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USA Track and Field Level II Coaching Education

Part 1: The Energy Systems

Opening screen: Energy provides both machines and humans with the capacity to perform work. Without energy this conveyer belt will not

run. This machine is designed to convert oil into heat that is then used to

drive the conveyer belt so that the boxes can move from one location to

another. Like a machine the human body converts fuel sources that are in

the form of fats, proteins and carbohydrates - into a chemical energy

called adenosine triphosphate or ATP that is then used by the muscle cell

so it can contract and produce movement. In the process of making ATP,

heat is also generated as a byproduct, but heat is not a useful form of

energy for us. Indeed, heat can impair human performance and the body

works very hard to eliminate excessive heat that could interfere with the

activities of the cells.

Click the Start Button: Play the video clip. The sun is the initial source of our energy. Plants convert sun energy into

carbohydrates, fats and protein. Animals, including us eat those plants

and we also eat the animals. We have a processing plant called the

digestive system thats uniquely designed to convert food from the

environment into fuel that the body can use to produce ATP. Food we

eat moves down the esophagus and into the stomach where processing

begins. It then moves on into the small intestine where its converted

into the type of fuel the body can use amino acids, glucose and fatty

acids, which are then absorbed into the bloodstream and transported

into the cells where ATP is synthesized.

Go to the next screen: Adenosine triphosphate or ATP fuels the activities of most cells including muscle contraction, protein synthesis,

cell division and nerve signal transmission. In the graphic

representation of an ATP molecule on the screen there are three

phosphate groups that are shown in yellow. ATPs chemical energy is

stored in the phosphate bonds. All the energy stored in the food that

we eat must be converted into ATP before the cell can use it.

Go to the next screen: Five physiological systems are particularly important to the ability of the body to synthesize ATP. These include

three energy systems that synthesize ATP which we will overview in

Part 1; the cardiovascular and respiratory systems transport oxygen and

fuels to the cells where ATP production occurs. We overview these

systems in Part 2; Finally, the muscular and neurological systems use

the ATP to cause and coordinate movement - we overview these

systems in Part 3. While we will discuss each system separately the

cyclist shown on the screen demonstrates their functional integration.

An electrode has been placed over the vastus lateralis muscle of the

cyclist so we can see this muscle firing. When a muscle is working like

this it is requiring a large amount of ATP energy.

The body cannot supply this energy to any extent without oxygen. The gears represent the interdependence of the muscle

cells demand for oxygen with the response of the heart, lungs and blood vessels so that the exact amount of oxygen is

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supplied to the muscle cell. The job of the lungs is to bring oxygen from the atmosphere into close contact with the blood

vessels where a specially designed pump the heart - then transports the oxygen and other fuels through the blood vessels to

the working muscles.

The movie clip at the bottom left of your screen is showing oxygen being used in a muscle cell so that the energy needed by

that cell can be produced. Carbon dioxide, which is a waste product, is being sent out of the cell and will be transported back

to the lungs and then to the atmosphere. The important point is that the muscle cells energy demand sets the speed of oxygen

extraction from the atmosphere and its delivery to the working muscle. The neurological system is busy communicating

information throughout the body so that everything functions effectively. As a coach you need to understand the interactions

between these systems and how training alters their efficiency. If you know whats going on physiologically you will easily

be able to determine the frequency, duration and intensity of the training program that will optimize the performance of your

athletes.

Go to the next screen: This is the module index screen. You can navigate anywhere in the module by clicking the buttons on this screen.

Click the Goals button: Heres what you will know after you have completed this module.

Click the Home Button

Click the ATP stores and Energy Systems that remake

ATP button: Weve only got about 85 grams of ATP stored in our body. Thats a pretty limited store of ATP enough for a couple of

seconds of work. A single muscle cell can have up to 100 million

molecules of ATP in it so you can see that we are talking about very

tiny molecules. This store of ATP supply permits immediate muscular

response.

Each ATP contains a lot of energy, but the only way we can access that

energy is to break away one of those phosphate molecules. When the

phosphate breaks off that releases the energy our muscles use to move.

When a phosphate is broken off the ATP its broken down into

adenosine diphospate or ADP and there is a free phosphate, and of

course, there is the energy. The cell vehemently defends its ATP store. As soon as it is broken down into ADP and free

Phosphate the energy systems responsible for making ATP kick into action.

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Go to the next screen: If we couldnt remake ATP after a couple of seconds of work we would completely run out of it. Fortunately, we

have three ways to resynthesize ATP these are called energy systems

and they are presented here. The first is the Anaerobic Phosphagen

energy system - also known as the alactic system because there is no

lactate or lactic acid made from this energy system. The second in the

glycolytic energy system is also known as the anaerobic lactate

system. The third is the aerobic energy system.

Click on the Anaerobic Phosphagen energy

system button: Remember that energy systems are all about making ATP and the first system that does this is

known as the Anaerobic Phosphagen energy system. It is also

called the alactic system because no lactic acid is produced

and to confuse you further it is also referred to as anaerobic

because no oxygen is used in any way. This system is also

commonly referred to as the phosphocreatine energy system

and this is the term I prefer to use. Muscle cells have a store

of creatine phosphate that is a very high-energy molecule. As

this chap is doing his pull ups here, his muscles are using

ATP. If you remember ATP is broken down into adenosine

diphosphate and a free phosphate to release energy. That

energy is being used by the muscles to move. We are left

with ADP and a free phosphate. These ADPs will build up in

the muscle cell and after a couple of secs the level of stored ATP is vastly reduced. The phosphocreatine energy system is the

fastest energy system we have to remake ATP.

As the stored ATP is broken down into ADP and free phosphate, creatine phosphate releases its phosphate and an enzyme

called creatine kinase will attach it to an ADP to form ATP. This is a very fast and immediate mechanism to remake ATP

and can provide enough ATP for about 4 to 5 secs of additional maximum intensity work over and above the 1-2 secs

provided by the ATP stores after about 5 or 6 secs maximum power cannot be maintained because creatine phosphate stores

are running low. A 100-meter runner will start to slow down after about 60 meters. They are slowing down because they are

running short of creatine phosphate.

Go to the next screen: So in summary, the Phophocreatine energy system is a system that provides an

immediate way to remake ATP as the ATP stores are used up.

It is this system that is used when the athlete wants to perform

very high intensity activity demanding a lot of power.

However, its very short in duration. In conjunction with the

ATP stores the athlete only has about 5 to 7 seconds of ATP

supply.

The phosphocreatine system activates as soon as the athlete

begins using ATP above resting level. Creatine is a naturally

occurring amino acid thats found in meat and fish and our

body makes creatine in the liver, kidney and pancreas. About

98% of the creatine in the body is found in our muscle. If you

were a 70 Kg male you would store about 120 gms of creatine.

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Go to the next screen: We can challenge the phosphocreatine energy system with workouts of 7 to 10 secs of

high intensity work. Its important to train this system when

there is no fatigue present and it requires about 24 to 36 hours

of rest with low activity before doing another high intensity

speed workout. Allow about 90 secs between each rep so that

the creatine and phosphate can be reformed. Most athletes will

only be able to accumulate about 720 m of total work because

90 secs of rest only permits about 80% creatine phosphate

reformation. So you can see, during the second interval the

athlete has 20% less creatine phosphate available, and with

each rep after that there is less and less creatine phosphate. It is

pointless to do any more speed work after this because the

athlete will not be able to run fast enough to challenge this

system.

Go to the next screen: Here are some important summary points about the phosphocreatine or alactic energy system. It

does not appear to be a very trainable energy system although

there is some trainability. If you are measuring lactate levels

then you can obtain some idea as to how well the training has

challenged this energy system by looking at lactate levels after

a short all out effort. If there are low lactate levels then this

system is well developed. If not, then another energy system,

glycolysis that we will discuss next, is being used to make up

for the ATP shortfall. This is usually a good indication of either

a poor innate phosphocreatine energy system or a poorly

developed one.

Click the Return Button

Click the Anaerobic lactate (glycolytic) button: The fuel for the anaerobic glycolytic energy system is glucose.

We eat carbohydrate in the form of rice, pasta and potatoes.

Our digestion system processes this carbohydrate and breaks it

down to its simplest form, which is glucose. And then we

transport that glucose to the muscle and liver where it is stored

as glycogen. We can store about 500 grams of glycogen. Any

excess glucose that cannot be stored as glycogen is stored as

fat. Most of the fuel source for glycolysis starts from glycogen

although free glucose is also used when available. A series of

chemical reactions break down the glucose to pyruvate. These

chemical reactions are referred to as glycolysis. Lysis is just a

Greek word meaning to break down. So glycolysis simply

means to break down glucose. Enough energy is released from

glycolysis to resynthesize 2 ATP. Glycolysis occurs in the

cytoplasm of the cell and the process does not require oxygen, which is the reason this energy system is referred to as

anaerobic. The end product of glycolysis is pyruvate.

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Go to the next screen: Here we have a glucose molecule. Two ATP attach to the carbon chain of the glucose

molecule and donate a phosphate to make the glucose more

chemically reactive. So at this point the process has actually

used 2 ATP and produced 2ADP

As glycolysis continues the 6-carbon glucose molecule is

split into two three carbon compounds and this gives the

pathway its name.

In the next phase of glycolysis the initial ATP investment

pays dividends as each of the two 3 carbon compounds is

broken down into pyruvate a hydrogen ion carrier known as

NAD extract high energy electrons and hydrogen and carries

them off to the mitochondria where they will produce more

ATP and we will come back and talk more about this when

we discuss the aerobic system. This takes away some of the energy from the 3 carbon compounds.

Energy from the 3-carbon compounds is also used to synthesize ATP. An enzyme catalyzes the transfer of the phosphate

groups to ADP forming 2 molecules of ATP. This takes away more energy from the three-carbon compound. Now we have 4

ATP.

A final tally of ATP production shows that for 2 ATP expended 4 ATP are synthesized yielding a net of 2 ATP for each

molecule of glucose that is oxidized into pyruvate.

Go to the next screen: Pyruvate has two fates depending on how quickly ATP is being used. It can be

transported into the mitochondria where it participates in the

aerobic energy system. Or, it can be converted into lactic

acid. When the athlete is running at speeds that demand a rate

of ATP production the aerobic energy cannot cope with it.

Under these conditions glycolysis occurs at such a rapid rate

that the cell runs out of NAD. When this happens pyruvate

picks up hydrogen ions to form lactic acid, which is then

quickly converted to lactate and free hydrogen ions. When

the hydrogen ions begin to build up so does the cells acidity.

The lactate will diffuse into the adjacent muscle cell or be

diffused out into the blood and be carried off to other muscles

where it can be used as fuel for aerobic ATP production -

such as in the cardiac muscle. The hydrogen ions must be

buffered and the strength of the buffering system determines

how long the athlete can last at a fairly high speed.

Go to the next screen: More and more coaches are testing how much lactate builds up in the athletes blood

during different intensity of workouts with this information it

is possible to gage the strength of all three energy systems.

The test is easy to do because we now have portable

analyzers. Theres a relationship between the level of lactate

in the blood and fatigue because the amount of lactate in the

blood is related to the hydrogen ion content. Its that acidity

that causes fatigue not the lactate although very high lactate

content does appear to have some affect on the ability of the

cell to take up oxygen but this is beyond the scope of Level

II. The test we undertake is called the lactate threshold test.

Were interested in when lactate starts to rise above base

level. When it starts to rise its called the lactate threshold I

or aerobic threshold and some endurance coaches call it. Its

at this point that glycolyis is playing a bigger role to provide ATP. Another point of interest is the 4-mmol level of blood

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lactate. This is called the onset of blood lactate accumulation and for most athletes this is the point where glycolysis is being

very heavily used. These are just two of the many terms that are used to describe the rise in lactate in the blood. But any

further discussion is outside the scope of level II knowledge.

I just want to comment that the lactate threshold test is often done in conjunction with a VO2max test, which is a test for the

athletes aerobic capacity that we will talk about in a little bit. The VO2 max test tells us the ability of the athlete to take on

and use oxygen. If we equate an athlete with a car we can say that the VO2 max is the size of the athletes engine. The lactate

threshold test tells us when the engine starts to break down. So, you really need to know both pieces of information the size

of the engine and when the engine starts to break down.

Go to the next screen: Here are the important points about the anaerobic lactate system. The system does not

produce a very high quantity of ATP, but it is a very fast

system. It is not as fast as the alactic energy system, and its

not possible to produce the same amount of power, but it

does provide reasonable speed for races lasting 30 to 60

seconds of maximum effort. The fuel is glycogen or glucose.

Because the workouts challenging this system produce an

acidic environment the athlete is limited in the number of

times per week workouts stressing this system can be done.

Usually twice a week is about all most athletes can handle.

The acidic environment takes quite a toll on the muscle cell

membrane, enzymes and cellular transport mechanisms so

adequate rest is needed for the body to repair the damage

done.

Go to the next screen: There are 3 different ways to challenge the anaerobic lactate energy system. These are

referred to as speed endurance, special endurance 1 and

special endurance II. Your event instructors will discuss

when you use each type of workout. Basically, speed

endurance does not have a heavy lactate accumulation and is

usually used to train sprint motor patterns. Special endurance

1 helps with acid buffering capacity and special endurance II

challenges the acid buffering system and the neurological

system. Remember that whenever the athlete is using the

anaerobic lactate system there is a heavy usage of glycogen

stores and there is a heavy acid penalty.

Go to the next screen: Heres a summary of what we have discussed so far. Anaerobic glycolysis supplies 4 times more

ATP than the phosphocreatine system but there is a lower

power output and a lactic acid penalty. As you watch the video

you should now be able to point out which activity relies on

phosphocreatine and which relies on glycolysis. Both the ATP

PC energy supplies and the lactic acid energy supplies are

anaerobic because they do not require oxygen. ATP store usage

and the phosphocreatine energy system are both alactic because

no lactic acid is produced. This is the energy used when high

power is needed. The glycolytic energy system provides a

reasonable amount of power that lasts much longer than the

ATP-PC energy supplies. The problem is the acid by-product

that eventually interferes with the ability of the cells to

function.

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Click the Return Button

Click the Aerobic Button: The aerobic system is quite complex and the easiest way to think about it is to

break it down into three systems. The first system is easy

because it is glycolysis and is the same series of chemical

reactions that we discussed in the lactic acid system. As you

recall, glycolysis begins with stored glycogen that is just lots

of glucose molecules linked together. Glycolysis releases

enough energy to synthesize 2 ATP. It also produces 2

NADH, which is a store of energy the mitochondria can use,

and of course youve got your pyruvate. When the athlete is

using glycogen stores to produce high speed the by-product

is lactic acid. But, when the speed is much lower the aerobic

energy system removes the pyruvate and uses it as fuel. So,

the difference now is that instead of pyruvate being

converted into lactic acid it enters into the mitochondria.

Go to the next screen: The aerobic system is very important to endurance runners. Pyruvate and fatty acids are

used for fuel depending on the intensity of the run. Amino

acids from proteins can also be used but is insignificant in

healthy individuals. The first step is to convert the fuel

entering the mitochondria into acetyl CoA. From there two

further systems continue the processing the Krebs Cycle,

also known as the Citric Acid Cycle) and the electron

transport chain.

Click on the Take a look inside the

mitochondria button: Here you see all the steps contributing to aerobic energy put together. The movie clip is

showing you an inside look at the mitochondria. The Krebs

Cycle occurs in the matrix of the mitochondria and the

electron transport chain is located in the inner membrane.

Carbon dioxide is produced in the conversion of pyruvate to

acetyl CoA and the Krebs Cycle. Oxygen is used by the

electron transport chain to accept the electrons where the

byproduct is water.

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Go to the next screen: The aerobic energy system produces a lot of ATP - note that most of the ATP is

produced by the electron transport chain. The Krebs Cycle

produces 2 molecules of ATP and Glycolysis produces 2

ATP. As long as pyruvate can be cleared into the

mitochondria no lactate or hydrogen ions will accumulate.

However, the aerobic system is rather slow and depending on

their conditioning the athlete has to run less than 65 to 70%

of their max heart rate to completely clear pyruvate. At this

level most well conditioned runners will use fat as fuel. If

they run faster than 70% of their max heart rate glycolysis

must work at a faster rate and pyruvate will begin to back up.

The consequence that pyruvate will be converted to lactate

and hydrogen ions. Once again, a well-conditioned runner

can handle the acid environment until about 90% of max

heart rate but the problem is that they will be using their

limited glycogen supply. If they run out of glycogen they will hit that dreaded wall. Your endurance instructor will talk more

about this.

Go to the next screen: Here are the important points regarding the aerobic energy system. It provides a lot of

energy and the by-products are harmless. Unfortunately, its a

relatively slow ATP production mechanism but it is also the

most trainable energy system. Lactate testing is very useful

for determining the progress the athlete is making with their

training.

Go to the next screen: There are various ways you can train the aerobic system. Continuous runs are used for general

endurance; extensive tempo runs are used to train the

turnover of lactate and the bodys ability to tolerate higher

levels of acidity and intensive tempo runs train efficient

muscle fiber recruitment.

Click the Return Button

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Click the summary button: So lets summarize what we have discussed about the energy systems. First, every

active sport requires all the energy systems including the

ATP stores and the creatine phosphate system that we usually

lump together and call the ATP-CP system which is alactic,

the anaerobic glycolytic or lactic acid system and the aerobic

system. The main energy systems used depends on the nature

of the power requirements and length on time the activity

takes. Endurance runners for example will need a highly

trained aerobic system, 100 and 200 m runners will need a

highly developed glycolytic and ATP-PC system and

throwers will need a highly developed ATP-PC system.

Go to the next screen: The energy used by our bodies comes originally from the sun that is converted by plants into

chemical energy in the form of food. Inside out bodies the

energy from food is used to produce a high energy compound

call adenosine triphosphate or ATP. ATP is the basic fuel that

powers all of our bodily functions including contraction of

our muscles.

Go to the next screen: ATP consists of a molecule called adenosine that is linked to three phosphate groups by

high-energy chemical bonds. When one of these phosphate

groups breaks off energy is released. This energy is

transferred to our muscles allowing them to do work. Our

muscles contain only a limited supply of ATP that gets used

up very quickly.

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Go to the next screen: To keep muscles working ATP needs to be resynthesized by the addition a new phosphate

group. ATP resynthesis requires and input of energy provided

by chemical pathways known as energy systems. These are

the phosphocreatine system; the lactic acid (glycolytic)

energy system and the aerobic energy system. These energy

systems work continuously to replenish our supply of ATP.

Go to the next screen: Lets take a look at a summary graph the shows the timing of each energy system. As the

demand for energy increases the ATP stores are used to meet

the higher demand. As the ATP stores are used this

stimulates all energy systems to begin their ATP resynthesis

activity. The fastest energy system to gear up to speed is the

phosphocreatine energy system. However, while this energy

system rebuilds ATP very quickly and allows the athlete to

produce a very high level of power and speed it only has a

short time ability to remake ATP because of the limited store

of creatine phosphate in the muscle that this energy system

relies on. After about 5 secs the phosphocreatine system has

reached its peak activity and creatine phosphate begins to

deplete. The glycolytic energy system has now geared up

sufficiently to pick up the slack and continues to accelerate

its resynthesis of ATP. After about 15 seconds the glycolytic

energy system has reached its peak resynthesis of ATP. If the athlete wants to keep running speed will have to decrease

dramatically because the continued high use of the glycolytic system will produce an acid environment that interferes with

the ability of the muscle cell to work. By now the aerobic energy system is almost at its peak production of ATP. Each

athletes aerobic capacity will differ depending on their level of training and their ability to take on and use oxygen. If the

athlete drops the speed and runs within the capacity of the aerobic system 2 hours of running and more are possible. Note

how overall speed of performance drops as the athlete progresses from using the ATP stores then to the phosphocreatine

system, the lactic acid system and then the aerobic system.

Go to the next screen: This animation provides you with another look at the timing of the PCr, glycolytic and

aerobic energy systems. On the right of the screen is an

energy needs indicator and just below that is a lactate level

indicator. There are also three use indicators. At rest, the

aerobic energy system does the bulk to the ATP production

work. Place the cursor on the red bar to the left in the rest

location. Now slide the cursor down to the start easy exercise

location. The arm will start moving. Remember that the cell

defends its ATP store so as soon as the muscles of the arm

start using the ATP store you will note that the PCr energy

system begins to move into action. The PCr energy system

can supply ATP for about 5 secs and then you will see that

glycolysis begins to take over. Continue to slide the cursor

down the red bar and note how long it takes for the aerobic

energy system to fully gear up to speed. Also note that when

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you stimulate the arm to move faster how lactate levels rise. This is because you are moving the arm faster than the ATP

production capabilities of the aerobic energy system. Lactate levels rise and with lactate comes the hydrogen ions that case an

acidic environment for the muscle. After about 40 secs the pain becomes intolerable and the athlete must stop the action to

allow the acidity of the muscle to return to normal levels. The aerobic system is very important during the recovery process

it actually better to continue slow movement during the recovery process because the lactate and hydrogen ions will be

removed more quickly.

Click the Home Menu Button

You have now completed this module