mai article energy

8/2/2019 MAI Article Energy

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Where Energy To train Comes From

Overview

For most of our training life we simply do it without thinking about the science, or concerned

concerned with how any human physical activity is fueled. However, if we want to get the best

out of our physical capabilities we should spend some time getting to understand the

mechanics of what fuels our activity.

Essentially, we are talking about the production of energy and the first thing to know is that

this is time and intensity related. It is obvious to state that, say, running at very high intensity,

as in sprinting, means an athlete can operate effectively for only a very short period. Running

at a low intensity, as in gentle jogging, means that an athlete can sustain activity for a long

period.

Training introduces another variable, and the sprinter who uses sound training principles is

able to run at a high intensity for longer periods. Similarly, the endurance athlete who uses

sound training methods can sustain higher intensities during a set period. There is also a

relationship between the exercise intensity and the energy source.

Central to the study of exercise physiology is energy. Exercise physiologists are interested in;

Where we get our energy to exercise from.

How we optimise our energy usage during exercise

How we recover our energy stores following exercise

This unit will look at how the body converts energy from food into energy for muscularcontractions which enable us to carry out physical exercise. This knowledge allows us to better

coach ourselves, and others in the martial arts, to maximum performance.

Energy exists, as we know, in a number of different forms - electrical, light, heat and we must

first understand that energy is never lost; it is constantly recycled, often from one form to

another. Boiling a kettle transfers electrical energy to heat. Similarly, energy found in the

chemical bonds of food fuels that we eat are transformed into mechanical energy, enabling us

to move. It is the conversion of chemical energy into mechanical and heat energy that this unit

is about.


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Sources of Energy in the Body

For movement to occur, chemical energy must be transferred into mechanical energy and the

chemical energy is stored in an easy-access, energy rich compound called adenosine

triphosphate(ATP). ATP exists in all cells and consists of a number of atoms held together

by high energy bonds. It is through breaking down these bonds that energy is released. ATP is

the energy currency of cells and is the only direct source of energy for all energy-requiring

processes in the body.

When energy is required, the enzyme ATPase is released which initiates the breakdown of

ATP. It is the outermost bond of ATP that attracts ATPase as it is that bond that stores most

energy. Through the breakdown of ATP, energy is released leavingadenosine diphosphate

(ADP

)and an inorganic phosphate

(Pi). This process also gives o

ffheat and is termed

exothermic. Through the breakdown of ATP, energy is released to help the heart beat,

muscles to contract and the brain to fire electrical impulses.


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There is, however, only a limited supply of ATP within the muscle cell, probably only enough

to perform maximal exertion for two to three seconds, such as amaximal weight lift or a sprint

start. If we had to carry an unlimited supply of ATP we would have to carry the bodys

equivalent weight around with us so, more practically, the body has adapted to becoming an

ATP recycling machine.

This recycling or resynthesising of ATP itself requires energy and this comes from the food we

eat. The fuels for ATP resynthesis are derived from the following sources;

Phosphocreatine (PCr)- a high-energy compound which exists in the muscles alongside

ATP and provides the energy for ATP resynthesis during high-intensity exercise. PCr is used in

the first 10 seconds of intense exercise and the close proximity of PCr to ATP in the muscle

helps this immediate synthesis, but, like ATP PCr stores are limited.

Glycogen(stored carbohydrate)- the form of carbohydrate stored in the muscles (350g)

and liver (100g), which is first converted into glucose before being broken down to release the

energy for ATP resynthesis. It is important to know that during high-intensity exercise,

glycogen can be used without the presence of oxygen (anaerobic metabolism). However, much

more energy can be released from glycogen during aerobic metabolism (when oxygen is

present).

Triglycerides(muscular stores of fat)- at rest, up to two-thirds of our energy requirement

is met through the breakdown of fatty acids (the component of fat used for energy

production). This is because fat can provide more energy per gram than glycogen (1g of fat

provides 9.1 kcal of energy compared to 4.1 kcal of energy for every 1g of glycogen). The

downside is that fat requires 15 per cent more oxygen than glycogen to metabolise, but it

remains the favoured fuel source at rest and during endurance (long/slow) based activity. One

molecule (mole) of fatty acid typically yields around 130 moles of ATP.

Fats, as an energy source, need a plentiful supply of oxygen and the transport of fatty acids in

the blood is poor (slow) due to their insolubility, requiring the necessity for glycogen to be

present so as to provide supplementary energy for muscle contractions.

Proteins- the least favoured source of energy, only containing 5 to 10 percent of total energy

yield. In the presence of oxygen protein can be used as an energy provider if, say, glycogenstores are low. Protein facilitates growth and repair of the bodys cells, such as muscle tissue

and are its primary functions.


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The Three Pathways

The conversion, therefore, of these fuels into energy which can be used to resynthesise ATP

occurs through one of the pathways, or energy systems. Remember, it is the intensity and

duration of the exercise which dictates whether oxygen is present and, ultimately, which

system predominates. The three energy systems are;

1. ATP-PC or alactic system

2. The lactic acid system

3. The aerobic (oxidative) process

The more intense the exercise, the more the performer will rely on the production of energy

from anaerobic pathways such as the ATP-PC system, or lactic acid system. Heavy, stressful

and dynamic martial arts drills are fueled by these systems. If we separate the initial ATP

breakdown that ignites us for the first 2/3 seconds we have four pathways.


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1. The ATP-PCr (alactic)system

As we now know, ATP stores are depleted after about three seconds, so for high intensity effort

to continue, the immediate recycling of ATP is necessary, but without oxygen available (oxygen

deficit) during high intensity work, the body relies on PCr. Without getting too technical, this

breakdown takes place in the sarcoplasm(fluid that surrounds the muscle). PCr is broken

down by an enzyme, creatine kinase which will have been stimulated by the increase of

ADP and inorganic phosphate (both products of ATP breakdown as described above).

The initial ATP utilisation will be over before these athletes reach the first hurdle.

The issue to remember is that the breakdown of PCr is not used for muscle contractions, but

instead used to recycle ATP so that it can again be broken down. This reaction is known as

Endothermic. The ATP-PC system is of particular use to athletes who compete at high

intensity for about 10 seconds- such as 100m sprinters, or a martial artist performing an

intense combination of kicks and punches.

Advantages of the ATP-PC System

The resynthesis of ATP by PCr happens rapidly.

PCr stores are recovered very quickly, within 2-3 minutes of stopping exercise.

It is an anaerobic process so doesnt need to wait for three minutes for sufficient oxygen to

be present.

There are no fatiguing by-products which could delay recovery.

Creatine supplementation has been shown to extend the time usage

Drawbacks are that PCr can only be restored when oxygen is present, say, during rest and

its usage is only about the 10 sec mark. So, for a 100m sprint, ATP will initially split to enable

the athlete to drive away from the blocks, with PCr breaking down to maintain a constant

supply of energy for the rest of the race.

2. The Lactic Acid (lactate anaerobic) System

The word threshold is used to describe the point where one energy system is exhausted and

another takes over as the predominant one and for most activity that lasts longer than the 10


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second threshold of ATP-PC, the body switches to glycogen as the next fuel source to

resynthesise ATP. Stored in the liver and muscle, glycogen is first broken down into glucose

6-phosphate, before it is broken down into pyruvate(pyruvic acid) by another enzyme in

a process known as glycolysis. The glycolysis also takes place in the sarcoplasm to facilitate

ATP resynthesis. This energy process will fuel an athlete for some 1 3 minutes and a 400m

runner is an obvious example of an athlete for whom this process is the ideal energy system.

Advantages of the Lactic Acid System

Because there are few chemical reactions, ATP can be resynthesised relatively quickly for

bouts of exercise that take place between 10 secs 3 mins.

It is an anaerobic system and therefore doesnt need to wait 3 minutes for sufficient oxygen.

Any lactic acid produced as a by-product can be converted back into liver glycogen.

Even during long aerobic activities, i.e. 10k run, the lactic acid system can be called upon

to produce an extra burst of energy, for example, a sprint finish.

Drawbacks of the lactic system are first, the accumulation of lactic acid which make glycotic

enzymes acidic, causing them to lose their catalytic ability, inhibiting further energy

production by glycolysis. Activity, therefore, has to be reduced or stopped; only a small amount

of energy is locked in a glycogen molecule (approx. 5%), that can be released in the absence of

oxygen (the remaining 95% can only be released in the presence of oxygen).

3.The Aerobic System

During resting conditions, or where demands for energy is low, oxygen is readily available

(hence the name aerobic system) to release stored energy from glycogen, fats and proteins.

The aerobic system is the bodys preferred energy pathway, as it is, by far, the most effective in

terms of ATP resynthesis the yield from aerobic metabolism is some 18 times greater than

anaerobic processes.

As outlined above, under anaerobic conditions, pyruvic acid(pyruvate) is converted into a

fatigue-inducing lactic acid. However, when oxygen is present, pyruvic acid is instead

converted into acetylcoenzyme-A by combination with an enzyme with an even longername! This reaction now moves, from taking place in the sarcoplasm, to the mitochondria.


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Mitochondria are known as the powerhouse of the cell, being specialised structures within all

cells that are the site of ATP production under aerobic conditions. Mitochondria are the

ultimate destination of the oxygen that we breathe in. It is inside these factories that all our

aerobic energy is produced. The more fit we are the more and larger mitochondria we possess.

If we remember the work on the previous Unit on muscle types, it is interesting to note that

slow twitch muscle fibres house many more mitochondria than fast twitch fibres and, hence,

are more suited to aerobic activity, such as marathon running.

Two Stages of the Aerobic System

Without going into the complicated mechanisms of these two systems, we should know that

these are;

1.The Krebs Cycle

2.The Electron Transport System

As mentioned, earlier, it is not only glycogen that can be utilised in the aerobic energy system

and long, endurance exercise will use a mixture of both glycogen and fats and also, reluctantly,

protein. By preference, the body will look to fats for its greatest energy return, thereby sparing

glycogen for later in the event, when intensity may increase. Water and carbon dioxide are by-

products of these processes.

Advantages of the Aerobic System

Significantly more ATP can be resynthesised under aerobic conditions than anaerobic (36

ATP aerobically to 2 ATP anaerobically from one mole of glycogen).

The body has substantial stores of muscle glycogen and triglycerides to enable exercise to

last for hours.

Oxidation of glycogen and fatty acids do not produce any fatiguing by-products.

Drawbacks of the system are that from a resting state to exercise, it takes a while for

sufficient oxygen to become available to meet demands; although fatty acids are the fuel during

endurance events, fatty acid transport is slow and requires 15% more oxygen than required to

break down the same amount of glycogen; glycogen is required alongside fatty acids, but if it


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becomes depleted and the body attempts to metabolise fatty acids as a sole source of fuel,

muscle spasms may result commonly known as hitting the wall.

Energy Profiling

This term is used to describe the importance of each energy system to a particular activity. Inreality, the 3 energy systems work alongside each other, each contributing different amounts of

energy to resynthesise ATP. We can think of the relationship to fuel states and specific sports

in 3 blocks;

A T P - P C LA C T I C A C I D A E R O B I C

35% 35% 30%

This block diagram illustrates the energy profile of a squash player who will, largely, use

anaerobic systems during each point. However, the aerobic system will be called upon between

points and games to ensure swift recovery.

By contrast, if we thought about the energy profile of a traditional karate competitor, he or she

will spend by far the majority of his or her time utilisingthe ATP and ATPPC for an attack

or defence with if the exchange continues for more than 3 seconds - rarely are exchanges longer

than 10 seconds.

Whilst waiting to attack or defend the aerobic system may have come into play, but not if the

fight is over quickly. What should take place, prior to the fight, is a warm-up period, so as to

bring the aerobic system into play, which will then continue to function between the high

energy activity.

Improving Efciency

Whatever our particular training needs, we should try to improve the efficiency of our energy-

producing systems. There are a number of support systems that can be brought into play;

1.Glycogen Loading - favoured by endurance athletes, seeks to deplete the bodys

glycogen levels seven days prior to the event, through endurance based training and

carbohydrate avoidance and then, with three days to go, consuming a diet rich in

carbohydrates with little or no exercise.


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2.Creatine Supplementation- used to extend the threshold of the ATP-PC system by

ingesting creatine monohydrate, although some people may experience stomach

problems.

3.Soda Loading - is a method of neutralising the negative effects of lactic acid by

ingesting bicarbonate of soda, thereby increasing the bloods pH buffering it against

the effects. Again, stomach problems are likely.

4.Training - various training regimes can be used to improve the efficiency of each of the

three energy pathways. The following highlights those that have a direct impact on

ATP resynthesis, as we know that many other adaptations also occur with all

programmes.


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Some Training Regimes to Improve Efciency

E N E R G YS Y S T E M

D U R A T I O NO F

A C T I V I T Y

E X A M P L E SO F

A C T I V I T Y

T R A I N I N GM E T H O D

A D A P T A T IO N

F O L L O W I NGT R A I N I N G

ATP-PC 3 to 10

seconds

100m sprint

Gym Vault

Sprint

interval

training

Plyometrics

Weight

training

(80-95%

-

Increased

stores of ATP

and PC

Increased

activity of

ATPase and

creatinekinase

Lactic Acid

System

10 seconds to

3 minutes

400m run

100m swim

Squash rally

Interval

training

Fartlek

Weight

training

(65-80%

1RM/8-15

reps)

Circuit

Increased

stores of

muscle

glycogen

Increased

number of

glycolyticenzymes

(PFK)

Aerobic

System

Over 3 mins Marathon

Triathlon

Recovery

during events

Continuous

training

Fartlek

Distance

Interval

training

Increased

muscle

glycogen and

triglycerides

Increasednumber of

oxydative

enzymes

One way to think about energy pathways is that they are time duration restricted although

there is some disagreement about the actual threshold points, but the key issue is exercise


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intensity. We havent dealt with food types in this unit and it is up to students to make their

own links between food types and energy sources.

In later units we will look at combat training and fitness routines and the factors that

contribute to successful performance, irrespective of its nature. We may be coaching full

contact competitors, police officers, members of the public with little, or no physical activity

history, or particularly fit individuals, but who are not fit specific for high intensity combat

oriented drills.

Peter Consterdine can be contacted at the British Combat Association

www.britishcombatassociation.co.uk and also atwww.peterconsterdine.com
http://www.peterconsterdine.com/http://www.peterconsterdine.com/http://www.britishcombatassociation.co.uk/http://www.britishcombatassociation.co.uk/

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