Fuel for Energy
Primary source of energy
All carbohydrate is ultimately broken down to
glucose or stored in the muscle or liver as glycogen
Dietary sources of starches and sugar to replenish
Large source of energy during prolonged, less
Rate of energy release is slow.
Less readily available for cellular metabolism because
it must be reduced from its complex form.
Minor energy source
Utilized during severe depletion of the other
macronutrients or during starvation.
It can be used to generate free fatty acids FFAs for cellular
Or converted to glucose through the process of
It can supply 5 to 10% of the energy needed to sustain
Fuel for Energy
Three Energy Systems
Immediate (ATP – Phosphocreatine System)
Short Term (Glycolytic System)
Long Term (Oxidative System)
ATP – PCr System
Simplest of the energy systems.
This process does not require oxygen, but it can occur in
the presence of oxygen.
During the first few seconds of intense muscular activity
(sprinting), adenosine triphosphate (ATP) is maintained at
a relatively constant level as phosphocreatine (PCr)
Combination of ATP and PCr stores can sustain the
muscles energy needs for up to approximately 15 sec of an
all out sprint.
Short term system
Liberation of energy through the breakdown of
Anaerobic glycolysis entails a complex process
involving 10 – 12 enzymatic reactions for the
breakdown of glycogen to lactic acid.
Does not produce large amount of ATP.
Predominates during early minutes of high intense
exercise (all out sprint for 1 – 2 min).
Long Term System
Most complex of the three system
Slow to turn on, but has a tremendous energy –
Primary method of energy production during
Oxidation of Fat
Triglycerides - major
Lipolysis carried out by
Beta Oxidation – Enzymatic
catabolism of fat by the
FFA is cleaved to acetic acid
Oxidation of Protein
Conversion into intermediates (pyruvate / acetyl
Energy yielded approx. 4.1 kcal/g
Interaction of the three
Do not work independent of each other.
Each system contributes to the total energy needs of
One system usually predominates, depending on the
Running Event Immediate Short Term Long Term
100 m 95 3 2
200 m 95 2 3
400 m 80 15 5
800 m 30 65 5
1,500 m 20 55 25
3,000 m 20 40 40
5,000 m 10 20 70
10,000 m 5 15 80
5 5 90
Percentage of Emphasis on the Three Metabolic Energy Systems in Training
For Various Running Events