Chapter 4

Foods, fuels and energy systems

Text Sources

1. Nelson Physical Education VCE Units 3&4: 4th Edition – Malpeli, Horton, Davey and Telford 2006.

2. Live It Up 2: 2nd Edition – Smyth, Brown, Judge, McCallum and Pritchard 2006.

The Importance of EnergyFoods, fuels and energy systems

The food is broken down into soluble chemicals (e.g. glucose) by digestion in the gut.

The soluble chemicals pass through the gut wall into the blood.

The blood carries the soluble food chemicals to all of the body’s cells, where they will be used for:

Energy

Growth Repair

Food is the source of energy for the human body and it also provides nutrients for growth and repair. When food is eaten, this is what happens…

Food for Exercise

The muscles of the body use both carbohydrates and fats to produce energy. The following diagram shows how carbohydrates are used.

Carbohydrates in the form of starch gained from foods such as pasta, bread and potatoes are eaten.

The starch is digested in the gut and turned into glucose molecules.

The glucose enters the small intestine where it passes intothe blood.

Here some of the glucose is stored as glycogen (100grams) and used to maintain blood sugar levels.

Glucose is stored here as glycogen (400grams) and is used when the body is working harder.

Glucose diffuses easily into the cells and is used to meet their energy demands.

Skeletal Muscle

LiverBody Cells

Food Fuels and ATP

Foods, fuels and energy systems

Food Fuels for Energy1. Carbohydrates (CHO) –

Preferred source of fuel during exercise (Glycogen)

2. Fat – Concentrated fuel used during rest and prolonged sub-maximal exercise.

3. Protein – Used for growth and repair (Negligible use during exercise)

See fig 4.2 p.86

p.87

Adenosine Triphosphate (ATP)

Our mechanical energy required for muscular contractions, require the chemical breakdown of the ATP molecule (Forms ADP).

Our ATP stores are very limited, therefore it must continually be rebuilt.

Nutrients assist in rejoining the split molecule

The Three Energy Systems

Foods, fuels and energy systems

Energy Systems

Which of the 3 systems that operate during exercise depends on a number of factors including;•Duration•Intensity•If oxygen is present•Urgency of energy required

Systems and their alternative names

• ATP-PC• Alactacid• Creatine Phosphate• Phosphogen system2. Lactic Acid (LA)• Anaerobic glycolysis• Lactacid3. Aerobic• Oxygen system• Aerobic glycolysis

Energy Systems

The ATP-PC systems and the Lactic Acid system are anaerobic, meaning they can work in the absence of oxygen.The Aerobic system, is aerobic, therefore requires the use of oxygen

During the start of exercise all three energy systems are in use. Their contribution is dependent on the intensity and duration of the exercise..........

Fuels at Rest

Foods, fuels and energy systems

Food Fuels at RestRest (Aerobic)• Fat and glucose are

the preferred fuelsDuring Exercise1. Short duration /

high intensity – Anaerobic systems used using carbohydrates.

2. Long duration / low intensity – Aerobic system using carbohydrates. However, fats are used once glycogen stores are depleted.

Contributions of Carbohydrates, fats and Protein to Energy ProductionFoods, fuels and energy systems

Energy Demands - Intensity

Low intensity•ATP requirements are met aerobically using the aerobic system.High Intensity•Explosive movements require instant supply of ATP which can’t be met aerobically, therefore the ATP-PC and lactic acid systems need to be used anaerobically.

                                           

Aerobic

Anaerobic

Carbohydrate Contributions

Storage (Based on 80kg person)•Muscle glycogen – 400g•Liver glycogen – 100g•(enough to fuel a 25km run!!!)

Intake of Carbohydrates depends on the intensity and duration of exercise bouts.•Normal contribution to diet is 55-60% CHO•Carbohydrate loading (80% CHO intake) is used to endurance activities.

Carbohydrate rich diet;•Increases glycogen stores•Glycogen is used in rebuilding ATP

CHO preferred fuel over fats during exercise due to requiring less oxygen to release energy.

Athletes need to be aware of their dietary intakes of CHO.

Excess CHO is converted to adipose tissue (Fat).

Fat Contributions

Storage of fats•Adipose tissue•Triglycerides (Broken down into free fatty acids which in turn are broken down to provide energy)Aerobic metabolism of fat is;•Slow•Requires more oxygen•Adds stress to the oxygen transport system•ATP yield is much higher from fat (460 molecules) in comparison to glucose (36).

At rest•50% of energy supplied by fats•Oxygen demand is easily met to burn fats

Benefits of fat•Large energy store•Transport medium for fat soluble vitamins A,D,E & K

Negative aspects of fat•Adverse health effects•Obesity, heart disease etc.

Protein Contributions

Role of protein (Amino acids) in the body;

• Growth and repair• Speed up reactions in

the body (Enzymes)• Produces hormones and

antibodies

Protein and exercise1. Not used as a fuel,

therefore low priority.2. Only used in extreme

circumstances3. Normal diet contains

enough protein (15%).Excess protein can lead to;• Less intake of CHO• Increase in fat intake

from animal products• Increase in fluid waste

Prolonged Endurance EventsDuring prolonged endurance events such as marathon running and triathlons;•Body uses a combination of CHO and fats.•Trained athletes are able to ‘spare’ glycogen and use free fatty acids (this is know as glycogen sparing).•Fats cannot be used alone as a fuel (poor solubility in the blood - hydrophobic).•‘Hitting the wall’ occurs when glycogen stores are depleted. This is called ‘hypoglycaemia’.•This is why athletes consume Gatorade, Glucose supplements etc...

p.92

Glycemic Index (GI)

Glycemic index;•Rating of CHO effect on blood glucose•Quick breakdown with immediate effect on blood glucose levels are labelled high GI •Slow breakdown are labelled low GI

Before exercise you should eat;

•Food that maintains blood glucose levels ie.low GI food

•Avoid high GI food eg lollies prior to exercise (can impair CNS function and accelerate glycogen depletion).

•High GI cause an insulin surge, effecting the performance of an athlete

p.94

The ATP-PC System

Foods, fuels and energy systems

The ATP-PC System

•Quickest system•Dominant system for the first 10-15 seconds of high intensity exercise•Used in fast, powerful movements.•Examples................???

•Breaks down phosphocreatine (PC) to form ATP anaerobically.•However, PC stores require time to replenish.

*** Read Summary of the ATP-PC system pg 96 of TEXT

How does the system work?•PC releases a free phosphate molecule

PC = P + C ADP + P = ATP

•Body has a larger storage of PC compared to ATP (4 times as much in the muscles)•PC stores can be replenished through aerobic recovery.•Once PC stores are depleted, they body must use glycogen through the anaerobic pathway.

The Lactic Acid System

Foods, fuels and energy systems

The Lactic Acid System

The lactic acid system;

•Activated at the start of intense exercise

•More complex reactions than the ATP-PC system

•Peak power until it fatigues (2-3 minutes)

•Predominant energy supplier in events 85% max HR eg. 200m sprint.

How the system works;•Glycogen is broken down in the absence of oxygen (Anaerobic glycolysis)•This produces a fatigue causing by product called lactic acid.•Lactic acid makes the muscle pH decrease (More acidic), reducing ATP resynthesis.The lactic acid system;•Provides twice as much energy for ATP resynthesis than the ATP-PC system.•Experiences problems at the anaerobic threshold.

Data analysis 4.1 p.99-100

Anaerobic respiration involves the release of a little energy, very quickly from the incomplete breakdown of glucose without using oxygen, inside the cells.1. Glucose is made available by the breakdown of glycogen

stored in the working muscles.2. The glucose is used by the muscles of the body to produce

energy, without the use of oxygen.3. This process creates lactic acid, which passes back into the

blood for removal.

Anaerobic Respiration Anaerobic Respiration

The Process of Anaerobic Respiration

Glucose

Energy for muscles to contractand create movement

Lactic Acid

Glucose is transported to the muscles of the body via the blood.

How Anaerobic Respiration Happens

How Anaerobic Respiration Happens

Glucose passes into the muscles cells and is used to produce energy for muscularcontractions.

Anaerobic respirationproduces lactic acidas a waste product.

Facts about Anaerobic Respiration

During anaerobic respiration, your muscles are not supplied with enough oxygen.

The lactic acid builds up due to the shortage of oxygen. This is known as an oxygen debt, which needs to be paid back once exercising has finished.

The lactic acid build-up will soon make your muscles feel tired and painful, so exercising anaerobically can only be carried out forshort periods of time.

READ Summary of Lactic Acid system pg.98

1 2 3

Anaerobic Respiration is how sprinters produce the energy that is used in short periods of ‘all out effort’ - high intensity.

Glucose produces…

Lactic acid quickly builds up

& makes the muscles feel

tired & painful. ‘All out effort’ cannot last for

very long!

The rest is converted into

heat to warm the body.

Oxygen cannot reach the muscles fast enough, so anaerobic respiration is used.

Some is used formuscle

contractions,creating

movement.

Lactate Inflection Point (LIP)

• LIP is a term which is used to describe the relationship between the entry and removal of lactate in the blood stream

• it has been created to replace the several terms which have come to dominate the area of physical education which can confuse the actual definition of Anaerobic Threshold

• activity levels above the LIP are associated with fatigue and an increase of lactic acid within the body

• The greater the intensity above the LIP the faster the fatigue will set in

• The LIP can also help predict the speed and power a person can sustain and for how long

There are only a few methods that can test

for the LIP and they are either through

blood tests or ventilation

The Aerobic System

Foods, fuels and energy systems

The Aerobic System

The aerobic system•Slowest contributor to ATP resynthesis•However, produces much more energy than the anaerobic systems•Becomes major contributor once the lactic system decreases.•Major contributor in prolonged exercise eg. Endurance events.•Aerobic system does contribute in maximal intensity exercise (Eg. Between 55-65% in 800m)See table 4.4 p.101 and 4.5 p.102

How the system works (aerobic glycolysis);

1st STAGE: CHOs andTryglycerides (FFA + glycerol) broken down to release energy. This produces pyruvic acid. Energy is released

2nd STAGE: Pyruvic acid is further broken down producing carbon dioxide (Kreb’s cycle)

3rd STAGE: Further breakdown via the electron transport chain. It requires hydrogen ions and oxygen, producing water and heat.

1. Glucose and oxygen are transported to the working muscles bythe blood.

Aerobic respiration involves the release of energy from the slow breakdown of glucose using oxygen, inside the cells.

2. Glucose and oxygen are then used by the muscles of the body to produce energy.

3. This process creates carbon dioxide and water.4. The carbon dioxide passes back into the blood for removal.

The Process of Aerobic Respiration

Energy for Musclesto contract and

create Movement

Water

CarbonDioxide

Glucose

Oxygen

Facts about Aerobic Respiration

How Aerobic Respiration Happens…

How Aerobic Respiration Happens…

Glucose and oxygen are carried by the haemoglobin in the red blood cells.

Glucose and oxygen pass into all the muscle cells of the body and is used to help produce energy for muscular contractions.

Aerobic respiration produces carbon dioxide & water as waste products.

During aerobic respiration, the heart and lungs supply the muscles with plenty of oxygen.

The carbon dioxide is breathed out via the lungs, while the water is lost as sweat, urine or in the air we breathe out as water vapour.

As long as the muscles are supplied with enough oxygen, exercising aerobically can be carried out for a long period of time.

READ Summary of Aerobic System pg. 104

1 2 3

Aerobic respiration is how marathon runners produce the energy that is used in long periods of less intensive effort.

Glucose and oxygen produce…

Carbon dioxide, which is carriedaway by the blood& excreted through the lungs.

Water, which is carried away by the blood and excreted through the lungs, sweat and urine.

Some is used formuscle contractions,creating movement.

The rest is converted into heat to warmthe body.

Energy and Types of Physical Activities

Energy and Types of Physical Activities

Each physical activity or sport you undertake requires a different energy system…

Track Events and their use of Aerobic Respiration

Basketball players use both systems

Some use mainly aerobic respiration.

Others use mainly anaerobic respiration.

Most use a combination of the two.

EventPercentage of

Aerobic Respiration

Less than 1%100 m

10%200 m

20%400 m

50%800 m

60%1,500 m

83%5,000 m

95%10,000 m

100%Marathon

Energy System Interplay

Foods, fuels and energy systems

Interplay Between Energy Systems

All activities use some energy from all three systems.The energy systems overlap – they never work independently.It it’s the relative contribution of each system that varies.

Interplay – Game of Netball / Basketball

Which energy systems are at use as you play a game of basketball or netball?????

Read bottom of page 108-109

Duration and Intensity

Duration of event Intensity of event Primary energy system(s)

0-6 seconds very intense ATP-PC

6-30 seconds intense ATP-PC and Lactic Acid

30 sec. - 2 minutes heavy Lactic Acid

2-3 minutes moderate Lactic Acid and Aerobic

> 3 minutes light Aerobic

Comparing the Three Energy SystemsFoods, fuels and energy systems

Comparing the Energy Systems and Interplay

Energy Production•ATP-PC – 5.7 to 6.9 kcal•Lactic Acid – 10 to 12 kcal•Aerobic – 980kcal

See table 4.6 p.107

Note 10kcal = 1 mole

High Intensity Competition

Web Links – Chapter 4•Australian Sports Commission: http://www.ausport.gov.au •Find 30 promotion (Government of WA Department of Health): http://www.find30.com.au •Walking School Bus promotion (UK): http://www.walkingbus.com •Ministry of Health (New Zealand) toolkits: http://www.newhealth.govt.nz •The 10,000 Steps Rockhampton project: http://www.10000steps.org.au/rockhampton/ •Travelsmart Australia: http://www.travelsmart.gov.au •World Health Organisation: http://www.who.int •Heart Foundation Australia: http://www.heartfoundation.com.au •VicHealth (The Victorian Health Promotion Foundation): http://www.vichealth.vic.gov.au •Be Active promotion (Government of South Australia): http://www.beactive.com.au •Go For Your Life: http://www.goforyourlife.vic.gov.au •Physical Activity Resources for Health Professionals – Introduction (Centre for disease control and prevention – USA): http://www.cdc.gov/nccdphp/dnpa/physical/health_professionals/index.htm •Health Promotion (Public Health Agency of Canada): http://www.phac-aspc.gc.ca/hp-ps/index.html •Strategic Inter-Governmental Forum on Physical Activity and Health (SIGPAH): http://www.nphp.gov.au/workprog/sigpah/ •Healthy youth (Centre for disease control and prevention (USA): http://www.cdc.gov/HealthyYouth/ •America On The Move promotion: http://www.americaonthemove.org •Papers from the International Journal of Behavioural Nutrition and Physical Activity: http://www.ijbnpa.org/home •Department of health and aging (Australian government): http://www.health.gov.au/internet/wcms/publishing.nsf/content/home •Building a healthy, active Australia (Australian government): http://www.healthyactive.gov.au •National Public Health Partnership: http://www.nphp.gov.au •Be Active promotion (Government of South Australia): http://www.beactive.com.au •Sport and Recreation Australia: http://www.sport.vic.gov.au

•VCE Board of Studies – additional information about energy systems: http://vcaa.vic.edu.au/vce/studies/physicaledu/EnrgSys.pdf •Heart Foundation Australia: http://www.heartfoundation.com.au •Australian Institute of Sport – sports nutrition: http://www.ais.org.au/nutrition/ •Nutrition Australia: http://www.nutritionaustralia.org/ •Dietician's Association of Australia: http://www.daa.asn.au/ •Sports Coach UK – energy pathways: http://www.brianmac.demon.co.uk/energy.htm •‘How stuff works’ – How exercise works: http://health.howstuffworks.com/sports-physiology6.htm

• Info about the glycemic index: http://www.glycemicindex.com/