The document discusses the three main energy systems - ATP-PC system, anaerobic glycolytic system, and aerobic system - that the body uses to produce energy for exercise and sport. The ATP-PC system uses creatine phosphate to rapidly regenerate ATP for intense bursts of activity lasting 10 seconds or less. The anaerobic glycolytic system produces lactic acid as a byproduct for activities lasting 1-2 minutes. The aerobic system uses oxygen to break down carbohydrates and fats for sustained lower intensity exercise. The document provides details on the biochemical processes and energy contributions of each system.

1. 3.2. Basic Energy Systems in Sport and Exercise
•Energy is best understood as the ability to perform work (or exercise).
•The concepts of work and energy are directly related. As work
increases, so does the transfer of energy.
 The ability to run, walk, lift weights, play sport and in fact
sustain every bodily function depends on the ability of the body
to extract chemical energy from the breakdown of the food
nutrients that we consume.
2.1 Source of energy in Sport and Exercise
•Energy for our body in sport and exercise comes from the food we eat
(animal and plant sources), which provides energy-rich nutrients in the
form of carbohydrates, fats, and proteins.

2. • Carbohydrates are an important energy source for both intense
and prolonged exercise, and
• It is stored as glycogen in both the muscle where it is needed
as an energy source and in liver where the glucose is pushed
out into the blood.
• In comparison with lipid stores, carbohydrates are limited with
a total amount of approximately 500 g in the body.
• The muscle contains around 300 g of glycogen, although this
store can increase to 500 or 600 g when carbohydrate loaded,
whilst the liver glycogen stores are about 150 g in total.

3. • The liver glycogen stores are also affected by diet and exercise in
so far as these stores are enhanced by high carbohydrate feeding
and depleted by either prolonged exercise or fasting.
• The amount of energy contained within the carbohydrate stores
can be estimated by multiplying the total amount in grams by 3.75
kcal or 16 kJ.
• Therefore 300 g muscle glycogen content contains 1125 kcal or
4800 kJ of energy.

4. What are the energy systems?
• In order to extract the energy from the foods we eat and
turn it into the chemical energy that our bodies can use,
we have three separate energy production systems,
these are the:
1. ATP-PC system
2. Anaerobic glycolytic system
3. Aerobic system

5. 1. Adenosine Triphosphate (ATP)
• Structurally, ATP is composed of a carbon-nitrogen base called
adenine, a 5-carbon sugar called ribose, and three phosphates,
symbolized by Pi (inorganic phosphate).
• The ATP energy reaction is reversible. When ATP is synthesized
from ADP and Pi, energy is required. The addition of Pi is
known as phosphorylation.
ADP + Pi + energy → ATP
• When ATP is broken down, energy is released.
• Hydrolysis is a chemical process in which a substance is split
into simpler compounds by the addition of water.
• ATP is split by hydrolysis.
• ATP → ADP + Pi + energy for work + heat

6. • ATP can be resynthesized from ADP in three ways:
1. By interaction of ADP with CP (creatine phosphate,
which is sometimes designated as PC, or phosphocreatine).
2. By anaerobic respiration in the cell cytoplasm.
3. By aerobic respiration in the cell mitochondria
• Phosphocreatine is another high-energy compound stored in
muscles. It transfers its phosphate—and, thus, its potential
energy—to ADP to form ATP, leaving creatine:
ADP + PC → C + ATP

7. • Resting muscle contains more CP (~20 mmol.kg−1) and C (~12
mmol.kg−1) than ATP.
• The maximal rate of ATP resynthesis from CP is approximately
2.6 mmol.kg.sec−1 and occurs within 1–2 seconds of the onset
of maximal contraction.
• PC stores are used to regenerate ATP, and in a working muscle
will be depleted in 15–30 seconds.
• The ATP-PC system predominates in activities lasting 10
seconds or less. Since the ATP-PC system is involved primarily
at the onset of longer activities, it becomes a smaller portion of
the total energy supply as the duration gets longer.

8. 2. Anaerobic Metabolism During Exercise

9. What is Anaerobic Metabolism?
• Anaerobic metabolism (ATP-PC and LA) predominates in
supplying energy for exercises lasting between 1 and 2
minutes. The equal contribution point for anaerobic and
aerobic energy contribution to maximal exercise is probably
close to 75 seconds.
• However, even exercises lasting as long as 10 minutes use at
least 15% anaerobic sources. Within the anaerobic component
the longer the duration, the greater the relative importance of
the lactic acid system is in comparison to the phosphagen
system.

10. Cont..
• Phosphagens, also known as macroergic
compounds, are high energy storage compounds, also
known as high-energy phosphate compounds, chiefly
found in muscular tissue in animals
• Adenosine triphosphate (ATP) is the way your body
uses biochemicals to store and use energy.
• The ATP levels and creatine phosphate levels working
together are called the phosphagen system.
• This phosphagen system supplies the energy needs of
working muscle, but only for 8 to 10 seconds.

11. Cont..
• Anaerobic metabolism is the creation of energy through the
combustion of carbohydrates in the absence of oxygen.
• This occurs when your lungs cannot put enough oxygen into
the bloodstream to keep up with the demands of your muscles
for energy.
• It generally is used only for short bursts of activity, such as
when you sprint when running or cycling or when you are
lifting heavy weights.
• The end products of anaerobic respiration are lactic acid,
carbon dioxide, and water.

12. What Happens During Anaerobic Exercise?
• Anaerobic metabolism produces lactic acid, which can build up in
the muscles to the point where you "feel the burn." This burning
sensation is a normal side effect of anaerobic metabolism.
• Fast twitch muscle fibers rely more on anaerobic metabolism for
quick contractions, but they fatigue more quickly as well.
• High-intensity intervals turn a normally aerobic exercise like
endurance running into an anaerobic exercise.
• Anaerobic metabolism is needed once you exceed 90% of
maximum heart rate.

13. 3. Aerobic Metabolism during exercise
• Aerobic metabolism fuels most of the energy needed for long
duration activity. It uses oxygen to convert nutrient
(carbohydrates, fats, and protein) to ATP.
• This system is a bit slower than the anaerobic systems because it
relies on the circulatory system to transport oxygen to the working
muscles before it creates ATP.
• Aerobic metabolism is used primarily during endurance exercise
which is generally less intense and can continue for long periods
of time.
• .

14. Cont..
• During exercise, an athlete will move through these metabolic
pathways. As exercise begins, ATP is produced via anaerobic
metabolism.
• With an increase in breathing and heart rate, there is more oxygen
available and aerobic metabolism begins and continues until the
lactate threshold is reached.
• If this level is surpassed, the body cannot deliver oxygen quickly
enough to generate ATP and anaerobic metabolism kicks in again.
• Since this system is short-lived and lactic acid levels rise, the
intensity cannot be sustained and the athlete will need to decrease
intensity to remove lactic acid build-up.

15. How Your Body Uses Aerobic Metabolism?
The body uses aerobic metabolism for energy throughout the day to
fuel regular activity by the cells, muscles, and organs. This is why
you have a basal metabolic rate, a level of calorie-burning needed
just to maintain the normal body functions, apart from physical
activity calories burned.
A living body is always burning some calories, even at rest.
• Aerobic metabolism is also why your lungs absorb oxygen to be
carried by hemoglobin in the blood to your tissues.
• The oxygen is used in aerobic metabolism to oxidize
carbohydrates and the oxygen atoms end up attached to carbon
in the carbon dioxide molecule that is excreted.

16. Cont..
• The only by products of the process of aerobic metabolism of
carbohydrates are carbon dioxide and water.
• Your body disposes of these by breathing, sweating and
urinating. Compared with anaerobic metabolism, which
produces lactic acid as well, the by products of aerobic
metabolism are easier to remove from the body. This means
less muscle soreness after exercise with aerobic metabolism.

17. • Why You Want to Use Aerobic Metabolism in Exercise?
• An aerobic exercise is done at a heart rate below 85% of maximum
heart rate and doesn't use vigorous muscle contractions.
• Your body is able to maintain a constant energy stream by
breaking down carbohydrates and fats with aerobic metabolic
processes.
• At a moderate-intensity level of exercise, you are breathing
enough and your muscles' need for ATP is slow and steady enough
that you can break down glycogen into glucose and mobilize
stored fat to break down for energy.
• You can also take in carbohydrate that the body can use before all
of the stores are depleted. Athletes who get this wrong
experience bonking or "hitting the wall."