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بسم الله الرحمن الرحيمبسم الله الرحمن الرحيم

Gad El-Mawla Abd El-AzizProfessor of PhysiologyMansoura University

M.B., B.Ch. 1974 Mansoura University, Egypt.

M.Sc. (Physiology) 1980.

PhD. (Physiology) 1984.

Professor of Physiology (1994).

E-mail: elmawla@hotmail.com

Sources of energy During rest and Exercises

Energy: is the capacity to perform work

Cells in the body need energy to function

FOOD = ENERGY (E)

Cells don’t get Energy directly from food, it must be broken down into: ATP - Adenosine Triphosphate

ATP: The energy “currency” of the cells.

ATP :

ATP : is a high energy compound stored in our cells and is the source of all energy used at rest and during exercise.

Energy in food is released within the

cells then stored in the form of ATP.

Formation of ATP provides the cells

with a high-energy compound for storing

energy.

Nutrients which give us energy:

Carbohydrates

Fats

Proteins

DigestionGlucose

Fatty acids

Amino Acids

Fats

Carbohydrates

Protein

Common Pathway Energy

These nutrients are absorbed into the blood & transported to cells (muscle, liver & nerve).

They are used to produce ATP or stored.

ATP is stored in small amounts, therefore the rest is stored as:

Glucose = Glycogen (muscle & liver).

Fatty Acids = Body fat.

Amino Acids = Growth, repair or excreted as waste.

Carbohydrate: (Body’s primary energy source for most activities)Body’s primary energy source for most activities)

 

Carbohydrate: Readily available and easily metabolized by

muscles.

It is transported as glucose and taken up by

muscles and liver and converted to glycogen.

Glycogen stored in the liver is converted back to

glucose as needed and transported by the blood to

the muscles where it is used to form ATP.

Glycogen stores are limited.  

Fat : Provides energy at rest and during

prolonged, low-intensity activity. Body stores of fat are larger than

carbohydrate reserves.  

Fat : Less accessible for metabolism because it must be reduced to glycerol and FFA. FFAs are used to form ATP. Trained muscle has a greater ability to use fat as fuel. As exercise is prolonged, fat becomes the main fuel. Requires more oxygen for aerobic breakdown.

Protein: Can only supply up to 5% to 10% of the energy needed to sustain prolonged exercise. Amino acids are broken down into glucose (gluconeogenesis).

Protein : A gram of protein yields about 4 Kcal. Can be used as an energy source if

converted to glucose via gluconeogenesis. Only basic units of protein (amino acids) can

be sued for energy.

Sources of Energy during & after exercises

Energy Systems:

Three basic energy systems:

1. Phosphagen energy system:

(Immediate energy system).

2. Anaerobic or glycolysis energy system:

(Glycolytic or non-oxidative system).

3. Aerobic or Oxidative energy system:

(Mitochondrial respiration )

I- Phosphagen energy system

It is utilized during transition from rest to exercise, and also during the transition from one exercise intensity to a higher intensity.  It does not need oxygen. It leaves no waste products.

I- Phosphagen energy system

During a contraction: Myosin cross-bridge breaks down ATP,

producing ADP and a phosphate group. Creatine phosphate is then used to

"recharge" ADP, converting it back to ATP : ADP + creatine phosphate ADP + creatine phosphate ATP + creatine. ATP + creatine.

ATP ATP ADP+ P (phosphoric acid) + energy ADP+ P (phosphoric acid) + energy

The Phosphagen system is active during all-out

exercise that lasts about 5 to 10 seconds, such

as a 100-meter dash, lifting a heavy weight, or

any other activity that involves a maximum, short

burst of power.

This system relies on stored ATP and to a larger

extent, creatine phosphate, to provide immediate

energy.

For any exercise lasting longer than 10

seconds, assistance from other systems is

required.

II- Anaerobic or glycolysis energy system

Breakdown of glucose into pyruvic acid in the sarcoplasm of the muscle.

Pyruvic acid produced is converted into lactic acid which diffuses out of the muscle and accumulate in the blood.

When the muscle is doing work at faster rate, more than the blood can supply O2 and nutrients, the muscle depends on local glycogen stores and anaerobic glycolysis.

Glucose ( muscle glycogen )

Anaerobic oxidation

2 pyruvic acid + 2 ATP

II- Anaerobic or glycolysis energy system

The advantage: it is able to supply ATP at

a high rate and within a short time.

The disadvantage: it provides only 2 ATP

molecules from each molecule of glucose. So,

anaerobic glycolysis is rapid but not

economic.

o Anaerobic glycolysis supplies the total energy requirements for moderate to high intensity exercise lasting about one to two minutes.

o Anaerobic Glycolysis continues to supply energy during exercise lasting up to ten minutes.

o This system breaks down muscle and liver glycogen stores without the use of oxygen. 

Micheal Gohnson 200 meter run

Production of ATP by anaerobic glycolysis is

not as fast as Phosphagen system, which makes muscle contraction slower.

When oxygen is not available the lactic acid, produced causes rapid muscle fatigue.

Anaerobic glycolysis supplies ATP at high rate and within short time but it is not economic.

Anaerobic glycolysis

Glucose Produces

Oxygen cannot reach the muscles fast enough.

Glucose produces

Lactic acid is formed quickly which makes muscles feel tired & painful.

Part is used for muscle contractions, creating movement.

Anaerobic glycolysis

Oxygen cannot reach the muscles fast enough.

Glucose produces

The rest is converted into heat.

Lactic acid is formed quickly which makes muscles feel tired & painful.

Part is used for muscle contractions, creating movement.

Anaerobic glycolysis

Oxygen cannot reach the muscles fast enough.

Anaerobic glycolysis

In Anaerobic glycolysis lactic acid accumulate in In Anaerobic glycolysis lactic acid accumulate in blood and fatigue occurs earlyblood and fatigue occurs early

Function of lactic acidFunction of lactic acid

It stimulates respiratory and It stimulates respiratory and

circulatory systems to increase their circulatory systems to increase their

activities.activities.

It is converted to glucose in the liver.It is converted to glucose in the liver.

Lactic acid is the preferable fuel to Lactic acid is the preferable fuel to

the heart.the heart.

Function of lactic acid: Function of lactic acid:

In the muscles it causes capillary In the muscles it causes capillary dilation and dilation and blood flow. blood flow. It causes shift of OIt causes shift of O22 dissociation dissociation curve to right i.e. giving Ocurve to right i.e. giving O22 easily to easily to active muscles.active muscles. It is oxidized in the recovery period It is oxidized in the recovery period to replenish ATP and energy stores. to replenish ATP and energy stores.

Aerobic or Oxidative energy system:

It is used during lower levels of activity (as in marathon) when there is enough energy being delivered to the working muscles.

Depends on O2 for break down of fuels to energy. Produces ATP in mitochondria of cells. Can yield much more energy (ATP) than anaerobic systems.

It is used for energy production during

endurance events ( economic).

As a rule, the more intense the activity,

the more glucose is used instead of FAT.

At lower levels of activity fats can be

used as muscle fuel.

During exercise, VO2 rises rapidly until

“steady rate”.

Aerobic oxidation of CHT and fat produce

ATP, CO2, H2O, and heat.

CO2 is transported to lungs while heat

and water are released through sweat.

Provides energy for 2 minutes to 3 hours

of work.

Supply ATP slowly to the active muscles.

Relative rates of ATP utilized by aerobic, anaerobic and Phosphagen systems

Aerobic systemAerobic system 1.0 M of ATP / min. 1.0 M of ATP / min.

AnaerobicAnaerobic systemsystem 2.5 M ATP / min. 2.5 M ATP / min.

PhosphagenPhosphagen systemsystem 4.0 M ATP / min. 4.0 M ATP / min.

Comparing the 3 energy systems for endurance:

PhosphagenPhosphagen systemsystem 10 – 15 sec. 10 – 15 sec.

AnaerobicAnaerobic systemsystem 30 – 40 sec. 30 – 40 sec.

AerobicAerobic systemsystem unlimited time (as unlimited time (as

long as nutrients last)long as nutrients last)

Energy systems used in Energy systems used in sports:sports: Phosphagen system:Phosphagen system: 100 meter dash, 100 meter dash,

jumping, weight lifting, and diving.jumping, weight lifting, and diving. Phosphagen and anaerobic systems:Phosphagen and anaerobic systems: 200 200

meter dash.meter dash. AnaerobicAnaerobic systemsystem mainly:mainly: 400 meter dash, 400 meter dash,

100 meter swim, 800 – 1,500 meter dash, 100 meter swim, 800 – 1,500 meter dash, 200 – 400 meter swim, and boxing.200 – 400 meter swim, and boxing.

AerobicAerobic system:system: 10,000 meter skating, 10,000 meter skating, marathon run, and Jogging ( 42.2 Km.) marathon run, and Jogging ( 42.2 Km.)

Blood gulcose+ 6o2

Aerobic oxidation 6co2 +6H2O + 38ATP

Keb’s cycle

Oxidation of Carbohydrate: Pyruvic acid from glycolysis is converted

to acetyl CoA.

Acetyl CoA enters the Krebs cycle and forms ATP, carbon dioxide, and hydrogen.

One molecule of glucose can generate up to 38 molecules of ATP.

 

Free fatty acid +O2 Aerobic oxidation

CO2 +H2O + ATP

Oxidation of Fat : Lypolysis – breakdown of triglycerides into glycerol and free fatty acids (FFA’s). FFA’s are broken down in the mitochondria into acetyl CoA. Acetyl CoA enters the Krebs cycle for oxidation. Fat oxidation requires more oxygen and generates more energy than carbohydrate oxidation.  

Aerobic oxidation

In Aerobic glycolysis fatigue is delayedIn Aerobic glycolysis fatigue is delayed

Aerobic oxidation

Glucose and O2 produce

Glucose and O2 produce

Some is used formuscle contractions,creating movement.

Aerobic oxidation

Glucose and O2 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.

Aerobic oxidation

Oxygen DebtOxygen Debt

Oxygen DebtOxygen DebtOxygen DebtOxygen Debt

It is the difference between oxygen needed by the contracting muscle and the oxygen available by the cardiovascular and respiratory systems.

O2 debt is paid at the end of

the exercise. Sprinters will

continue to breath more

deeply and rapidly for

minutes. This will enable

them to pay back the oxygen

debt, and allow lactic acid

levels to fall.

Oxygen DebtOxygen DebtOxygen DebtOxygen DebtMeasurement of oxygen debt :O2 debt: O2 consumption during recovery – O2 consumption during similar period of rest.

Importance of oxygen debt:

It helps the muscle to do an

exercise which is much greater

than would be possible if they

depend completely on energy from

oxygen consumption.

In exhausted muscles: There is an emergency metabolism for the supply of ATP.

This is done by combining two ADP molecules to reform one ATP molecule, and one AMP molecule.

ADP + ADP ATP + AMP

Metabolic changes During Recovery

At the end of the muscle activity ,the energy stores in

the muscle are depleted , and lactic acid is increased in blood .

Recovery occurs by removal of the lactic acid and regeneration of the energy stores.

A) Part of lactic acid is oxidized into CO2 and H2O. The energy produced from this oxidation is used for reformation of ATP and by turn Cr-p.

Metabolic changes During Recovery

Lactic acid oxidation

Pyruvic acidOxidation

Kreb’s cycleCO2+H2O+ATP

ATP + creatine Cr-P + ADP

B) The other part of the lactic acid diffuses to the blood stream and then to the liver where it’s converted into blood glucose. Muscles take glucose from the blood stream and changes it into muscle glycogen.

At the end of recovery , the energy stores in the muscle (ATP, Cr-P, and muscle glycogen ) are reformed again and the lactic acid is removed.

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