Energy Systems

©Subject Support 2010.

Learning Objectives

To understand the different energy systems

To understand each energy systems use in sport and exercise

REMEMBEREnergy can be defined as the

capacity to do work!

Grading Criteria

P7 – Describe the three different energy systems and their use in sport and exercise activities

M4 – Explain the three different energy systems and their use in sport and exercise activities

D2 – Analyse the three different energy systems and their use in sport and exercise activities

Unit Content

Energy systems – Phosphocreatine; Lactic Acid; Aerobic energy system

Amount of ATP produced by each systems

Sports that use these systems to provide energy

Recovery time

Energy Systems

©Subject Support 2010.

• ATP-PC System (anaerobic)

• Lactic Acid System (anaerobic)

• Aerobic Energy System

Energy Systems

The use of each system depends on the intensity and duration of each activity:If the activity is short in duration (less than

10 seconds) and high intensity, we use the ATP-PC system

If the activity is longer than 10 seconds and up to 3 minutes at high intensity, we use the lactic acid system

If the activity is long in duration and submaximal pace, we use the aerobic system

Energy Continuum

Sometimes we need to use all three systems to regenerate ATP because the demands of an activity are varied. For example, in rugby:A short sprint to tackle a player uses the ATP-

PC systemA long sprint the length of the pitch to score

a try uses the lactic acid systemPositional play will use the anaerobic system

Adenosine Triphosphate (ATP)

ATP is vital for muscle contraction it is the only form of useable energy in the body

The body only has enough ATP stored for 1 explosive act (about 3 seconds)

After that there is none leftThen energy has to be created by other

means

ATP (1 explosive act) = ADP (adenosine phosphate)

ADENOSINE PHOSPHATE PHOSPHATE PHOSPHATE

High energy bond

ADENOSINE PHOSPHATE PHOSPHATE

PHOSPHATE

ENERGY

ATP – Adenosine TriPhosphate

ADP – Adenosine DiPhosphate

Phosphocreatine Energy System (ATP/PCr System)

ADP + Creatine Phosphate (PCr) = ATPLasts about 10 secondsHigh intensity maximum workExtremely efficientDoes not need oxygenHas no waste products

Think 100 meters

ATP-PC SystemAdvantages

Phosphocreatine stores can be regenerated quickly (50% replenishment in 30 s; 100% in 3 mins)

No fatiguing by-products Creatine supplementation extends the time that the ATP–

PC system can be utilisedDisadvantages

There is a limited supply of phosphocreatine in the muscle cells, i.e. it can only last for 10 s

Only 1 molecule of ATP can be regenerated for every molecule of PC

PC regeneration can only take place in the presence of oxygen (i.e. when the intensity of the exercise is reduced)

Lactic Acid Energy System

ADP + Glucose = ATPWhen PCr runs out, the muscles call

upon stores of glucose (glycogen).Lasts between 10-60 seconds.Has a waste product called pyruvic acidIf not enough oxygen is breathed in to

break pyruvic acid down (oxygen debt) it converts into lactic acid

This is also called anaerobic glycolysis

Think 400m

Lactic Acid Energy System

Carbohydrate in Food

Glucose in bloodstream

Glycogen in Liver

Glucose in Muscle

Glycolysis2 ATP

Pyruvic Acid

Lactic Acid (1) Lactic Acid (1)

AN

AE

RO

BIC

Mus

cle

Sar

copl

asm

Acetyl Coenzyme A

+ O2

Lactic Acid System

AdvantagesATP can be regenerated quite quickly because few chemical reactions are involved.In the presence of oxygen, lactic acid can be converted back into liver glycogen, or used as a fuel by oxidation into carbon dioxide and water.It can be used for a sprint finish (i.e. to produce an extra burst of energy).

Lactic Acid SystemDisadvantages

Lactic acid is the by-product! The accumulation of acid in the body denatures enzymes and prevents them increasing the rate at which chemical reactions take place.Only a small amount of energy (5%) can be released from glycogen under anaerobic conditions (as opposed to 95% under aerobic conditions).

Aerobic Energy System

Starts similar to the Lactic Acid systemADP + P + Glucose = ATP + Pyruvic AcidAs oxygen is present the pyruvic acid

does not convert into lactic acid but into another 34 molecules of ATP

Long term low intensity exerciseCarbon dioxide (CO2) and water (H2O0

are waste products of this systemThink long distance running

Aerobic Energy System

The aerobic system of energy production needs oxygen.

Breaks down carbohydrates & fats into CO2, H20 and ENERGY

Takes approx 3 mins to extract 95% of energy from glucose molecule

This supplies the body with a prolonged and steady supply of energy.

O2

Aerobic Energy System

Immediate energy production, therefore comes from the other two anaerobic systems used.

Heart rate and ventilation rate increase during exercise. The vascular system distributes more oxygenated blood to our working muscles.

Within 1-2 mins the muscles are being supplied with enough oxygen to allow effective aerobic respiration

ATP (1 burst of energy) =ADP

ADP+ PCr = ATP (3-10s of work) = ADP

ADP + Glucose= ATP (10-60s of work) = ADP + Pyruvic Acid

(No oxygen = lactic acid)

ADP + P + Glucose = ADP + Pyruvic Acid

+ Oxygen =34 ATP + CO2 + H20

AE

RO

BIC

Mus

cle

Mito

chon

dria

Pyruvic Acid

Glycolysis 2 ATP

Acetyl CoA

Citric

Acid

+ Oxaloacetic Acid

AN

AE

RO

BIC

Mu

scle

Sa

rco

pla

sm

Krebs Cycle

2 ATP

Carbon Dioxide

Hydrogen

Electron Transport Chain

O2

Electron Transport Chain

The Aerobic System

Advantages More ATP can be produced — 38 ATP from the

complete breakdown of one glucose molecule. There are no fatiguing by-products (only carbon

dioxide and water). Stores of of glycogen and triglyceride are

plentiful, so exercise can last for a long time.

The Aerobic System

Disadvantages This is a complicated system so it cannot be used

immediately. It takes time for enough oxygen to become available to meet the demands of the activity and ensure glycogen and fatty acids are completely broken down.

Fatty acid transportation to muscles is low and fatty acids require 15% more oxygen to break them down than glycogen.

Food Fuels

Food is the basic form of energy for ATP regeneration. The main energy foods are: carbohydrates — stored as glycogen and

converted into glucose during exercise glycogen — a complex sugar supplied from

muscle or liver stores glucose — a simple sugar supplied from the blood fats — stored as triglycerides in adipose tissue

under the skin and converted by the enzyme lipase to free fatty acids when required

When are These Fuels Used During Exercise?

The intensity and duration of exercise play a huge a role in determining whether fats or carbohydrates are used.

The breakdown of fats to free fatty acids requires more oxygen than that required to breakdown glycogen. It is also a much slower process.

Therefore, during high-intensity exercise when oxygen is in limited supply, glycogen will be the preferred source of energy.