Fuel for Exercising Muscle

Fuel for Energy

Energy

Source

Carbohydrate

Fat

Protein

CarbohydratePrimary 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 carbohydrate reserve.

FATLarge source of energy during prolonged, less intense exercise.

Rate of energy release is slow.

Less readily available for cellular metabolism because it must be reduced from its complex form.

Protein 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 energy

Or converted to glucose through the process of gluconeogenesis.

It can supply 5 to 10% of the energy needed to sustain prolonged exercise.

Rate of Energy Release

Bioenergetics Phosphorylation

Anaerobic metabolism

Aerobic metabolism

Fuel for EnergyThree 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) declines.

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 glucose.

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 – yielding capacity

Primary method of energy production during endurance events.

Oxidation of Fat Triglycerides - major energy source

Lipolysis carried out by lipases

Beta Oxidation – Enzymatic catabolism of fat by the mitochondria.

FFA is cleaved to acetic acid

Oxidation of Protein

Gluconeogenesis

Conversion into intermediates (pyruvate / acetyl CoA)

Energy yielded approx. 4.1 kcal/g

Interaction of the three energy

systems Do not work independent of each other.

Each system contributes to the total energy needs of the body.

One system usually predominates, depending on the activity.

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

Marathon (42.2 km)

5 5 90

Percentage of Emphasis on the Three Metabolic Energy Systems in Training

For Various Running Events