To study how to improve an individuals fitness and correct illness, it is important to know which energy system is triggered at what moment. This knowledge enables one to extract maximum effort without undue stress. Thus, a briefing about energy systems in the human body.

1. Energy Systems In Human Body
Presented by,
Dr. Priti Rajak
M.P.Th.
Cardio-Respiratory
Physiotherapy

2. “ENERGY”
• Is defined as the ABILITY or
CAPACITY to do WORK.
• It is expressed in JOULES, as
Energy = work/time

4. Cells don’t get Energy directly from food, it
must be broken down into:
ATP -Adenosine Triphosphate
ATP = a form of energy one can immediately
use, it is needed for cells to function &
muscles to contract

5.  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

6.  ATP (2-3 seconds)
ATP-CP Energy System (8-10second)
Anaerobic Energy System (2-3 minutes)
Aerobic Energy System (3 minutes +)
Predominant Energy
Pathways

7. ATP-CP Energy System
 ATP is stored in the muscle & liver for “Quick
Energy”
 Nerve impulses trigger breakdown of ATP into
ADP
 ADP = Adenosine Diphosphate & 1 Phosphate
The splitting of the Phosphate bond = Energy for
work
 Ex. Muscle Contraction, Moving hand from a
hot stove, Jumping &Throwing

8. The ATP Molecule
a. Adenosine Triphosphate (ATP)
Adenosine P
PPP
PP P
b. The breakdown of ATP:
Adenosine PP
PP PPP
Energy
Energy for cellular function
ATP = ADP + energy for biological work + P
(ADP = Adenosine Diphosphate)

9. For contractions to continue… ATP must be
REBUILT
This comes from the splitting of CP
(Creatine Phosphate a Hi energy source,
automatic)
When ATP is used – it is rebuilt – as long
as there is CP
Energy released from CP breaking down,
resynthesizes the ADP & P

10. REMEMBER – only small amounts of ATP
are stored = only 2-3 sec. of Energy
ATP-CP = 8-10 sec. of Energy
The usefulness isn’t the AMOUNT of
Energy but the QUICK & POWERFUL
movements
For longer periods of work = The
Aerobic & Anaerobic Energy System must
be utilized

11. The Immediate Resynthesis of ATP by CP
a. Creatine Phosphate (CP)
Creatine
P
High energy bond
b. CP = Creatine + energy for resynthesis of ATP + P
Creatine P
Energy
c. ADP + energy from CP + P = ATP (reversal of ATP = ADP + P + energy for work)
Adenosine P
PP
P

13. Anaerobic Energy
System
 Without oxygen = Activities that require a
large burst of energy over a short period of
time
Anaerobic Glycolysis = Production of ATP
from Carbohydrates without oxygen
(breakdown of glucose)

14.  Since glycogen is stored in the muscle &
liver, it is available quickly
 This system provides ATP when ATP-CP
runs out.
 Again, ATP-CP lasts for a few seconds, the
 Anaerobic Energy System allows for 2-3
minutes of work

15. 1.The process to produce ATP is not as fast
as ATP-CP, which makes muscle
contraction slower
2.When oxygen is not present the end
product of glycolysis is lactic acid, which
causes the muscles to fatigue
3. Anaerobic Glycolysis is less efficient in
producing ATP than Aerobic Glycolysis,
BUT is needed for a large burst of energy
lasting a few minutes

17. Without Oxygen
Glucose = 2ATP + 2LA
(digested component of carbohydrates)
Glycogen = 3ATP + 2LA
(the storage form of glucose)

19. Aerobic System uses oxygen to break down
food fuels. This gives off a high energy yield.
 Carbohydrates and fats are used.
 Three stages of the aerobic pathway
are…….

29. • ATP must be re-formed from
ADP+Pi. This required energy!
• The energy comes from breaking
down Glycogen.
• Breaking down glycogen is called
Glycolysis.
• The LA system does this without
02 and is therefore refereed to as
anaerobic glycolysis.
• Because there is no 02 present the
glycogen is not totally broken down
and the by-product lactic acid is

30. Soooooo….
• Lactic acid present in the muscle
decreases muscle pH, which in turn
decreases the amount on glycolytic
enzymes and the rate of ATP resynthesis,
causing FATIGUE!
• Glycolytic enzymes are responsible for
breaking down glycogen.

31. • As we exercise pyruvate is formed
• When insufficient oxygen is available to breakdown the
pyruvate then lactate is produced
• Lactate enters the surrounding muscle cells, tissue and blood
• The muscle cells and tissues receiving the lactate either
breakdown the lactate to fuel (ATP) for immediate use or use
it in the creation of glycogen
• The glycogen then remains in the cells until energy is
required
• 65% of lactic acid is converted to carbon dioxide and water,
20% into glycogen, 10% into protein and 5% into glucose.

32. • The process of lactic acid removal takes approx. one hour, but
this can be accelerated by undertaking an appropriate warm
down that ensures a rapid and continuous supply of oxygen to
the muscles.
• The normal amount of lactic acid circulating in the blood is
about 1 to 2 millimoles/litre of blood. The onset of blood
lactate accumulation (OBLA) occurs between 2 and 4
millimoles/litre of blood. In non athletes this point is about
50% to 60% VO2 max and in trained athletes around 70% to
80% VO2 max.

33. • Lactic acid (lactate) is not:
• responsible for the burn in the leg muscles when
exercising very fast
• responsible for the soreness you experience in the 48
hours following a hard session
• a waste product
• Lactate, which is produced by the body all day long,
is resynthesized by the liver (Cori Cycle) to form
glucose that provides you with more energy. Sounds
like a friend to me.

34. • The breakdown of glucose or glycogen produces
lactate and hydrogen ions - for each lactate
molecule, one hydrogen ion is formed. The presence
of hydrogen ions, not lactate, makes the muscle
acidic that will eventually halt muscle function. As
hydrogen ion concentrations, increase the blood and
muscle become acidic. This acidic environment will
slow down enzyme activity and ultimately the
breakdown of glucose itself. Acidic muscles will
aggravate associated nerve endings causing pain and
increase irritation of the central nervous system. The
athlete may become disorientated and feel
nauseous.
Hydrogen ions

35. Improving your Lactate Threshold
• The aim is to saturate the muscles in lactic acid that
will educate the body's buffering mechanism
(alkaline) to deal with it more effectively. The
accumulation of lactate in working skeletal muscles is
associated with fatigue of this system after 50 to 60
seconds of maximal effort. Sessions should comprise
of one to five reps (depends on the athlete's ability)
with near to full recovery.

36. • Training continuously at about 85 to
90% of your maximum heart rate for
20 to 25 minutes will improve your
LT.

37. • A session should be conducted once a week
and commence eight weeks before a major
competition. This will help the muscle cells
retain their alkaline buffering ability.
Improving your LT will also improve your
duration of VO2max.