Maribyrnong Secondary College

Physical Education

Energy Systems – Summary Sheet

The source of energy

- the only source of energy for muscle contraction is Adenosine Tri Phosphate

- energy is released in the reaction: ATP ð ADP + Pi + ENERGY

Sources of ATP

• Carbohydrate

- food sources - breads, pasta, cereals, rice and fruit

- converted to glucose in the blood

- stored as glycogen in muscles and liver

- major source of ATP production during exercise

• Fats

- food sources - diary products, meat, vegetable oils and nuts

- converted to fatty acids

- stored as triglyceride in fat cells located throughout body and within skeletal muscles

- primary source of ATP under resting conditions, used as a secondary source of energy during exercise

• Protein

- food source - meat, fish, diary products and eggs

- the building blocks of tissue

- basic structural units of proteins are amino acids

- found in muscle fibres and cell tissue

- not ordinarily used as a food fuel during exercise (may occur in ultra-endurance activities)

- carbohydrate is a more efficient fuel than fat in terms of ATP produced per molecule of oxygen consumed, BUT athletes engaged in long duration activity must also rely on fats in order to conserve the limited body reserves of carbohydrates.

The Energy System used is determined by :

* duration of exercise.

* intensity of exercise.

* (and person’s aerobic capacity ).

There are three energy systems :

* ATP / PC - very high intensity activity for very short duration.

- up to about 10 seconds.

- eg: shot put / gymnastics vault.

- ATP is broken down into ADP + P.

- the ATP is then resynthesised by phosphocreatine.

- the phosphocreatine ( PC ) is depleted in 10 seconds.

- PC stores can be replenished during rest periods.

*ANAEROBIC GLYCOLYSIS

- high intensity physical activity for short duration.

- 10 seconds to 1/2 minutes.

- eg: 200 m sprint / gymnastics routine.

- carbohydrates are broken down.

* AEROBIC - sub maximal physical activity for long periods of time.

- 3 minutes plus.

- eg: triathlon / 1500 m swim.

- carbohydrates and fats are broken down in the presence of oxygen.

- by products are carbon dioxide / water / heat.