INTRO TO ENERGY SYSTEMS

4 MAJOR STEPSTO PRODUCE ENERGY

• STEP 1 – Breakdown a fuel• STEP 2 – Produce ATP via energy

systems• STEP 3 - Breakdown ATP to release

energy• STEP 4 – Muscle contraction

Food ATP Energy

STEP 1 – BREAKDOWN OF FUELS

• The fuels are : Creatine Phosphate (CP), carbohydrate, fats and proteins.

• CP (ATP CP system)• Carbohydrate (Anaerobic glycolysis)• Carbohydrates, Fats and Proteins

(Aerobic Glycolysis)

ENERGY PRODUCTION

• Anaerobic - Produce ATP really quickly- quick, explosive energy for sprints, jumps, throws…- ATP PC system : energy from chemicals stored in

muscles- Lactic Acid system : energy from carbohydrates in food

eaten

• Aerobic - Produce ATP slowly- steady paced long activities such as jogging or cycling- Aerobic System : muscles use stores of carbohydrates

and combine them with oxygen to make energy. This system can also use fats and in extreme cases protein to produce ATP.

STEP 2 – PRODUCE ATP

• The role of the energy systems is ONLY to PRODUCE ATP. Energy release is not part of the energy systems formulas.

• ATP CP – produces ATP• LACTIC ACID SYSTEM – produces ATP• AEROBIC SYSTEM – produces ATP

STEP 3 – BREAKDOWN OF ATP

• Energy is stored in the chemical bonds between

the 2 major parts of ATP :ADP + the third phosphate

• An electrical impulse arrives at the muscle stimulates the ATP to break down into ADP and Phosphate and to release its energy, this energy is used to power the rowing motion of the myosin cross-bridges to make muscle contract

• Once the small amount of stored ATP in the muscles is used, energy is obtained from food – via the energy systems

STEP 4 - MUSCLE CONTRACTION

• The muscles used the energy released from the breakdown of ATP to fuel the contraction process.

STEP 4 - MUSCLE CONTRACTION

• 3 chemical methods of producing ATP in muscles: 1) energy released through breakdown

of creatine phoshate – ATP PC SYSTEM2) energy released when glucose is converted to lactic acid - LACTIC ACID SYSTEM3) breakdown of carbohydrates and fats using oxygen - AEROBIC SYSTEM

The 3 Energy Systems

• All 3 systems work at the same time but one system will be dominant depending on intensity, duration and type of exercise.

• Always use the word predominantly in your answers to Energy system questions.

• ATP is already in the muscle – when this runs out (about 2 contractions) energy systems must produce the ATP

Adenosine Triphosphate

• ATPDigested food is broken down into chemical

compounds – Carbohydrates, Fats and ProteinsThe energy contained in these food groups is

then used to form ATP (Adenosine Triphospahate)

• When broken down ATP releases energy for body functions eg organs, cell division and muscle contraction

FOOD FUELS

• PROTEIN (only used in the aerobic system) Food sources : meat, fish, dairy products and eggs Used to produce ATP only in extreme circumstances

• CARBOHYDRATES (used in both lactic acid and aerobic energy systems) Food sources : breads, cereals, fruits and pasta Broken down into glucose and stored as Glycogen

in the muscles and liver Excess is stored as fat Primary source of ATP for muscular contraction

during exercise

FOOD FUELS

• FATS (used in the Aerobic System) Food Sources : fast food, dairy products, nuts,

fatty meat Broken down to fatty acids (stored in adipose

tissue or blood) and triglycerides (stored in muscles)

Secondary choice of ATP for muscle contraction during exercise

Primary choice while at rest

Anaerobic Energy Systems

• The ATP PC Energy System• Used during supramaximal exercise, supplies ATP

very rapidly• Breaks down CP to produce ATP• The Creatine Phosphate stores, run out quickly so

this system cannot be relied on for very long.• Remember CP is broken down to produce ATP and

ATP is broken down to produce energy. For recovery (later) the reverse applies!

The ATP PC Energy System

• CP is stored within the muscle fibres to provide energy for maximal bouts of exercise up to six seconds in duration

• The high rate of ATP production corresponds to the ability to produce rapid forceful actions

• The low stores of CP breakdown allow it to primarily fuel the first six seconds of exercise

• After this, the CP system fuels less than 50% of ATP production and after this contribution quickly declines

The recovery of CP

• The recovery or resynthesis of CP stores in the muscle mainly takes place when the athlete stops exercise

• The research indicates that CP resysthesis during recovery is as follows

1. 30 seconds (50%) replenishment – fast phase2. 2-3 minutes (100%) replenishment – slow phase

We will discuss this further in Fatigue and Recovery.

Anerobic Glycolysis - Lactic Acid System

• Carbohydrate breakdown in this system does not require oxygen

• Lactic Acid is produced because oxygen is not present

• OBLA terminology confusing – varies greatly depending on methodologies of different scientists.

• The onset of blood lactic acid can occur at the same blood lactate level for both trained and untrained people, the difference lies in the amount of work able to be done before lactate accumulates (OBLA)

• OBLA is when the rate of lactic acid production is greater than the rate of removal

Aerobic Glycolysis

• During longer, submaximal efforts, oxygen is used to produce ATP from glycogen and fats – very rarely protein!

• The longer the event, the greater the supply of ATP from the aerobic energy system

ATP PRODUCTION DURING REST at rest ATP is

produced aerobically chemical reactions

to produce the ATP take place in the mitochondria within the muscles, the ATP is then transported to the myosin cross-bridges

food fuels – fats (2/3) and carbohydrates (1/3)

ATP PRODUCTION DURING EXERCISE During exercise the energy system

used to produce ATP depends on : How long you have been exercising -

duration At what intensity the exercise is The person’s aerobic fitness

1. THE ATP PC SYSTEM

ATP stored in myosin cross-bridges is broken down to release energy for muscular contraction , once this happens…

The ADP and the phosphate are converted back to ATP by the creatine phosphate

The creatine phosphate is broken down into creatine and phosphate molecules - which releases energy to resynthesise (ADP + phosphate) into ATP

ATP «—» ADP + P + energy CP

THE ATP PC SYSTEM (cont…)

The CP is exhausted after approx. 10 secs. of high intensity exercise – this energy system provides energy for events up to 10 secs.

The CP and stored ATP are restored after approx. 2 mins rest

• The creatine phosphate system provides ATP at the start of sub-maximal exercise and for high intensity activities such as sprints throws and jumps

2. THE LACTIC ACID SYSTEM

As CP stores are exhausted the lactic acid system begins to supply ATP

Stored glycogen (obtained from carbohydrates) is converted into glucose, then glucose is converted by enzymes into lactic acid, providing ATP in a

process known as anaerobic glycolysis Enzymes

Glucose--------------------Lactic Acid

3 ATP

THE LACTIC ACID SYSTEM….

During this process the lactic acid builds up in the muscles causing fatigue

The lactic acid is slowly removed and broken down into CO2 and H20

This system predominantly provides energy for a high intensity task lasting 10 seconds to 2 minutes e.g. 400 metre sprint

Also supplies some ATP in the early minutes of longer submaximal activity

THE LACTIC ACID SYSTEM….

Energy from breakdown of glycogen in muscle(glycogen>lactic acid+energy)

ADP + Pi -------------------- > ATP

Releases energy for muscle contraction

3. THE AEROBIC (OXYGEN) SYSTEM

For the first 1-2 minutes of longer activities the body meets the majority of it’s energy needs anaerobically. Beyond this time the body is able to take in enough oxygen to meet energy requirements aerobically – unless the intensity of the activity is above 85% max HR

This system uses firstly glucose from muscle tissue or the liver and secondly triglycerides from the ( muscle) and fatty acids (from adipose and the blood stream) which are carried to the working muscles

THE AEROBIC (OXYGEN) SYSTEM…..

Glucose or + O2 CO2 + Fatty acids H2O +heat +triglycerides

39 moles of ATP

This system is the major contributor of energy in continuous activities such as marathons, road cycling

races aerobics floor classes

INTERPLAY BETWEEN ENERGY SYSTEMS

• No sporting event relies on just one energy system to supply ATP. Most depend on a combination of the 3 with contributions varying at different stages of the event

• The body cannot suddenly switch from one energy system to another - there is a transition period where one energy system increases in importance while another, having performed its function, is decreasing

INTERPLAY BETWEEN ENERGY SYSTEMS…...

• The relationship between the energy systems differs depending on the level of training – highly trained athletes often have a shorter transition period between systems so the O2 system can contribute a greater % of energy

5000 metre run0-6 secs : CP system

6-30 secs : transition from PC to LA system

30 secs-2min. : predominantly LA system

2-5min. : Increased O2 supply, transition from LA to aerobic

5+ mins : predominantly O2 system provided intensity does not increase