Energy systems.
PHYSIOLOGICAL
REQUIREMENTS OF
PHYSICAL ACTIVITY
Foods
Fuel and
Energy Systems
Food Fuels our Body
1. CARBOHYDRATES
(Glycogen)
2. PROTEIN
3. FATS
CARBOHYDRATES
Cereals
Pastas
Rice
Fruit/Veges
Breads
Sugar
Carbohydrates are stored as Glycogen in Muscle & Liver
CHO is the body’s preferred fuel during Exercise
– breaks down easily, uses little oxygen
PROTEIN
Fish
Red Meat
Eggs
Dairy
products
Poultry
GRAINS
Protein is stored as MUSCLE and AMINO ACIDS around the body.
5-10% contribution to endurance events:
Mainly used for growth/repair
FATS
Butter
Oils
Margarine
Cheese
Nuts
Food that we ingest is stored and burnt to fuel
our muscles
This food must be converted
into a chemical compound
called ATP
Without ATP - Muscles
cannot contract
ATP is used in all 3 energy
systems.
The type of energy system used
and the interplay between them
depends on the frequency,
duration, intensity of the activity
and fitness levels of the individual.
The 3 energy systems

The ATP – PC system




The Lactic Acid Systems



Alactacid system
Creatine phosphate system
Phosphagen system.
Anaerobic glycolysis system
Lactacid system
Aerobic System

Aerobic Glycolysis
For activity lasting:
0-10 SEC
ATP-PC
SYSTEM
10-30/40 SEC
Anaerobic
Glycolytic
SYSTEM
2MINS +
AEROBIC
SYSTEM
High Energy Phosphate System
ATP-PC
SYSTEM
Used for high
intensity
Jumps, Throws,
Sprints
Uses stores of
CP (Creatine
Phosphate) to
REMAKE ATP
CP instantly
available, but
runs out
quickly
Only have 10
seconds of CP
in muscles
If activity lasts longer than 10 sec, ATP must be
REMADE by some other means…..
Anaerobic Glycolytic
SYSTEM
Body uses stored fuel of
GLYCOGEN to REMAKE ATP
Need Oxygen to
do this properly
About 2-3
hours of
glycogen
stored in
body.
Downside –
by-product
called Lactate.
Hydrogen
Ions also
released
which inhibit
muscle
contraction
Happens because of lack
of enough Oxygen to
break down Glycogen
400m run, 800m at high intensity
The Anaerobic Glycolytic System
Anaerobic Threshold



The exercise intensity at which lactic acid begins to accumulate
within the blood
The point during exercise where the person begins to feel
discomfort and burning sensations in their muscles
Lactic acid is used to store pyruvate and hydrogen ions until
they can be processed by the aerobic system
AEROBIC SYSTEM
Like the LA system,
the Aerobic uses
Glycogen to
remake ATP.
Will keep suppling ATP
for as long as Fitness
levels allow
Used in
longer, submax
activities.
Long run,
swim, cycle.
Plenty of
Oxygen
available to
remake ATP .
So no LA or H+
is accumulated
Oxygen supply
meets demand
We use this
system at REST
(Now!) – except
we burn…
FAT!!!!
Aerobic Oxidative System
The Aerobic Oxidative System



The most important energy system in the human body
Blood lactate levels remain relatively low (3-6mmol/L bl)
Primary source of energy (70-95%) for exercise lasting longer
than 10 minutes provided that:
a) working muscles have sufficient mitochondria to meet energy
requirements
b) sufficient oxygen is supplied to the mitochondria
c) enzymes or intermediate products do not limit the Kreb’s cycle

Primary source of energy for the exercise that is performed at
an intensity lower than that of the anaerobic oxidative system
Cori Cycle

Lactic acid is taken to the liver to be
metabolized back into pyruvic acid and then
glucose
During REST
Any rest, short
OR Long, CP is
being
replenished, so
we can ‘sprint’
again.
BUT, need 3
minutes rest to
get all CP
back!
Any Lactate and Hydrogen Ions are
removed from muscles & blood stream
too.
Things to remember:
The 3 Energy
Systems are not like
TRAFFIC LIGHTS.
One does not switch
off and another goes
on.
All 3 turn on at
once no matter
what the
activity.
However, depending on
intensity and duration of the
activity, ONE system will
contribute more than the
other TWO.
The Role of Three Energy Systems During an All-out
Exercise Activity of Different Duration
Discussion Questions:
1. What are the differences between the 3 energy systems?
2. List one advantage and one disadvantage of each of the 3 energy
systems.
3. Give an example of three activities or sports that use each of (a) the
high energy phosphate system, (b) the anaerobic glycolytic system,
and (c) the aerobic oxidative system as their primary source of energy
(one sport for each energy system).
4.
What is the most important source of fuel in the body for all types of
energy production - a substance also known as the energy currency of
the body?
5.
5. Describe how each of the three energy systems could be trained
most efficiently.