynamic balance.
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Anna
More definitions
• Exergonic is a spontaneous reaction that
releases energy.
• Endergonic is an anabolic reaction that
consumes energy.
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Energy systems
Generate ATP under different conditions
•ATP-PC
•Lactic acid/ glycolysis
•Aerobic/ Oxidative
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ATP- Adenosine Triphosphate
– Powers all of cell’s
energy-requiring
processes
– Potential energy
extracted from food
– Energy is stored in
bonds of ATP
– 80-100g is stored
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Energy Systems
• Immediate energy
 8 seconds
– ATP-PC
• Short-term energy
 1 or 2 minutes
– Lactic acid system
– Glycolytic system
– Anaerobic glcolysis
• Long-term energy
>3 minutes
– Aerobic system
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http://www.onlinestopwatch.com/full-screenstopwatch/
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ATP
• All gone after 2
seconds maximal
intensity
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ATP-PC system
• Anaerobic resynthesis
of ATP- 5-8 seconds of
energy
• Hydrolyzed by the
enzyme, creatine
kinase
• ADP is phosphorylated
to ATP
• Creatine may be
phosphorylated back to
PCr
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Adenosine Diphosphate
• ADP is ATP minus one phosphate group
• 14 calories of energy is released each
time ATP  ADP
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Remember the Spare
Phosphate??
• The Spare P that was
released from ATP 
ADP hooks up with
Creatine to form …
• Creatine Phosphate
(CrP)
• Cells store ~ 4 – 6
times more PCr than
ATP
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Creatine Supplementation
• If Phosphocreatine (PCr) is depleted, it
cannot regenerate ATP
• Ingestion Creatine monohydrate (20 g per
day) over 5 days  increased stores PC
• Therefore improves performance short
intense exercise in non weight bearing
exercise
• Also enhanced physiologic adaptation to
resistance training  Increased dynamic
muscular strength and muscle mass
• Beware of side effects  long term still
unknown
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Glycolysis
• During performances of short duration and
high intensity that require rapid energy
transfer that exceeds that supplied by
phosphagens
– 400-m sprint
– 100-m swim
– Multi-sprint sports
• Anything up to 3 minutes
• Lactate is the by product “Lactic acid system’
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Glycolysis
• Breakdown of glucose or
glycogen to form 2
molecules pyruvate and
4 ATP
• Requires 2 molecules
ATP for the process to
occur
• = Net gain 2 molecules
ATP
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Lactic acid? Lactate?
• Not the same
• Lactate that accumulates during anaerobic
metabolism does not cause acidosis
• Lactate  Pyruvate  Acetyl CoA 
Kreb’s cycle & Aerobic production ATP
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Lactic Acid System
• Blood lactate @ rest is
usually 1-2 mmol/L but can
rise to over 20 mmol/L
during intense exertion.
• Lactate accumulation
– rate of lactate production
exceeds the rate of lactate
removal
• Lactate removal
– Gluconeogenesisconversion to glucose
through Cori cycle in the liver
If oxygen present:
– Oxidation to pyruvate
• Fuels citric acid cycle
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Lactate Inflexion Point- LIP
• Intensity of exercise above
which anaerobic energy
system is required to meet
energy demands.
• Lactate accumulates as
removal cannot exceed
production
• Measurable as blood lactate
levels increase substantially
Page 109 of text
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Aerobic
• Oxidative
Phosphorylation
• Lipids
– Lipolysis
– Beta oxidation
– Kreb’s cycle
• Carbs
– Glycolysis
– Pyruvate  Acetyl CoA
– Krebs cycle (citric acid
cycle or tricarboxylic
acid cycle)
– Electron transport chain
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Krebs Cycle
• Also known as the TCA cycle, or citric
acid cycle
• Continues oxidation of
– Carbohydrates following glycolysis
– Fatty acids following beta oxidation
– Some amino acids following deamination
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http://www.youtube.com/watch?v=1aYPo5xNVIA
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Anaerobic/ aerobic systems
• 12 chemical reactions to convert
carbohydrate (either stored glycogen or
circulating blood glucose) to pyruvate
No Oxygen
Oxygen
Pyruvate converted to
Lactate
Pyruvate enters Krebs cycle
and is used to generate ATP
Produces 2-3 mol ATP
Produces 38-39 mol ATP
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What you need to know:
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Transition to Exercise
•
O2
consumption
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Recovery
-EPOC
• O2
consumption
remains
elevated
• O2 Dept =
payment for
O2 deficit
Pg 118 text
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Vo2 Max
• Determines
cardiovascular fitness
• O2 uptake increases
with intensity of
exercise up until a
certain point
• ml/kg/minute
• Factors influencing:
– Delivery
– uptake
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Yield: 1g = 4.1 Cal
Yield: 1g = 9.4 Cal
Yield: 1g = 4.1 Cal
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Metabolic pathway
Adaptation
Consequence
May improve recovery
Small Adaptations
Chronic
to Training
Mitochondrial
respiration
Glycogen
 Concentration
 Fuel for glycolysis
Glycolysis
 Activity of
phosphorylase
 Activity of PFK
 Rate of glycolysis
Small 
 Tolerance of intense
exercise
ATP
Metabolic pathway
Creatine
phosphate
Adaptation
Small 
Buffering capacity  Capacity
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 Rate of glycolysis
Consequence
 Capacity to rapidly
regenerate ATP
Delays fatigue from
acidosis
 ATP from glycolysis
Implications
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Sources of Fatigue- p 113 text
•
•
•
•
•
PCr depletion
Muscle glycogen depletion
Neuromuscular- nerve impulses
CNS- muscle recruitment
Metabolic by-products
– Lactate
– Hydrogen ions low ph
– Buffers- bicarbonate
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Muscle Fibre Types
• Type 1 = Slow twitch
– Generates energy aerobically
– For endurance exercise
• Type 2 = fast twitch
• 2a- some aerobic power / anaerobic
• 2b-predominantly anaerobic
– Generates energy anaerobically
– For short intense exercise
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Recovery from exercise
• Remove lactate
• Re-oxygenation muscle myoglobin
• Replace
– Muscle glycogen
– PCr
– Lipid levels
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Active recovery
• Movement at a lower intensity/ submax
performed immediately after exercise
• Assists with oxidation of lactate (Lactate
shuttling)
• But as is aerobic may impair
glycogen synthesis
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Passive recovery
• Lie down  complete
inactivity
• Theory is that this
‘frees’ oxygen for the
recovery process
• Downfall no lactate
shuttling
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Which is best?
• Research inconclusive
• Depends on exercise to recover from
• Steady rate exercise
– PCr stores not depleted
– Lactate levels not increased
– Depends on post exercise glucose intake
• Intense/Non-Steady rate exercise
– Large O2 deficit
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Lactate Removal
Exercise
Recovery
Active
Passive
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Passive
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Summary
• Energy is never created nor destroyed.
• Complex chemical process synthesize
glucose/ glycogen from our foods
• Immediate energyATP-PC
• Short-term energy Lactic acid system
• Long-term energy Aerobic system
• Dynamic balance
• Training
• Recovery
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