Notes on Energy Systems

Notes for Physical Education

The Energy Systems

What is ATP

* When food is consumed some compounds contain energy

* Body can not access energy directly and so is used in the form of Adenosine Triphosphate (ATP)

* When ATP is broken down it releases energy

Sources of ATP

Protein-

* Food including meat, fish, dairy, eggs

* Only used as ATP in conditions of prolonged starvation

Carbohydrates-

* Breads, cereals, fruits and pasta

* Broken down into glucose and stored as glycogen in liver and muscles

* Excess CHO converted into fat and stored in adipose tissue

Fats

* Broken down into Fatty Acids and triglycerides

* Fatty acids stored in adipose tissue pr circulate in the blood

* Triglycerides stored in the muscles

Functions of ATP

* Energy is stored in chemical bonds between two major ATP parts- ADP (adenosine diphosphate) and the third phosphate.

* When electrical impulses at muscle stimulates ATP to break down into ADP

* Used to power rowing motion of myosin cross bridges (muscle contracts)

* Only small amounts of ATP in muscles

* Once store is used up, chemical reactions occur to produce ATP

Production of ATP

* 3 chemical methods of producing ATP inside our muscles; 1) from the energy released from the break down of Creatine Phosphate, 2) from energy released when glucose is converted into lactic acid, 3) breakdown of CHO and fats using oxygen

ATP production during resting conditions

* Any ATP required is produced aerobically

* Occurs in mitochondria

* At rest two fuels for aerobic energy production ; fats (two thirds) and CHO (one third)

ATP production during exercise

* Depends on how long exercise (duration), wether or not vigorous exercise (intensity) and how well developed the persons cardio-respiratory system is.

* Anaerobic only used when not enough oxygen to produce ATP is required.

ENERGY SYSTEMS

The ATP-CP system

* supplies immediate energy

* for maximal intensity and short periods (10seconds)

* a molecule called Creatine Phosphate breaks down into Creatine and phosphate which releases energy used to rejoin ADP and phosphate to make ATP

* very limited supply

Lactic Acid System (anaerobic glycolosis)

* once CP stores become exhausted second anaerobic energy system takes over

* stored glycogen obtained from CHO is converted into glucose

* Then converted into pyruvic acid if not enough oxygen is supplied then lactic acid is formed.

* Then converted into lactic acid.

* After large build up of lactic acid fatigue and muscle discomfort set it.

* Short term energy 20-90 seconds

* Also supplies energy in short period beginning of longer activity.

Aerobic System

* During exercise respiratory rate, tidal volume (depth of each breath), heart rate, stroke volume, cardiac output and arteriovenous oxygen difference all increase

* If exercise is sub-maximal eventually oxygen supply will be sufficient to produce required ATP

* Fuels for aerobic system are- glucose either from muscle tissue or from liver and fats- either triglycerides from the muscle or fatty acids from adipose tissue.

* During rest fats are primary fuel

* Glucose is primary fuel depending on the duration and intensity of the exercise

* Begins in the same manner as the lactic acid system- pyruvic acid is made but since sufficient oxygen is being supplied the pyruvic acid then is transported into the mitochondria

* By products- H2O and CO2

* Prolonged use of aerobic system results in depletion of muscle and liver glycogen stores

Oxygen Consumption and Delivery

Oxygen Delivery

* Major factors limiting aerobic performance- ability of lungs to take In large volumes of air, ability of blood to take up oxygen as it passes the lungs, ability of the heart to pump large volumes of blood to the muscles, ability of muscles to extract oxygen form the blood, ability of muscles to convert oxygen and fuels into ATP

Steady State

* Occurs during sub-maximal exercise

* When heart rate plateaus

* When the oxygen consumption matches the oxygen requirements

Maximum Oxygen Consumption VO2 MAX

* Process of increasing oxygen uptake and reaching a new steady state can continue eventually until a pace is reached that is so demanding that you can not reach a new aerobic steady state

* Volume of oxygen consumed by the body for energy production is called VO2

* Measured in litres of oxygen consumed